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Sample records for flow-injection amperometric detection

  1. Determination of cyanide in microsamples by means of capillary flow injection analysis with amperometric detection

    Energy Technology Data Exchange (ETDEWEB)

    Backofen, U. [Leipzig Univ. (Germany). Sektion 8 - Chemie; Matysik, F.-M. [Department of Chemistry, University of Coimbra (Portugal); Werner, G. [Leipzig Univ. (Germany). Sektion 8 - Chemie

    1996-10-01

    A new approach for determining cyanide in microsamples is described. The method is based on capillary flow injection analysis (CFIA) with amperometric detection. The sensing electrode is a silver-plated microdisk electrode, where cyanide can react under formation of a dicyanoargentate complex. A remarkably low mass detection limit of 231 fmol cyanide is obtained for an injection volume of 60 nl. The sample throughput of the CFIA-arrangement is comparable with a conventional sized FIA-system. A practical application is given by analyzing the cyanide (amygdalin) concentration in apple kernels. (orig.). With 5 figs.

  2. Development of flow injection method for indirect copper determination with amperometric detection in drinking water samples

    Directory of Open Access Journals (Sweden)

    Nikolić-Mandić Snežana

    2012-01-01

    Full Text Available A gas-diffusion flow injection method with amperometric detection for indirect copper determination on a silver electrode is developed. The flow through system is equipped with two injection valves and a gas-diffusion unit. In the first step, a signal of cyanide solution was recorded. In the following step a signal of cyanide in the presence of copper was measured. Interferences (Cd(II, Co(II, Ag(I, Ni(II, Fe(III, Hg(II and Zn(II were investigated and successfully removed. The calibration graph is linear in the range 1-90 μmol dm-3 of copper, correlation coefficient is 0.993, the regression equation is I = (0.0455±0.0015c + (0.4611±0.0671, I is relative signal decrease in μA and c is concentration in μmol dm-3. Relative standard deviation for six consecutive injections of 30 μmol dm-3 copper(II was 1.47 % and for 1 μmol dm-3 copper(II was 3.40 %. The detection limit, calculated as 3 s/m (where s is a standard deviation of nine measurement of a reagent blank and m is the slope of the calibration curve, was 0.32 μmol dm-3, which corresponds to 2.44 ng of copper(II (loop volume was 0.12 cm3. The method enables 60 analyses per hour and it was successfully applied on determination of copper in drinking water samples. [Acknowledgements. The authors acknowledge the grant from the Ministry of Education and Science of the Republic of Serbia, Project number 172051

  3. Comparison of lead dioxide and cerium dioxide as mediators for carbon paste electrodes in flow injection-amperometric detection of hydrogen peroxide

    OpenAIRE

    Mihić-Necin, Bojana; Guzsvány, Valéria; Kalcher, Kurt

    2010-01-01

    Carbon paste electrodes (graphite / paraffin oil), bulk-modified with lead dioxide and cerium dioxide, were used as sensors for the amperometric determination of hydrogen peroxide in flow injection analysis. Experimental parameters, such as applied working potential, flow rate of the carrier and injection volume were optimized with a thin-layer flow-through cell. The method was validated with respect to calibration curve, linear dynamic range, detection limit, repeatability and...

  4. Electroanalysis of sulfonamides by flow injection system/high-performance liquid chromatography coupled with amperometric detection using boron-doped diamond electrode.

    Science.gov (United States)

    Preechaworapun, Anchana; Chuanuwatanakul, Suchada; Einaga, Yasuaki; Grudpan, Kate; Motomizu, Shoji; Chailapakul, Orawon

    2006-02-28

    Sulfonamides (SAs) were electrochemically investigated using cyclic voltammetry at a boron-doped diamond (BDD) electrode. Comparison experiments were carried out using a glassy carbon electrode. The BDD electrode provided well-resolved oxidation, irreversible cyclic voltammograms and higher current signals when compared to the glassy carbon electrode. Results obtained from using the BDD electrode in a flow injection system coupled with amperometric detection were illustrated. The optimum potential from a hydrodynamic voltammogram was found to be 1100mV versus Ag/AgCl, which was chosen for the HPLC-amperometric system. Excellent results of linear range and detection limit were obtained. This method was also used for determination of sulfonamides in egg samples. The standard solutions of 5, 10, and 15ppm were spiked in a real sample, and percentage of recoveries was found to be between 90.0 and 107.7.

  5. Flow-injection amperometric glucose biosensors based on graphene/Nafion hybrid electrodes

    Energy Technology Data Exchange (ETDEWEB)

    Choi, Bong Gill, E-mail: k1811@kaist.ac.kr [Department of Chemical and Biomolecular Engineering (BK21 Program), KAIST, Daejeon 305-701 (Korea, Republic of); Im, Jinkyu, E-mail: JINQ@paran.com [Department of Chemistry and Research Institute of Basic Sciences, Kyung Hee University, 1 Hoegidong, Dongdamoongu, Seoul (Korea, Republic of); Kim, Hoon Sik, E-mail: khs2004@khu.ac.kr [Department of Chemistry and Research Institute of Basic Sciences, Kyung Hee University, 1 Hoegidong, Dongdamoongu, Seoul (Korea, Republic of); Park, HoSeok, E-mail: phs0727@khu.ac.kr [Department of Chemical Engineering, College of Engineering, Kyung Hee University, 1 Seochon-dong, Giheung-gu, Youngin-si, Gyeonggi-do 446-701 (Korea, Republic of)

    2011-11-30

    Graphical abstract: Amperometric biosensors based on graphene hybrids showed the fast, sensitive, and stable amperometric responses in the flow injection system for automatically monitoring glucose. Display Omitted Highlights: > Flow-injection amperometric glucose biosensors were fabricated using reduced graphene oxide/Nafion hybrids. > The electrochemical kinetics of biosensors were comprehensively investigated by analysing electron transfer rate, charge transfer resistance, and ion diffusion coefficient, respectively. > The biosensors exhibited the fast, sensitive, and stable amperometric responses in the flow injection system for detecting glucose. - Abstract: In this research, we demonstrated the fabrication of flow-injection amperometric glucose biosensors based on RGO/Nafion hybrids. The nanohybridization of the reduced graphene oxide (RGO) by Nafion provided the fast electron transfer (ET) for the sensitive amperometric biosensor platforms. The ET rate (k{sub s}) and the charge transfer resistance (R{sub CT}) of GOx-RGO/Nafion hybrids were evaluated to verify the accelerated ET. Moreover, hybrid biosensors revealed a quasi-reversible and surface controlled process, as confirmed by the low peak-to-peak ({Delta}E{sub p}) and linear relations between I{sub p} and scan rate ({nu}). Hybrid biosensors showed the fast response time of {approx}3 s, the sensitivity of 3.8 {mu}A mM{sup -1} cm{sup -2}, the limit of detection of 170 {mu}M, and the linear detection range of 2-20 mM for the flow-injection amperometric detection of glucose. Furthermore, interference effect of oxidizable species such as ascorbic acid (AA) and uric acid (UA) on the performance of hybrid biosensors was prevented at the operating potential of -0.20 V even under the flow injection mode. Therefore, the fast, sensitive, and stable amperometric responses of hybrid biosensors in the flow injection system make it highly suitable for automatically monitoring glucose.

  6. Development of a chromatographic low pressure flow injection system using amperometric detection: Application to the analysis of niacin in coffee.

    Science.gov (United States)

    Santos, João Rodrigo; Rangel, António O S S

    2015-11-15

    In this work, an analytical flow system able to perform low pressure chromatography with amperometric detection is presented. As case study, the determination of niacin (vitamin B3) in coffee brewed samples was selected. The manifold comprised a 1.0 cm length monolithic column coated with didecyldimethylammonium bromide, a laboratory-made boron doped diamond electrode, and featured in-line ionic strength adjustment of the mobile phase. The figures of merit concerning the selected case study namely, detection limit, 7.90 × 10(-7) M, determination rate, ca. 10 samplesh(-1), mobile phase and ISA solution consumption, ca. 2.6 mL per analysis, and CV, below 5% for retention time and peak height, showed the competitiveness of this analytical strategy comparing to the described HPLC methods for niacin determination. The strategy displays a simple configuration, low cost, fast and easy assembling, foreseeing its use to general purpose applications.

  7. Amperometric detection of acetaminophen by an electrochemical sensor based on cobalt oxide nanoparticles in a flow injection system

    Energy Technology Data Exchange (ETDEWEB)

    Razmi, Habib, E-mail: h.razmi@azaruniv.ed [Electrochemistry Research Laboratory, Faculty of Sciences, Azarbaijan University of Tarbiat Moallem, P.O. Box 53714-161, Tabriz (Iran, Islamic Republic of); Habibi, Esmaeil [Electrochemistry Research Laboratory, Faculty of Sciences, Azarbaijan University of Tarbiat Moallem, P.O. Box 53714-161, Tabriz (Iran, Islamic Republic of)

    2010-12-01

    This paper reports the use of a carbon ceramic electrode as a highly-porous substrate for the electrochemical formation of cobalt oxide nanoparticles. The electrocatalyst was characterized by energy dispersive X-ray (EDX) spectroscopy, scanning electron microscopy (SEM) and cyclic voltammetry techniques, and it was used in a homemade flow injection analysis (FIA) system for acetaminophen determination using 0.1 M KOH as the carrier solution. The rate constant (k{sub s}) and charge transfer coefficient ({alpha}) were calculated for the electron exchange reaction of the modified film. The kinetic parameters and the mechanism of acetaminophen electrooxidation at the electrode surface were studied by cyclic voltammetry and chronoamperometry. The effects of working potential and flow rate on the performance of the FIA system were studied. Under optimized conditions, the electrode response due to the electrocatalytic oxidation of acetaminophen at 450 mV (vs. SCE) is proportional to the concentration of acetaminophen over a 5-35 {mu}M range with an associated detection limit (S/N = 3) of 0.37 {mu}M and a sensitivity of 0.0296 {mu}A/{mu}M. The relative standard deviation (RSD) was 1.6% for eight replicate measurements. The modified electrode was used to determine the acetaminophen content in tablet samples.

  8. Flow injection analysis using carbon film resistor electrodes for amperometric determination of ambroxol.

    Science.gov (United States)

    Felix, Fabiana S; Brett, Christopher M A; Angnes, Lúcio

    2008-06-30

    Flow injection analysis (FIA) using a carbon film sensor for amperometric detection was explored for ambroxol analysis in pharmaceutical formulations. The specially designed flow cell designed in the lab generated sharp and reproducible current peaks, with a wide linear dynamic range from 5x10(-7) to 3.5x10(-4) mol L(-1), in 0.1 mol L(-1) sulfuric acid electrolyte, as well as high sensitivity, 0.110 Amol(-1) L cm(-2) at the optimized flow rate. A detection limit of 7.6x10(-8) mol L(-1) and a sampling frequency of 50 determinations per hour were achieved, employing injected volumes of 100 microL and a flow rate of 2.0 mL min(-1). The repeatability, expressed as R.S.D. for successive and alternated injections of 6.0x10(-6) and 6.0x10(-5) mol L(-1) ambroxol solutions, was 3.0 and 1.5%, respectively, without any noticeable memory effect between injections. The proposed method was applied to the analysis of ambroxol in pharmaceutical samples and the results obtained were compared with UV spectrophotometric and acid-base titrimetric methods. Good agreement between the results utilizing the three methods and the labeled values was achieved, corroborating the good performance of the proposed electrochemical methodology for ambroxol analysis.

  9. Biomonitoring of Organophosphorus Agent Exposure by Reactivation of Cholinesterase Enzyme Based on Carbon Nanotube-Enhanced Flow-Injection Amperometric Detection

    Energy Technology Data Exchange (ETDEWEB)

    Du, Dan; Wang, Jun; Smith, Jordan N.; Timchalk, Charles; Lin, Yuehe

    2009-11-15

    A portable, rapid, and sensitive assessment of sub-clinical organophosphorus (OPs) agent exposure based on reactivation of cholinesterase (ChE) from OP-inhibited ChE using rat saliva (in vitro) was developed using an electrochemical sensor coupled with a microflow-injection system. The sensor was based on a carbon nanotube (CNT)-modified screen printed carbon electrode (SPE), which was integrated into a flow cell. Due to the extent of inter-individual ChE activity variability, ChE biomonitoring often requires an initial base-line determination (non-inhibited) of enzyme activity which is then directly compared with activity after OP exposure. This manuscript described an alternative strategy where reactivation of the phosphorylated enzyme was exploited to enable measurement of both inhibited and baseline ChE activity (i.e. after reactivation) in the same sample. The use of CNT makes the electrochemical detection of the products from enzymatic reactions more feasible with extremely high sensitivity and at low potentials. Paraoxon was selected as a model OP compound for in vitro inhibition studies. Some experiment parameters, (e.g. inhibition and reactivation times), have been optimized such that, 92 - 95% ChE reactivation can be achieved over a broad range of ChE inhibition (5 - 94 %) with paraoxon. The extent of enzyme inhibition using this electrochemical sensor correlates well with conventional enzyme activity measurements.

  10. Flow-Injection Amperometric Determination of Tacrine based on Ion Transfer across a Water–Plasticized Polymeric Membrane Interface

    OpenAIRE

    Rueda, C.; Joaquin A. Ortuño

    2007-01-01

    A flow-injection pulse amperometric method for determining tacrine, based on ion transfer across a plasticized poly(vinyl chloride) (PVC) membrane, was developed. A four-electrode potentiostat with ohmic drop compensation was used, while a flow-through cell incorporated the four electrodes and the membrane, which contained tetrabutylammonium tetraphenylborate. The influence of the applied potential and of the flow-injection variables on the determination of tacrine was studied. In the selecte...

  11. Flow injection amperometric determination of persulfate in cosmetic products using a Prussian Blue film-modified electrode

    Directory of Open Access Journals (Sweden)

    Nelson R. Stradiotto

    2003-09-01

    Full Text Available A flow-injection system with a glassy carbon disk electrode modified with Prussian Blue film is proposed for the determination of persulfate in commercial samples of hair bleaching boosters by amperometry. The detection was obtained by chronoamperometric technique and the sample is injected into the electrochemical cell in a wall jet configuration. Potassium chloride at concentration of 0.1 mol L-1 acted as sample carrier at a flow rate of 4.0 mL min-1 and supporting-electrolyte. For 0.025 V (vs. Ag/AgCl applied voltage, the proposed system handles ca. 160 samples per hour (1.0 10-4 - 1.0 10-3 mol L-1 of persulfate, consuming about 200 μL sample and 11 mg KCl per determination. Typical linear correlations between electrocatalytic current and persulfate concentration was ca. 0.9998. The detection limit is 9.0 10-5 mol L-1 and the calculated amperometric sensibility 3.6 103 μA L mol-1. Relative standard deviation (n =12 of a 1.0 10-4 mol L-1 sample is about 2.2%. The method was applied to persulfate determination in commercial hair-bleaching samples and results are in agreement with those obtained by titrimetry at 95% confidence level and good recoveries (95 - 112% of spiked samples were found.

  12. Flow-Injection Amperometric Determination of Tacrine based on Ion Transfer across a Water–Plasticized Polymeric Membrane Interface

    Directory of Open Access Journals (Sweden)

    C. Rueda

    2007-07-01

    Full Text Available A flow-injection pulse amperometric method for determining tacrine, based onion transfer across a plasticized poly(vinyl chloride (PVC membrane, was developed. Afour-electrode potentiostat with ohmic drop compensation was used, while a flow-throughcell incorporated the four electrodes and the membrane, which containedtetrabutylammonium tetraphenylborate. The influence of the applied potential and of theflow-injection variables on the determination of tacrine was studied. In the selectedconditions, a linear relationship between peak height and tacrine concentration was foundup to 4x10-5M tacrine. The detection limit was 1x10-7M. Good repeatability was obtained.Some common ions and pharmaceutical excipients did not interfere.

  13. Flow injection based microfluidic device with carbon nanotube electrode for rapid salbutamol detection.

    Science.gov (United States)

    Karuwan, Chanpen; Wisitsoraat, Anurat; Maturos, Thitima; Phokharatkul, Disayut; Sappat, Assawapong; Jaruwongrungsee, Kata; Lomas, Tanom; Tuantranont, Adisorn

    2009-09-15

    A microfabicated flow injection device has been developed for in-channel electrochemical detection (ECD) of a beta-agonist, namely salbutamol. The microfluidic system consists of PDMS (polydimethylsiloxane) microchannel and electrochemical electrodes formed on glass substrate. The carbon nanotube (CNT) on gold layer as working electrode, silver as reference electrode and platinum as auxiliary electrode were deposited on a glass substrate. Silver, platinum, gold and stainless steel catalyst layers were coated by DC-sputtering. CNTs were then grown on the glass substance by thermal chemical vapor deposition (CVD) with gravity effect and water-assisted etching. 100-microm-deep and 500-microm-wide PDMS microchannels fabricated by SU-8 molding and casting were then bonded on glass substrate by oxygen plasma treatment. Flow injection and ECD of salbutamol was performed with the amperometric detection mode for in-channel detection of salbutamol. The influences of flow rate, injection volume, and detection potential on the response of current signal were optimized. Analytical characteristics, such as sensitivity, repeatability and dynamic range have been evaluated. Fast and highly sensitive detection of salbutamol have been achieved. Thus, the proposed combination of the efficient CNT electrode and miniaturized lab-on-a-chip is a powerful platform for beta-agonists detection.

  14. Electropolymerized poly(Toluidine Blue)-modified carbon felt for highly sensitive amperometric determination of NADH in flow injection analysis

    Institute of Scientific and Technical Information of China (English)

    Yasushi Hasebe; Yue Wang; Kazuya Fukuoka

    2011-01-01

    Poly(pheniothiazine) films were prepared on a porous carbon felt (CF) electrode surface by an electrooxidative polymerization of three phenothiazine derivatives (i.e.,Tthionine (TN), Toluidine Blue (TB) and Methylene Blue (MB)) from 0.1 mol/L phosphate buffer solution (pH 7.0).Among the three phenothiazies, the poly(TB) film-modified CF exhibited an excellent electrocatalytic activity for the oxidation of nicotinamide adenine dinucleotide reduced form (NADH) at +0.2 V vs.Ag/AgCl.The poly(TB) film-modified CF was successfully used as working electrode unit of highly sensitive amperometric flow-through detector for NADH.The peak currents (peak heights) were almost unchanged, irrespective of a carrier flow rate ranging from 2.0 to 4.1 mL/min, resulting in the measurement of NADH (ca.30 samples/hr) at 4.1 mL/min.The peak current responses of NADH showed linear relationship over the concentration range from 1 to 30 μmol/L (sensitivity: 0.318 μA/(μmol/L); correlation coefficient: 0.997).The lower detection limit was found to be 0.3 μmol/L (S/N = 3).

  15. A flow injection method for the analysis of tetracycline antibiotics in pharmaceutical formulations using electrochemical detection at anodized boron-doped diamond thin film electrode.

    Science.gov (United States)

    Wangfuengkanagul, N; Siangproh, W; Chailapakul, O

    2004-12-15

    A method using flow injection (FI) with amperometric detection at anodized boron-doped diamond (BDD) thin films has been developed and applied for the determination of tetracycline antibiotics (tetracycline, chlortetracycline, oxytetracycline and doxycycline). The electrochemical oxidation of the tetracycline antibiotics was studied at various carbon electrodes including glassy carbon (GC), as-deposited BDD and anodized BDD electrodes using cyclic voltammetry. The anodized BDD electrode exhibited well-defined irreversible cyclic voltammograms for the oxidation of tetracycline antibiotics with the highest current signals compared to the as-deposited BDD and glassy carbon electrodes. Low detection limit of 10nM (signal-to-noise ratio = 3) was achieved for each drug when using flow injection analysis with amperometric detection at anodized BDD electrodes. Linear calibrations were obtained from 0.1 to 50mM for tetracycline and 0.5-50mM for chlortetracycline, oxytetracycline and doxycycline. The proposed method has been successfully applied to determine the tetracycline antibiotics in some drug formulations. The results obtained in percent found (99.50-103.01%) were comparable to dose labeled.

  16. Analysis of Tetracycline Antibiotics Using HPLC with Pulsed Amperometric Detection

    National Research Council Canada - National Science Library

    CHAROENRAKS, Thiraporn; CHUANUWATANAKUL, Suchada; HONDA, Kensuke; YAMAGUCHI, Yoko; CHAILAPAKUL, Orawon

    2005-01-01

    The analysis of tetracycline, oxytetracyline, chlortetracycline and doxycycline by high-performance liquid chromatography with pulsed amperometric detection using an anodized boron-doped diamond thin film (BDD...

  17. Bio-bar-code functionalized magnetic nanoparticle label for ultrasensitive flow injection chemiluminescence detection of DNA hybridization.

    Science.gov (United States)

    Bi, Sai; Zhou, Hong; Zhang, Shusheng

    2009-10-07

    A signal amplification strategy based on bio-bar-code functionalized magnetic nanoparticles as labels holds promise to improve the sensitivity and detection limit of the detection of DNA hybridization and single-nucleotide polymorphisms by flow injection chemiluminescence assays.

  18. Flow injection amperometric sandwich-type aptasensor for the determination of human leukemic lymphoblast cancer cells using MWCNTs-Pdnano/PTCA/aptamer as labeled aptamer for the signal amplification.

    Science.gov (United States)

    Amouzadeh Tabrizi, Mahmoud; Shamsipur, Mojtaba; Saber, Reza; Sarkar, Saeed

    2017-09-08

    In this research, we demonstrated a flow injection amperometric sandwich-type aptasensor for the determination of human leukemic lymphoblasts (CCRF-CEM) based on poly(3,4-ethylenedioxythiophene) decorated with gold nanoparticles (PEDOT-Aunano) as a nano platform to immobilize thiolated sgc8c aptamer and multiwall carbon nanotubes decorated with palladium nanoparticles/3,4,9,10-perylene tetracarboxylic acid (MWCNTs-Pdnano/PTCA) to fabricate catalytic labeled aptamer. In the proposed sensing strategy, the CCRF-CEM cancer cells were sandwiched between immobilized sgc8c aptamer on PEDOT-Aunano modified surface electrode and catalytic labeled sgc8c aptamer (MWCNTs-Pdnano/PTCA/aptamer). After that, the concentration of CCRF-CEM cancer cells was determined in presence of 0.1 mM hydrogen peroxide (H2O2) as an electroactive component. The attached MWCNTs-Pdnano nanocomposites to CCRF-CEM cancer cells amplified the electrocatalytic reduction of H2O2 and improved the sensitivity of the sensor to CCRF-CEM cancer cells. The MWCNT-Pdnano nanocomposite was characterized with transmission electron microscopy (TEM) and energy dispersive X-ray (EDX). The electrochemical impedance spectroscopy (EIS) and cyclic voltammetry (CV) were used to confirm the stepwise changes in the electrochemical surface properties of the electrode. The proposed sandwich-type electrochemical aptasensor exhibited an excellent analytical performance for the detection of CCRF-CEM cancer cells ranging from 1.0 × 10(1) to 5.0 × 10(5) cells mL(-1). The limit of detection was 8 cells mL(-1). The proposed aptasensor showed high selectivity toward CCRF-CEM cancer cells. The proposed aptasensor was also applied to the determination of CCRF-CEM cancer cells in human serum samples. Copyright © 2017 Elsevier B.V. All rights reserved.

  19. Cost-effective flow injection amperometric system with metal nanoparticle loaded carbon nanotube modified screen printed carbon electrode for sensitive determination of hydrogen peroxide.

    Science.gov (United States)

    Reanpang, Preeyaporn; Themsirimongkon, Suwaphid; Saipanya, Surin; Chailapakul, Orawon; Jakmunee, Jaroon

    2015-11-01

    Various metal nanoparticles (NPs) decorated on carbon nanotube (CNT) was modified on the home-made screen printed carbon electrode (SPCE) in order to enhances sensitivity of hydrogen peroxide (H2O2) determination. The simple casting method was used for the electrode modification. The monometallic and bimetallic NPs modified electrodes were investigated for their electrochemical properties for H2O2 reduction. The Pd-CNT/SPCE is appropriated to measure the H2O2 reduction at a potential of -0.3 V, then this modified electrode was incorporated with a home-made flow through cell and applied in a simple flow injection amperometry (FI-Amp). Some parameters influencing the resulted modified electrode and the FI-Amp system were studied. The proposed detection system was able to detect H2O2 in the range of 0.1-1.0 mM, with detection limit of 20 µM. Relative standard deviation for 100 replicated injections of 0.6 mM H2O2 was 2.3%. The reproducibility of 6 electrodes preparing in 3 different lots was 8.2%. It was demonstrated for determination of H2O2 in disinfectant, hair colorant and milk samples. Recoveries in the range of 90-109% were observed. The developed system provided high stability, good repeatability, high sample throughput and low reagent consumption.

  20. Selective chlorine dioxide determination using gas-diffusion flow injection analysis with chemiluminescent detection

    Energy Technology Data Exchange (ETDEWEB)

    Hollowell, D.A.; Gord, J.R.; Gordon, G.; Pacey, G.E.

    1986-06-01

    An automated chemiluminescent technique has been developed utilizing the advantages of gas-diffusion flow injection analysis. A gas-diffusion membrane separates the donor (sampling) stream from the acceptor (detecting) stream and removes ionic interferences. A novel chemiluminescence flow-through detector cell is used to measure the concentration of chlorine dioxide as a function of the intensity of the chemiluminescence produced from its reaction with luminol. The chemiluminescent reagent merges with the analyte directly in front of the photomultiplier tube in order to maximize the sensitivity of the system. The detection limit for chlorine dioxide is approximately 5 ppb. The method is over 1500 times more selective for chlorine dioxide than for chlorine on a mole basis. This method eliminates interference from iron and manganese compounds, as well as other oxychlorinated compounds such as chlorite ion and chlorate ion.

  1. Bienzymatic Biosensor for Rapid Detection of Aspartame by Flow Injection Analysis

    Directory of Open Access Journals (Sweden)

    Maria-Cristina Radulescu

    2014-01-01

    Full Text Available A rapid, simple and stable biosensor for aspartame detection was developed. Alcohol oxidase (AOX, carboxyl esterase (CaE and bovine serum albumin (BSA were immobilised with glutaraldehyde (GA onto screen-printed electrodes modified with cobalt-phthalocyanine (CoPC. The biosensor response was fast. The sample throughput using a flow injection analysis (FIA system was 40 h−1 with an RSD of 2.7%. The detection limits for both batch and FIA measurements were 0.1 µM for methanol and 0.2 µM for aspartame, respectively. The enzymatic biosensor was successfully applied for aspartame determination in different sample matrices/commercial products (liquid and solid samples without any pre-treatment step prior to measurement.

  2. Bienzymatic biosensor for rapid detection of aspartame by flow injection analysis.

    Science.gov (United States)

    Radulescu, Maria-Cristina; Bucur, Bogdan; Bucur, Madalina-Petruta; Radu, Gabriel Lucian

    2014-01-09

    A rapid, simple and stable biosensor for aspartame detection was developed. Alcohol oxidase (AOX), carboxyl esterase (CaE) and bovine serum albumin (BSA) were immobilised with glutaraldehyde (GA) onto screen-printed electrodes modified with cobalt-phthalocyanine (CoPC). The biosensor response was fast. The sample throughput using a flow injection analysis (FIA) system was 40 h⁻¹ with an RSD of 2.7%. The detection limits for both batch and FIA measurements were 0.1 µM for methanol and 0.2 µM for aspartame, respectively. The enzymatic biosensor was successfully applied for aspartame determination in different sample matrices/commercial products (liquid and solid samples) without any pre-treatment step prior to measurement.

  3. Amperometric biosensor for Salmonella typhimurium detection in milk

    Science.gov (United States)

    This paper reports an amperometric biosensor for rapid and sensitive Salmonella Typhimurium detection in milk. The biosensor was assembled from the self-assembled monolayers technique on a gold surface. In this device, polyclonal antibodies were oriented by protein A. The biosensor structure was cha...

  4. The electrochemical oxidation of homocysteine at boron-doped diamond electrodes with application to HPLC amperometric detection.

    Science.gov (United States)

    Chailapakul, O; Siangproh, W; Sarada, B V; Terashima, C; Rao, Tata N; Tryk, D A; Fujishima, A

    2002-09-01

    The electrochemical oxidation of homocysteine was studied at as-deposited and anodized (oxidized) boron-doped diamond (BDD) thin film electrodes with cyclic voltammetry, flow injection analysis and high-pressure liquid chromatography with amperometric detection. At anodized boron-doped diamond electrodes, highly reproducible, well-defined cyclic voltammograms for homocysteine oxidation were obtained in acidic media, while as-deposited diamond did not provide a detectable signal. In alkaline media, however, the oxidation response was obtained both at as-deposited and anodized diamond electrodes. The potential sweep rate dependence of homocysteine oxidation (peak currents for 1 mM homocysteine linearly proportional to v(1/2), within the range of 0.01 to 0.3 V s(-1)) indicates that the oxidation involves a diffusing species, with negligible adsorption on the BDD surface at this concentration. In the flow system, BDD exhibited a highly reproducible amperometric response, with a peak variation less than 2%. An extremely low detection limit (1 nM) was obtained at 1.6 V vs. Ag/AgCl. In addition, the determination of homocysteine in a standard mixture with aminothiols and disulfide compounds by means of isocratic reverse-phase HPLC with amperometric detection at diamond electrodes has been investigated. The results showed excellent separation, with a detection limit of 1 pmol and a linear range of three orders of magnitude.

  5. Determination of iodide using flow injection with acidic potassium permanganate chemiluminescence detection.

    Science.gov (United States)

    Yaqoob, Mohammad; Atiq-ur-Rehman; Waseem, Amir; Nabi, Abdul

    2006-01-01

    A simple and rapid flow-injection method is described for the determination of iodide, based on potassium permanganate chemiluminescence detection via oxidation of formaldehyde in aqueous hydrochloric acid. The calibration graph was linear over the range 1.0-12 x 10(-6) mol/L (r2 = 0.9955) with relative standard deviations (n = 4) in the range 1.0-3.5%. The detection limit (3sigma) was 1.0 x 10(-7) mol/L, with sample throughput of 120/h. The effect of interfering cations [Ca(II), Mg(II), Ni(II), Fe(II), Fe(III) and Pb(II)] and anions (Cl-, SO4(2-), PO4(3-), NO3-, NO2-, F- and SO3(2-)) were studied. The method was applied to iodized salt samples and the results obtained in the range 0.03 +/- 0.005 - 0.10 +/- 0.006 mg I/g were in reasonable agreement with the amount labelled. The method was statistically compared with the results obtained by titration; no significant disagreement at 95% confidence was observed.

  6. Rapid detection of pesticides not amenable to multi-residue methods by flow injection-tandem mass spectrometry

    NARCIS (Netherlands)

    Mol, J.G.J.; Dam, van R.C.J.

    2014-01-01

    Flow injection combined with tandem mass spectrometry (MS/MS) was investigated for the rapid detection of highly polar pesticides that are not amenable to multi-residue methods because they do not partition into organic solvents and require dedicated chromatographic conditions. The pesticides includ

  7. Characterization of natural chitosan membranes from the carapace of the soldier crab Mictyris brevidactylus and its application to immobilize glucose oxidase in amperometric flow-injection biosensing system.

    Science.gov (United States)

    Chen, Po-Chung; Hsieh, Bo-Chuan; Chen, Richie L C; Wang, Tzu-Yu; Hsiao, Hsien-Yi; Cheng, Tzong-Jih

    2006-01-01

    This study investigated characteristics of a chitosan membrane from the carapace of the soldier crab Mictyris brevidactylus intended to construct an amperometric biosensor. Electrochemical impedance spectroscopy (EIS) and cyclic voltammetry (CV) were used in this study to characterize these chitosan membranes intended for constructing enzymatic biosensors. Chitosan membranes suffering various durations (>10 min) of deacetylation had small charge-transfer resistances (0.55 microF). They were found in EIS where both the solution resistance and Warburg impedance upon electrode interface were almost independent of the durations and degree of deacetylation. The degree of deacetylation and the thickness of chitosan membranes were also determined. Membrane thickness was slightly dependent with the duration but degree of deacetylation was slightly dependent on the duration. Chitosan membranes with various thicknesses suffered various durations of deacetylation, but this did not influence their electrochemical characteristics. The chitinous membrane was covalently immobilized with glucose oxidase (EC 1.3.4.3) and then attached onto the platinum electrode of a homemade amperometric flow cell. Sensor signal was linearly related to glucose concentration (r=0.999 for glucose up to 1.0 mM). The system was sensitive (S/N>5 for 10 microM glucose) and reproducible (CV<1.3% for 50 microM glucose, n=5).

  8. Spectrophotometric detection of arsenic using flow-injection hydride generation following sorbent extraction preconcentration.

    Science.gov (United States)

    Neto, J A; Montes, R; Cardoso, A A

    1999-12-06

    An automated system with a C(18) bonded silica gel packed minicolumn is proposed for spectrophotometric detection of arsenic using flow-injection hydride generation following sorbent extraction preconcentration. Complexes formed between arsenic(III) and ammonium diethyl dithiophosphate (ADDP) are retained on a C(18) sorbent. The eluted As-DDP complexes are merged with a 1.5% (w/v) NaBH(4) and the resulting solution is thereafter injected into the hydride generator/gas-liquid separator. The arsine generated is carried out by a stream of N(2) and trapped in an alkaline iodine solution in which the analyte is determined by the arsenomolybdenum blue method. With preconcentration time of 120 s, calibration in the 5.00-50.0 mug As l(-1) range and sampling rate of about 20 samples h(-1) are achieved, corresponding to 36 mg ADDP plus 36 mg ammonium heptamolybdate plus 7 mg hydrazine sulfate plus 0.7 mg stannous chloride and about 7 ml sample consumed per determination. The detection limit is 0.06 mug l(-1) and the relative standard deviation (n=12) for a typical 17.0 mug As l(-1) sample is ca. 6%. The accuracy was checked for arsenic determination in plant materials from the NIST (1572 citrus leaves; 1573 tomato leaves) and the results were in agreement with the certified values at 95% confidence level. Good recoveries (94-104%) of spiked tap waters, sugars and synthetic mixtures of trivalent and pentavalent arsenic were also found.

  9. Enhanced flow injection analysis for measurements of S-nitrosothiols species in biological samples using highly selective amperometric nitric oxide sensor

    Institute of Scientific and Technical Information of China (English)

    Chun Cui Huang; Hui Bo Shao

    2012-01-01

    A highly selective nitric oxide (NO) sensor is fabricated and applied to devise an enhanced flow injection analysis (FIA) system for S-nitrosothiols (RSNOs) measurement in biological samples.The NO sensor is prepared using a polytetrafluoroethylene (PTFE) gas-permeable membrane loaded with Teflon AF(R) solution,a copolymer of tetrafluoroethylene and 2,2-bis(trifluoroethylene)-4,5-difluoro-1,3-dioxole,to improve selectivity.This method is much simpler and possesses good performance over a wide range of RSNOs concentrations.Standard deviation for three parallel measurements of blood plasma is 4.0%.The use of the gas sensing configuration as the detector enhances selectivity of the FIA measurement vs.using less selective electrochemical detectors that do not use PTFE/Teflon type outer membranes.

  10. Amperometric immunosensor for rapid detection of Mycobacterium tuberculosis

    Science.gov (United States)

    Hiraiwa, Morgan; Kim, Jong-Hoon; Lee, Hyun-Boo; Inoue, Shinnosuke; Becker, Annie L.; Weigel, Kris M.; Cangelosi, Gerard A.; Lee, Kyong-Hoon; Chung, Jae-Hyun

    2015-05-01

    Tuberculosis (TB) has been a major public health problem, which can be better controlled by using accurate and rapid diagnosis in low-resource settings. A simple, portable, and sensitive detection method is required for point-of-care (POC) settings. This paper studies an amperometric biosensor using a microtip immunoassay for a rapid and low-cost detection of Mycobacterium tuberculosis (MTB) in sputum. MTB in sputum is specifically captured on the functionalized microtip surface and detected by electric current. According to the numerical study, the current signal on the microtip surface is linearly changed with increasing immersion depth. Using a reference microtip, the immersion depth is compensated for a sensing microtip. On the microtip surface, target bacteria are concentrated and organized by a coffee-ring effect, which amplifies the electric current. To enhance the signal-to-noise ratio, both the sample processing and rinsing steps are presented with the use of deionized water as a medium for the amperometric measurement. When applied to cultured MTB cells spiked into human sputum, the detection limit was 100 CFU mL-1, comparable to a more labor-intensive fluorescence detection method reported previously.

  11. Design and Development of a Microfluidic Amperometric Immunosensor for the Quantitative Detection of 2,6-dichlorobenzamide (BAM) Herbicide Residue in Ground Water

    DEFF Research Database (Denmark)

    Uthuppu, Basil

    and it is a novel characteristic of the microfluidic device prototype. The microfluidic device was automated using Lego® Mindstorms® servomotors to control its micro pumps and valves. By confirming (amperometrically) the regeneration capability of the optimized immunosurface and generating a standard curve for BAM...... the optimized BAM immunoassay and the electrochemical detection method. A modular approach was adopted for the fabrication of the microfluidic platform in order to make the device simple to integrate, automate and maintain. The microfluidic platform has an in-built micro flow-injection analysis (µFIA) system...

  12. Filterless preconcentration, flow injection analysis and detection by inductively-coupled plasma mass spectrometry

    DEFF Research Database (Denmark)

    Andersen, Jens Enevold Thaulov

    The influence of interferences in the analysis of elements by inductively-coupled-plasma mass-spectrometry (ICP-MS) may be significantly diminished by utilising a protocol of flow-injection analysis (FIA). The method is based on filterless preconcentration of metallic elements at the walls...... of a knotted reactor that was made of nylon tubings. In the load mode, the preconcentration was accomplished by precipitation of metallic species in alkaline-buffered carriers onto the inner walls of the hydrofilic tube. After a preconcen-tration period of 40-120 seconds using sample volumes of 4-10 m......L, the analyte was transferred by a FIAS 400 system to the ICP-MS detector by dissolving the species in an acidic carrier. The magnitude of the enrichment factor largely depended on the time of preconcentration, on the pH-value of the preconcentration buffer and on the pH-value of the samples. Enrichment factors...

  13. Indications of Segmental Flow in Straight Pipes by Flow Injection with Spectrophotometric Detection

    DEFF Research Database (Denmark)

    Andersen, Jens Enevold Thaulov

    2000-01-01

    A procedure of spectrophotometric analysis of fluid flow in pipes is described and its performance is tested on three different dye compounds. The procedure follows measurement and mathematical de-convolution of the signal with an exponential function that is associated with molecular diffusion....... Evidence is provided for the presence of segmental flow and the three dye compounds, used as tracer molecules, indicate that the solute molecules gain velocity, predominantly in the streamwise direction, from the solvent flow rate. The additional velocity, as gained from the solvent flow rate, depends...... on a kinetic-diffusion constant and the internal friction of the system. The model allows a calculation of the flow-injection signal and serves as a tool for the investigation of properties of fluid dynamics....

  14. Amperometric Sensor for Detection of Chloride Ions

    Directory of Open Access Journals (Sweden)

    Rene Kizek

    2008-09-01

    Full Text Available Chloride ion sensing is important in many fields such as clinical diagnosis, environmental monitoring and industrial applications. We have measured chloride ions at a carbon paste electrode (CPE and at a CPE modified with solid AgNO3, a solution of AgNO3 and/or solid silver particles. Detection limits (3 S/N for chloride ions were 100 μM, 100 μM and 10 μM for solid AgNO3, solution of AgNO3 and/or solid silver particles, respectively. The CPE modified with silver particles is the most sensitive to the presence chloride ions. After that we approached to the miniaturization of the whole electrochemical instrument. Measurements were carried out on miniaturized instrument consisting of a potentiostat with dimensions 35 × 166 × 125 mm, screen printed electrodes, a peristaltic pump and a PC with control software. Under the most suitable experimental conditions (Britton-Robinson buffer, pH 1.8 and working electrode potential 550 mV we estimated the limit of detection (3 S/N as 500 nM.

  15. Flow Injection Analysis with Chemiluminescence detection for Determination of Two Phenothiazines

    Directory of Open Access Journals (Sweden)

    Hijran S. Jabbar

    2015-03-01

    Full Text Available A new flow injection analysis-chemiluminescence (FIA-CL method for determination of two phenothiazine derivatives "chlorpromazine hydrochloride (CPZ and promethazine hydrochloride (PTZ" described. The redox reaction between Fe(III and phenothiazines was taken as a base of this new method. A well-defined volume of CPZ or PTZ and luminol solution is injected simultaneously by means of two injection valves in accordance with the merging zone principle. Calibration graphs were constructed in the range of (0.05 – 1.4μg/ml for CPZ with correlation coefficient of (0.9972 and in the range of (0.5 – 40μg/ml for PTZ with correlation coefficient of (0.9978. The precision and accuracy of the method were checked by calculation of relative standard deviation (RSD and relative error percentage (%E for two different levels of concentrations. The method was relatively free from common excipients and it is applied successfully for the determination of CPZ and PTZ in pharmaceutical formulations. The results obtained were in good agreement with those obtained by a reference method in British Pharmacopoeia.

  16. The determination of levofloxacin by flow injection analysis using UV detection, potentiometry, and conductometry in pharmaceutical preparations.

    Science.gov (United States)

    Altiokka, G; Atkosar, Z; Can, N O

    2002-10-15

    A flow injection analysis (FIA) using UV detection, potentiometry and conductometry for levofloxacin (LVF) are described in this study. The best solvent system was found to consist of 0.2 M acetate buffer at pH 3 having 10% MeOH. A flow rate of 1 ml min(-1) was pumped and active material was detected at 288 nm. The detection limit (LOD) and limit of quantification (LOQ) for FIA were calculated to be 3 x 10(-7) M (S/N = 3) and 1 x 10(-7) M (S/N = 10), respectively. In the analysis of tablets, the RSD values were found to be 0.83, 0.98 and 0.99 for FIA, potentiometric and conductometric methods, respectively.

  17. DNA chip based sensor for amperometric detection of infectious pathogens.

    Science.gov (United States)

    Singh, Swati; Kaushal, Ankur; Khare, Shashi; Kumar, Ashok

    2017-10-01

    Several infectious pathogens are found in human whose detection is essential for rapid cure of diseases. The most commonly found pathogen in human is Streptococcus pyogenes which leads to a wide range of infections from mild pharyngitis to rheumatic heart disease. An ultrasensitive DNA chip based sensor was developed for quick identification of pathogen S. pyogenes from patient throat swab samples. The amperometric response was measured after hybridization of specific probe with single stranded genomic DNA (ssG-DNA) from the patient samples. The DNA chip was characterized by FTIR, SEM and validated with suspected patient real samples. The sensitivity of the DNA chip based sensor was found 951.34(μA/cm(2))/ng DNA and lower limit of detection (LOD) was 130fg/6μL samples. The DNA chip based sensor is highly specific and takes only 30min for identification of specific pathogen. Copyright © 2017 Elsevier B.V. All rights reserved.

  18. Micro amperometric immunosensor for the detection of salmonella typhimurium

    Science.gov (United States)

    Sun, Jizhou; Xia, Shanhong; Bian, Chao; Qu, Lan

    2008-12-01

    In this paper, a micro amperometric immunosensor based on Micro-Electro-Mechanical Systems technology for the detection of Salmonella typhimurium (S. typhimurium) was constructed by immobilizing a polyclonal antibody (the bio-molecular recognition element) onto the surface of polypyrrole(PPy) /staphylococcal protein A(SPA) modified Pt electrode. Pyrrole doped with SPA was co-electropolymerized onto the working electrode surface by cyclic voltammetry in 10 minutes for orientation-controlled immobilization of salmonella capture antibodies. S. typhimurium with the concentration of 102cfu/ml could be detected by this immunosensor with a controllable and convenient manipulation to effectively modify the sensing surface more rapidly with less consumption of reagent (10µL), which showed the good property of the sensor. It is potential to develop a micro biosensor that can be used for convenient, accurate, cost-effective and real-time sensing of pathogens in food products.

  19. Evaluation of flow injection analysis method with spectrophotometric detection for the determination of atrazine in soil extracts.

    Science.gov (United States)

    Martins, Elisandra C; Melo, Vander De F; Abate, Gilberto

    2016-09-01

    A method for determining atrazine in soil extracts was evaluated by flow injection analysis with spectrophotometric detection. The method is based on the reaction of atrazine with pyridine in an acid medium followed by the reaction with NaOH and sulfanilic acid. Several analytical conditions were previously studied and optimized. Under the best conditions of analysis, the limits of detection and quantification were 0.15 and 0.45 mg L(-1), respectively, for a linear response between 0.50 and 2.50 mg L(-1), and a sampling throughput of 21 determinations per hour. Using the standard addition method, the maximum relative standard deviation of 17% and recovery values between 80 and 100% were observed for three extracts from soil samples with different composition. The proposed method is simple, low-cost and easy to use, and can be employed for studies involving atrazine in soil samples or for screening of atrazine in soils.

  20. Determination of free and total sulfites in wine using an automatic flow injection analysis system with voltammetric detection.

    Science.gov (United States)

    Goncalves, Luis Moreira; Grosso Pacheco, Joao; Jorge Magalhaes, Paulo; Antonio Rodrigues, Jose; Araujo Barros, Aquiles

    2010-02-01

    An automated flow injection analysis (FIA) system, based on an initial analyte separation by gas-diffusion and subsequent determination by square-wave voltammetry (SWV) in a flow cell, was developed for the determination of total and free sulfur dioxide (SO(2)) in wine. The proposed method was compared with two iodometric methodologies (the Ripper method and a simplified method commonly used by the wine industry). The developed method displayed good repeatability (RSD lower than 6%) and linearity (between 10 and 250 mg l(-1)) as well as a suitable LOD (3 mg l(-1)) and LOQ (9 mg l(-1)). A major advantage of this system is that SO(2) is directly detected by flow SWV.

  1. Analysis of tetracycline antibiotics using HPLC with pulsed amperometric detection.

    Science.gov (United States)

    Charoenraks, Thiraporn; Chuanuwatanakul, Suchada; Honda, Kensuke; Yamaguchi, Yoko; Chailapakul, Orawon

    2005-03-01

    The analysis of tetracycline, oxytetracyline, chlortetracycline and doxycycline by high-performance liquid chromatography with pulsed amperometric detection using an anodized boron-doped diamond thin film (BDD) electrode is originally reported. The analyses were carried out using the mobile phase, phosphate buffer (0.01 M, pH 2.5)-acetonitrile (80:20; v/v), on a C18 column (250 x 4.6 mm i.d., 5 microm) at a flow rate of 1.0 mL/min. The optimal PAD waveform parameters at the anodized BDD were 1.5 V (versus Ag/AgCl) detection potential (E(det)) for 290 ms (200 ms delay time and 90 ms integration time), 2.0 V (versus Ag/AgCl) oxidation potential (E(oxd)) for 200 ms oxidation time (t(oxd)) and 0.4 V (versus Ag/AgCI) reduction potential (E(red)) for 200 ms reduction time (t(red)). The proposed method showed the simultaneous determination of tetracycline, oxytetracyline, chlortetracycline and doxycycline with a linear range of 0.1 - 100 microg/mL, detection limits of 0.05 - 0.1 microg/mL and recoveries of 70.8 - 96.0%. The application of this method to real samples was demonstrated and validated using a shrimp sample.

  2. A micro amperometric immunosensor for detection of human immunoglobulin

    Institute of Scientific and Technical Information of China (English)

    XU Yuanyuan; XIA Shanhong; BIAN Chao; CHEN Shaofeng

    2006-01-01

    A novel amperometric immunosensor based on the micro electromechanical systems (MEMS) technology, using protein A and self-assembled monolayers (SAMs) for the orientation-controlled immobilization of antibodies, has been developed. Using MEMS technology, an "Au, Pt, Pt" three-microelectrode system enclosed in a SU-8 micro pool was fabricated. Employing SAMs, a monolayer of protein A was immobilized on the cysteamine modified Au electrode to achieve the orientation-controlled immobilization of the human immunoglobulin (HIgG) antibody. The immunosensor aimed at low unit cost, small dimension, high level of integration and the prospect of a biosensor system-on-a-chip. Cyclic voltammetry and chronoamperometry were conducted to characterize the immunosensor. Compared with the traditional immunosensor using bulky gold electrode or screen-printed electrode and the procedure directly binding protein A to electrode for immobilization of antibodies, it had attractive advantages, such as miniaturization, compatibility with CMOS technology, fast response (30 s), broad linear range (50-400μg/L) and low detection limit (10μg/L) for HIgG. In addition, this immunosensor was easy to be designed into micro array and to realize the simultaneously multi-parameter detection.

  3. Amperometric screen-printed algal biosensor with flow injection analysis system for detection of environmental toxic compounds

    Energy Technology Data Exchange (ETDEWEB)

    Shitanda, Isao [Department of Pure and Applied Chemistry, Faculty of Science and Technology, Tokyo University of Science, 2641 Yamazaki, Noda, Chiba 278-8510 (Japan)], E-mail: shitanda@rs.noda.tus.ac.jp; Takamatsu, Satoshi; Watanabe, Kunihiro; Itagaki, Masayuki [Department of Pure and Applied Chemistry, Faculty of Science and Technology, Tokyo University of Science, 2641 Yamazaki, Noda, Chiba 278-8510 (Japan)

    2009-08-30

    A screen-printed algal biosensor was fabricated for evaluation of toxicity of chemicals. An algal ink was prepared by mixing unicellular microalga Chlorella vulgaris cells, carbon nanotubes and sodium alginate solution. The algal ink was immobilized directly on a screen-printed carbon electrode surface using screen-printing technique. Photosynthetically generated oxygen of the immobilized algae was monitored amperometically. Responses of the algal biosensor to four toxic compounds, 6-chloro-N-ethyl-N-isopropyl-1,3,5-triazine-2,4-diamine (atrazine) and 3-(3,4-dichlorophenyl)-1,1-diethylurea (DCMU) were evaluated as inhibition ratios of the reduction current. The concentrations that gave 50% inhibition of the oxygen reduction current (IC{sup '}{sub 50}) for atrazine and DCMU were 12 and 1 {mu}mol dm{sup -3}, respectively. In comparison with the conventional algal biosensors, in which the algal cells were entrapped in an alginate gel and immobilized on the surface of a transparent indium tin oxide electrode, the present sensor is much smaller and less expensive, with the shorter assay time.

  4. FLOW INJECTION AMPEROMETRIC DETECTION OF OP NERVE AGENTS BASED ON AN ORGANOPHOSPHORUS-HYDROLASE BIOSENSOR DETECTOR. (R828160)

    Science.gov (United States)

    The perspectives, information and conclusions conveyed in research project abstracts, progress reports, final reports, journal abstracts and journal publications convey the viewpoints of the principal investigator and may not represent the views and policies of ORD and EPA. Concl...

  5. Electrochemical flow injection analysis of hydrazine in an excess of an active pharmaceutical ingredient: achieving pharmaceutical detection limits electrochemically.

    Science.gov (United States)

    Channon, Robert B; Joseph, Maxim B; Bitziou, Eleni; Bristow, Anthony W T; Ray, Andrew D; Macpherson, Julie V

    2015-10-06

    The quantification of genotoxic impurities (GIs) such as hydrazine (HZ) is of critical importance in the pharmaceutical industry in order to uphold drug safety. HZ is a particularly intractable GI and its detection represents a significant technical challenge. Here, we present, for the first time, the use of electrochemical analysis to achieve the required detection limits by the pharmaceutical industry for the detection of HZ in the presence of a large excess of a common active pharmaceutical ingredient (API), acetaminophen (ACM) which itself is redox active, typical of many APIs. A flow injection analysis approach with electrochemical detection (FIA-EC) is utilized, in conjunction with a coplanar boron doped diamond (BDD) microband electrode, insulated in an insulating diamond platform for durability and integrated into a two piece flow cell. In order to separate the electrochemical signature for HZ such that it is not obscured by that of the ACM (present in excess), the BDD electrode is functionalized with Pt nanoparticles (NPs) to significantly shift the half wave potential for HZ oxidation to less positive potentials. Microstereolithography was used to fabricate flow cells with defined hydrodynamics which minimize dispersion of the analyte and optimize detection sensitivity. Importantly, the Pt NPs were shown to be stable under flow, and a limit of detection of 64.5 nM or 0.274 ppm for HZ with respect to the ACM, present in excess, was achieved. This represents the first electrochemical approach which surpasses the required detection limits set by the pharmaceutical industry for HZ detection in the presence of an API and paves the wave for online analysis and application to other GI and API systems.

  6. Detection of Total Phenol in Green and Black Teas by Flow Injection System and Unmodified Screen Printed Electrode

    Directory of Open Access Journals (Sweden)

    Ivanildo Luiz de Mattos

    2010-01-01

    Full Text Available A flow injection system using an unmodified gold screen-printed electrode was employed for total phenol determination in black and green teas. In order to avoid passivation of the electrode surface due to the redox reaction, preoxidation of the sample was realized by hexacyanoferrate(III followed by addition of an EDTA solution. The complex formed in the presence of EDTA minimizes or avoids polymerization of the oxidized phenols. The previously filtered tea sample and hexacyanoferrate(III reagent were introduced simultaneously into two-carrier streams producing two reproducible zones. At confluence point, the pre-oxidation of the phenolic compounds occurs while this zone flows through the coiled reactor and receives the EDTA solution before phenol detection. The consumption of ferricyanide was monitorized at 360 mV versus Ag/AgCl and reflected the total amount of phenolic compounds present in the sample. Results were reported as gallic acid equivalents (GAEs. The proposed system is robust, versatile, environmentally-friendly (since the reactive is used only in the presence of the sample, and allows the analysis of about 35–40 samples per hour with detection limit = 1 mg/L without the necessity for surface cleaning after each measurement. Precise results are in agreement with those obtained by the Folin-Ciocalteu method.

  7. Ultrasensitive detection of streptomycin using flow injection analysis-electrochemical quartz crystal nanobalance (FIA-EQCN) biosensor.

    Science.gov (United States)

    Mishra, Geetesh K; Sharma, Atul; Bhand, Sunil

    2015-05-15

    This work presents the development of an ultrasensitive biosensor for detection of streptomycin residues in milk samples using flow injection analysis-electrochemical quartz crystal nanobalance (FIA-EQCN) technique. Monoclonal antibody specific to streptomycin was immobilized on to the thiol modified gold quartz crystal surface. A broad dynamic range (0.3-300 ng/mL) was obtained for streptomycin with a good linearity in the range 0.3-10 ng/mL for PBS and 0.3-50 ng/mL for milk. The correlation coefficient (R(2)) of the biosensor was found to be 0.994 and 0.997 for PBS and milk respectively. Excellent recoveries were obtained from the streptomycin spiked milk samples in the range 98-99.33%, which shows the applicability of the developed biosensor in milk. The reproducibility of the developed biosensor was found satisfactory with % RSD (n=5) 0.351. A good co-relation was observed between the streptomycin recoveries measured through the developed biosensor and the commercial ELISA kit. The analytical figures of merit of the developed biosensor confirm that the developed FIA-EQCN biosensor could be very effective for low-level detection of streptomycin in milk samples.

  8. Flow Injection Analysis with Electrochemical Detection for Rapid Identification of Platinum-Based Cytostatics and Platinum Chlorides in Water

    Directory of Open Access Journals (Sweden)

    Marketa Kominkova

    2014-02-01

    Full Text Available Platinum-based cytostatics, such as cisplatin, carboplatin or oxaliplatin are widely used agents in the treatment of various types of tumors. Large amounts of these drugs are excreted through the urine of patients into wastewaters in unmetabolised forms. This phenomenon leads to increased amounts of platinum ions in the water environment. The impacts of these pollutants on the water ecosystem are not sufficiently investigated as well as their content in water sources. In order to facilitate the detection of various types of platinum, we have developed a new, rapid, screening flow injection analysis method with electrochemical detection (FIA-ED. Our method, based on monitoring of the changes in electrochemical behavior of analytes, maintained by various pH buffers (Britton-Robinson and phosphate buffer and potential changes (1,000, 1,100 and 1,200 mV offers rapid and cheap selective determination of platinum-based cytostatics and platinum chlorides, which can also be present as contaminants in water environments.

  9. Flow injection analysis with electrochemical detection for rapid identification of platinum-based cytostatics and platinum chlorides in water.

    Science.gov (United States)

    Kominkova, Marketa; Heger, Zbynek; Zitka, Ondrej; Kynicky, Jindrich; Pohanka, Miroslav; Beklova, Miroslava; Adam, Vojtech; Kizek, Rene

    2014-02-04

    Platinum-based cytostatics, such as cisplatin, carboplatin or oxaliplatin are widely used agents in the treatment of various types of tumors. Large amounts of these drugs are excreted through the urine of patients into wastewaters in unmetabolised forms. This phenomenon leads to increased amounts of platinum ions in the water environment. The impacts of these pollutants on the water ecosystem are not sufficiently investigated as well as their content in water sources. In order to facilitate the detection of various types of platinum, we have developed a new, rapid, screening flow injection analysis method with electrochemical detection (FIA-ED). Our method, based on monitoring of the changes in electrochemical behavior of analytes, maintained by various pH buffers (Britton-Robinson and phosphate buffer) and potential changes (1,000, 1,100 and 1,200 mV) offers rapid and cheap selective determination of platinum-based cytostatics and platinum chlorides, which can also be present as contaminants in water environments.

  10. Flow injection analysis of organic peroxide explosives using acid degradation and chemiluminescent detection of released hydrogen peroxide.

    Science.gov (United States)

    Mahbub, Parvez; Zakaria, Philip; Guijt, Rosanne; Macka, Mirek; Dicinoski, Greg; Breadmore, Michael; Nesterenko, Pavel N

    2015-10-01

    The applicability of acid degradation of organic peroxides into hydrogen peroxide in a pneumatically driven flow injection system with chemiluminescence reaction with luminol and Cu(2+) as a catalyst (FIA-CL) was investigated for the fast and sensitive detection of organic peroxide explosives (OPEs). The target OPEs included hexamethylene triperoxide diamine (HMTD), triacetone triperoxide (TATP) and methylethyl ketone peroxide (MEKP). Under optimised conditions maximum degradations of 70% and 54% for TATP and HMTD, respectively were achieved at 162 µL min(-1), and 9% degradation for MEKP at 180 µL min(-1). Flow rates were precisely controlled in this single source pneumatic pressure driven multi-channel FIA system by model experiments on mixing of easily detectable component solutions. The linear range for detection of TATP, HMTD and H2O2 was 1-200 µM (r(2)=0.98-0.99) at both flow rates, while that for MEKP was 20-200 µM (r(2)=0.97) at 180 µL min(-1). The detection limits (LODs) obtained were 0.5 µM for TATP, HMTD and H2O2 and 10 µM for MEKP. The detection times varied from 1.5 to 3 min in this FIA-CL system. Whilst the LOD for H2O2 was comparable with those reported by other investigators, the LODs and analysis times for TATP and HMTD were superior, and significantly, this is the first time the detection of MEKP has been reported by FIA-CL.

  11. On-line Speciation of Cr(III) and Cr(VI) by Flow Injection Analysis With Spectrophotometric Detection and Chemometrics

    DEFF Research Database (Denmark)

    Diacu, Elena; Andersen, Jens Enevold Thaulov

    2003-01-01

    A flow injection system has been developed, for on-line speciation. of Cr(III) and Cr(VI) by the Diphenylcarbazide (DPC) method with H2O2 oxidation followed by spectrophotometric detection at the 550 nm wavelength. The data thus obtained were subjected to a chemometric analysis (PLS), which showe...

  12. Determination of Vitamin B1 in Pharmaceutical Preparations by Flow-injection Analysis with Biamperometric Detection

    Institute of Scientific and Technical Information of China (English)

    LI Li-jun; CHENG Hao; ZHAO Chuan; HU Xiao-ge

    2005-01-01

    A new electrochemical method for the on-line determination of vitamin B1 is presented. Based on dead-stop endpoint biamperometry by using two platinum foil electrodes with an applied potential difference of 150 mV, vitamin B1can be oxidized by hexacyanoferrate ( Ⅲ ) in a sodium hydroxide medium via a reversible indicating couple Fe( CN)64-/Fe(CN)63-. The cell current is linear with the concentration of vitamin B1 in the concentration range of 4.0×10-6-1.0 × 10-3 mol/L with a detection limit of 8.0×10-7 mol/L(0. 27 μg/mL). Most familiar excipients,ions and vitamins do not interfere with the determination of vitamin B1. The method displays the advantages of simplicity, high efficiency( 180 samples/h), and high selectivity, and is suitable for the determination of vitamin B1 in pharmaceutical preparations.

  13. Determination of nabumetone in pharmaceutical formulation by flow injection analysis (FIA) with UV-detection.

    Science.gov (United States)

    Can, N O; Tuncel, M; Aboul-Enein, H Y

    2003-01-01

    A precise and accurate FIA method for the quantification of nabumetone (NAB) in pharmaceuticals is described. The best suitable carrier solvent system consisted of ethanol: water (30:70 v/v). Sample solution (4.7 x 10(-6) M NAB) was prepared in this solvent and injected to the instrumental system at a flow rate of 1.2 ml x min(-1). The signals were detected by a UV detector at 228.8 nm. The calibration curves of NAB was linear in the concentration range of 1.4 x 10(-6) M-2.8 x 10(-5) M. The intra- and inter-assay precision were less than 2.6%. The method exhibited a good linearity with the correlation coefficients. The LOD and LOQ values were found to be 4.4 x 10(-7) and 1.3 x 10(-6) M, respectively. The effects of the tablet excipients were insignificant at the 95% probability level. The calculated tablet content was 99% which is agreement with the ranges stated by pharmacopoeias.

  14. Flow injection with in-line reduction column and conductometric detection for determination of total inorganic nitrogen in soil.

    Science.gov (United States)

    Yanu, Pattama; Jakmunee, Jaroon

    2015-11-01

    A cost effective flow injection (FI) conductometric system has been developed for determination of total inorganic nitrogen (TIN). The system is aimed for evaluation of nitrogen nutrient in soil for agricultural application. Inorganic nitrogen compounds were extracted from soil according to the standard method by using potassium chloride solution as an extractant, and the extracted solution was then injected into the FI system. Nitrate and nitrite are converted to ammonium ion by an in-line reduction column packed with a Devarda's alloy. A gas diffusion unit was incorporated into the FI system to separate ammonium ion from other ions in a donor stream by forming ammonia gas that can diffuse through a PTFE membrane to re-dissolve in an acceptor stream. Conductance of the acceptor stream was directly proportional to ammonium ion concentration. Various parameters affecting reduction efficiency of the column, e.g., column diameter, column packing procedure, and column length was investigated and optimized. A linear calibration graph in the range of 2.00-60.00 mg L(-1) N-NH4(+) (y=0.123x+0.039, R(2) =0.997) was obtained with a limit of detection of 0.47 mg L(-1). Sample throughput of 20 samples h(-1) was achieved. The result of developed method was correlated with total Kjeldahl nitrogen (TKN) obtained from the Kjeldahl digestion method. The proposed method could be used as an alternative method to the Kjeldahl method for determination of TIN in soil.

  15. Analysis of total polyphenols in wines by FIA with highly stable amperometric detection using carbon nanotube-modified electrodes.

    Science.gov (United States)

    Arribas, Alberto Sánchez; Martínez-Fernández, Marta; Moreno, Mónica; Bermejo, Esperanza; Zapardiel, Antonio; Chicharro, Manuel

    2013-02-15

    The use of glassy carbon electrodes (GCEs) modified with multi-walled carbon nanotube (CNT) films for the continuous monitoring of polyphenols in flow systems has been examined. The performance of these modified electrodes was evaluated and compared to bare GCE by cyclic voltammetry experiments and by flow injection analysis (FIA) with amperometric detection monitoring the response of gallic, caffeic, ferulic and p-coumaric acids in 0.050 M acetate buffer pH 4.5 containing 100 mM NaCl. The GCE modified with CNT dispersions in polyethyleneimine (PEI) provided lower overpotentials, higher sensitivity and much higher signal stability under a dynamic regime than bare GCEs. These properties allowed the estimation of the total polyphenol content in red and white wines with a remarkable long-term stability in the measurements despite the presence of potential fouling substances in the wine matrix. In addition, the versatility of the electrochemical methodology allowed the selective estimation of the easily oxidisable polyphenol fraction as well as the total polyphenol content just by tuning the detection potential at +0.30 or 0.70 V, respectively. The significance of the electrochemical results was demonstrated through correlation studies with the results obtained with conventional spectrophotometric assays for polyphenols (Folin-Ciocalteu, absorbance at 280 nm index and colour intensity index). Copyright © 2012 Elsevier Ltd. All rights reserved.

  16. Determination of Free and Total Sulfites in Wine using an Automatic Flow Injection Analysis System with Voltammetric Detection

    OpenAIRE

    Gonçalves, Luís Moreira; Pacheco, João Grosso; Magalhães, Paulo Jorge; Rodrigues, José António; Barros, Aquiles Araújo

    2009-01-01

    Abstract An automated Flow Injection Analysis (FIA) system based on a initial analyte separation by gas-diffusion and subsequent determination by square-wave voltammetry (SWV) in a flow cell is proposed for the determination of total and free content of sulphur dioxide (SO2) in wine. The proposed method was compared with two iodometric methodologies (the Ripper method and the simplified method commonly used by the wine industry). The developed method shown repeatability (RSD lower ...

  17. Mathematical modelling of a single-line flow-injection analysis systems with single-layer enzyme electrode detection. Pt. 3; Experimental verification of the model

    Energy Technology Data Exchange (ETDEWEB)

    Kolev, S.D. (Sofia Univ. (Bulgaria). Khimicheski Fakultet); Nagy, Geza; Pungor, Ernoe (Budapesti Mueszaki Egyetem, Budapest (Hungary). Altalanos es Analitikai Kemia Tanszek)

    1991-11-20

    Glucose and urea electrodes, prepared by two different enzyme immobilization techniques and used as detectors in a single-line flow-injection manifold, were experimentally investigated for elucidating the influence of their most important parameters, i.e., the initial substrate concentration in the sample, the enzyme concentration in the reaction layer and its thickness and the buffer concentration, on the output signal. The results obtained were compared with the theoretical predictions based on simulations of the model for single-line flow-injection systems with single-layer enzyme electrode detection. The good qualitative agreement which was observed is a convincing experimental verification of this model and the guidelines for the production of flow-through biocatalytic electrodes with optimum design based upon it. (author). 12 refs.; 6 figs.

  18. Construction and evaluation of a novel end-column amperometric detection system for electrophoresis microchips

    Institute of Scientific and Technical Information of China (English)

    2010-01-01

    A set of integrated end-column amperometric detection system has been developed,onto which an electrophoresis microchip can be conveniently integrated.Finely machined by a piece of transparent organic glass,the system consists of an electrophoresis microchip platform and an amperometric detection reservoir,in which the microchip can be fixed onto the platform by microchip grooves and with stainless steel fixture.Each detection electrode can be directly fixed in the amperometric detection reservoir by screws and nuts.With dopamine as the model analyte,we take platinum disc electrodes with different diameters of 100 μm,300 μm and 500 μm and a carbon fiber electrode with the diameter of 240 μm as the working electrode,all of which accomplish sensitive detection.The detection parameters of the system are optimized with the carbon fiber electrode.The detection results show that in the electrochemical cleaning procedure,the relative deviations of 3.2% and 0.5% for the peak current and retention time,respectively,can be obtained for the successive detections of 100 μM dopamine,and the limit of detection for dopamine can reach 0.4 μM(S/N = 3).This system is small,but its performance of detection is stable and sensitive,and the replacement of its working electrodes is convenient,so it is very suitable as a universal platform of end-column amperometric detection for electrophoresis microchips.

  19. The interference of HEPES buffer during amperometric detection of ATP in clinical applications.

    Science.gov (United States)

    Masson, Jean-Francois; Gauda, Estelle; Mizaikoff, Boris; Kranz, Christine

    2008-04-01

    HEPES-based biological buffer is subject to photooxidation upon exposure to fluorescent illumination. Thereby hydrogen peroxide is generated, which interferes with amperometric oxidoreductase-based biosensors for glucose or adenosine triphosphate (ATP). These biosensors operate at an oxidation potential above 500 mV vs. the standard calomel electrode (SCE) and involve hydrogen peroxide as the electroactive molecule detected at the electrode surface. False-positive detection of ATP was observed in HEPES buffer utilizing an amperometric microbiosensor based on the co-immobilization of glucose oxidase and hexokinase for detection of ATP in biological specimens. Electrochemical, mass spectrometric, (31)P NMR, and (1)H NMR studies indicate that complexation of ATP and HEPES induced by the presence of Ca(2+) in HEPES buffer decreases the photooxidation of HEPES. Consequently, the hydrogen peroxide background concentration is reduced, thereby leading to erroneous ATP detection at the dual-enzyme microbiosensor, which determines an increase in ATP via a reduced hydrogen peroxide signal.

  20. Flow injection on-line preconcentration of low levels of Cr(VI) with detection by ETAAS

    DEFF Research Database (Denmark)

    Som-aum, Waraporn; Liawruangrath, Saisunee; Hansen, Elo Harald

    2002-01-01

    A flow injection (FI) on-line sorption preconcentration procedure utilizing a packed column reactor and combined with electrothermal atomic absorption spectrometry (ETAAS) is proposed for the determination of low levels of Cr(VI) in water samples. Polytetrafluoroethylene (PTFE) beads packed...... in a mini-column is used as sorbent material. The complex formed between Cr(VI) and ammonium pyrrolidine dithiocarbamate (APDC) is sorbed on the PTFE beads, and is subsequently eluted by an air-monosegmented discrete zone of absolute ethanol (35mul), the analyte being quantified by ETAAS....... The preconcentration procedure using the proposed column significantly enhances the preconcentration efficiency as compared with the preconcentration approach incorporating an open tubular PTFE knotted reactor (KR). Comparing the two procedure for equal surface sorption area, the advantages of using a packed column...

  1. Second-order Data by Flow Injection Analysis with Spectrophotometric Diode-array Detection and Incorporated Gel-filtration Chromatographic Column

    DEFF Research Database (Denmark)

    Bechmann, Iben Ellegaard

    1997-01-01

    A flow injection analysis (FIA) system furnished with a gel-filtration chromatographic column and with photodiode-array detection was used for the generation of second-order data. The system presented is a model system in which the analytes are blue dextran, potassium hexacyanoferrate......(III) and heparin. It is shown that the rank of the involved sample data matrices corresponds to the number of chemical components present in the sample. The PARAFAC (parallel factor analysis) algorithm combined with multiple linear regression and the tri-PLS (tri-linear partial least-squares regression), which...

  2. Amperometric Detection of Bacillus anthracis Spores: A Portable, Low-Cost Approach to the ELISA

    Directory of Open Access Journals (Sweden)

    Gabriel D. Peckham

    2013-01-01

    Full Text Available Antibody-based detection assays are generally robust, a desirable characteristic for in-the-field use. However, to quantify the colorimetric or fluorescent signal, these assays require expensive and fragile instruments which are ill-suited to in-the-field use. Lateral flow devices (LFDs circumvent these barriers to portability but suffer from poor sensitivity and subjective interpretation. Here, an antibody-based method for detecting Bacillus anthracis spores via amperometric signal generation is compared to ELISA and LFDs. This amperometric immunoassay uses antibody conjugated to magnetic beads and glucose oxidase (GOX along with the electron mediator 2, 6-dichlorophenolindophenol (DCPIP for production of a measurable current from a 0.4 V bias voltage. With similar sensitivity to ELISA, the assay can be completed in about 75 minutes while being completely powered and operated from a laptop computer. Immunoassay amperometry holds promise for bringing low-cost, quantitative detection of hazardous agents to the field.

  3. Determination of catecholamines in plasma by HPLC and amperometric detection. Comparison with a radioenzymatic method.

    Science.gov (United States)

    Bauersfeld, W; Ratge, D; Knoll, E; Wisser, H

    1986-03-01

    The determination of norepinephrine and epinephrine in plasma by HPLC with amperometric detection was modified, giving detection limits of 25 ng/l for norepinephrine and epinephrine, respectively, using 1 ml plasma. In order to achieve this sensitivity, it was necessary to minimize the background noise by modification of instrumentation and specimen handling. Particularly important was the extra purification of the reagents, the application of micro-bore HPLC, the enzymatic cleavage of uric acid and temperature control of the amperometric cell and the amplifier. Comparison of the present method with the radioenzymatic determination of catecholamines resulted in coefficients of correlation of r = 0.924 and 0.919 for norepinephrine and epinephrine, resp. (n = 38). The concentrations of the 38 different samples used for the comparison were in the physiological range.

  4. AN APPLICATION OF FLOW INJECTION ANALYSIS WITH GAS DIFFUSION AND SPECTROPHOTOMETRIC DETECTION FOR THE MONITORING OF DISSOLVED SULPHIDE CONCENTRATION IN ENVIRONMENTAL SAMPLES

    Directory of Open Access Journals (Sweden)

    Malwina Cykowska

    2014-10-01

    Full Text Available The monitoring of the concentration of sulphide is very important from the environment point of view because of high toxicity of hydrogen sulphide. What is more hydrogen sulphide is an important pollution indicator. In many cases the determination of sulphide is very difficult due to complicated matrix of some environmental samples, which causes that most analytical methods cannot be used. Flow injection analysis allows to avoid matrix problem what makes it suitable for a wide range of applications in analytical laboratories. In this paper determination of dissolved sulphide in environmental samples by gas-diffusion flow injection analysis with spectrophotometric detection was presented. Used gas-diffusion separation ensures the elimination of interferences caused by sample matrix and gives the ability of determination of sulphides in coloured and turbid samples. Studies to optimize the measurement conditions and to determine the value of the validation parameters (e.g. limit of detection, limit of quantification, precision, accuracy were carried out. Obtained results confirm the usefulness of the method for monitoring the concentration of dissolved sulphides in water and waste water. Full automation and work in a closed system greatly reduces time of analysis, minimizes consumption of sample and reagents and increases safety of analyst’s work.

  5. A Fully Automated Sequential-Injection Analyser for Dual Electrogenerated Chemiluminescence/Amperometric Detection

    OpenAIRE

    Economou, Anastasios; Nika, Maria

    2006-01-01

    This work describes the development of a dedicated, fully automated sequential-injection analysis (SIA) apparatus suitable for simultaneous electrogenerated chemiluminescence (ECL) and amperometric detection. The instrument is composed of a peristaltic pump, a multiposition selection valve, a home-made potentiostat, a thin-layer electrochemical/optical flow-through cell, and a light detector. Control of the experimental sequence and simultaneous data acquisition of the light and the current i...

  6. Electroanalysis of tetracycline using nickel-implanted boron-doped diamond thin film electrode applied to flow injection system.

    Science.gov (United States)

    Treetepvijit, Surudee; Chuanuwatanakul, Suchada; Einaga, Yasuaki; Sato, Rika; Chailapakult, Orawon

    2005-05-01

    The electrochemical analysis of tetracycline was investigated using nickel-implanted boron-doped diamond thin film electrode by cyclic voltammetry and amperometry with a flow injection system. Cyclic voltammetry was used to study the electrochemical oxidation of tetracycline. Comparison experiments were carried out using as-deposited boron-doped diamond thin film electrode (BDD). Nickel-implanted boron-doped diamond thin film electrode (Ni-DIA) provided well-resolved oxidation irreversible cyclic voltammograms. The current signals were higher than those obtained using the as-deposited BDD electrode. Results using nickel-implanted boron-doped diamond thin film electrode in flow injection system coupled with amperometric detection are presented. The optimum potential for tetracycline was 1.55 V versus Ag/AgCl. The linear range of 1.0 to 100 microM and the detection limit of 10 nM were obtained. In addition, the application for drug formulation was also investigated.

  7. Determination of 2-propanol in surface cleaning solutions used for copper continuous casting process by flow injection-spectrophotometric detection with on-line column separation.

    Science.gov (United States)

    Hayashibe, Yutaka; Tokuda, Masahiro; Takeya, Minoru

    2003-09-01

    A flow-injection system has been developed for the determination of 2-propanol in the surface cleaning solutions used in the copper continuous cast rod making system. Adsorption chromatography in nitric acid medium was used for the on-line separation of oily substances in the sample solution. Cerium(IV) diammonium nitrate was utilized as the chromogenic reagent for the spectrophotometric detection of 2-propanol. The system permits a throughput of one sample per hour for the oily sample, and of 12 samples per hour for the none-oily sample. The reproducibility has been proven to be satisfactory with a relative standard deviation of less than 6.0% (2.2%(V/V) 2-propanol level, n = 23). The detection limit is 0.01% (V/V).

  8. Flow injection on-line dilution for multi-element determination in human urine with detection by inductively coupled plasma mass spectrometry

    DEFF Research Database (Denmark)

    Wang, J.H.; Hansen, E.H.; Gammelgaard, Bente

    2001-01-01

    A simple flow injection on-line dilution procedure with detection by inductively coupled plasma mass spectrometry (ICP-MS) was developed for the determination of copper, zinc, arsenic, lead, selenium, nickel and molybdenum in human urine. Matrix effects were minimized by employing a dilution fact...... of 16.5 with on-line standard addition, and Rh-103 was used as internal standard to compensate for signal fluctuation. The procedure was validated by the analysis of two standard reference materials SRM 2670 (NIST) and Seronorm (TM) Trace Elements in Urine. Recovery experiments were pet...... human urine samples. No correlations between the concentrations of the elements were observed. (C) 2001 Elsevier Science B.V. All rights reserved...

  9. Amperometric detection in the presence of carbon nanotubes dispersed in background electrolyte: Evaluating its suitability for capillary electrokinetic chromatography separations of polyphenolic compounds.

    Science.gov (United States)

    Moreno, Mónica; Sánchez Arribas, Alberto; Bermejo, Esperanza; Zapardiel, Antonio; Chicharro, Manuel

    2015-08-01

    This work reports on the positive effects observed upon both the separation and analytical signals in electrophoretic separations of selected phenolic compounds when using aqueous BGE containing carbon nanotubes (CNTs) in connection to electrochemical detection (ECD). The influence of the presence of surfactant-coated CNTs in the BGE upon the amperometric response of probe compounds was evaluated under hydrodynamic regime in capillary flow injection experiments as well as electrophoretic separations. Among the surfactants employed to disperse CNTs within BGE, SDS shows the best results in terms of dispersion stability and degree of dispersion of the CNTs. ECD allows working with BGEs containing CNTs concentrations of, at least, 24.0 mg/L without increasing of baseline noise, on the opposite to that reported when using UV-visible detection, and the presence of CNTs in the BGE improves the electrochemical response of some of the tested compounds. These benefits were reflected in higher sensibility in the electrochemical signal and additional improved resolution in the electrophoretic separation of (±)-catechin and sinapic acid when using these BGE containing CNTs. © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  10. Flow Injection Analysis

    DEFF Research Database (Denmark)

    Hansen, Elo Harald

    2004-01-01

    This chapter provides an introduction to automated chemical analysis, which essentially can be divided into two groups: batch assays, where the solution is stationary while the container is moved through a number of stations where various unit operations performed; and continuous-flow procedures,......, but it permits thr execution of novel and unique analytical procedures which are difficult or even impossible by conventional means. The performance and applicability of FIA, SI and LOV are illustrated by a series of practical examples.......This chapter provides an introduction to automated chemical analysis, which essentially can be divided into two groups: batch assays, where the solution is stationary while the container is moved through a number of stations where various unit operations performed; and continuous-flow procedures......, where the system is stationary while the solution moves through a set of conduits in which all required manipulations are performed. Emphasis is placed on flow injection analysis (FIA) and its further developments, that is, sequential injection analysis (SIA) and the Lab-on-Valve (LOV) approach. Since...

  11. Separation of natural antioxidants using PDMS electrophoresis microchips coupled with amperometric detection and reverse polarity.

    Science.gov (United States)

    Lucca, Bruno Gabriel; Lunte, Susan Marie; Tomazelli Coltro, Wendell Karlos; Ferreira, Valdir Souza

    2014-12-01

    This report describes the use of PDMS ME coupled with amperometric detection for rapid separation of ascorbic, gallic , ferulic, p-coumaric acids using reverse polarity. ME devices were fabricated in PDMS by soft lithography and detection was accomplished using an integrated carbon fiber working electrode aligned in the end-channel configuration. Separation and detection parameters were investigated and the best conditions were obtained using a run buffer consisting of 5 mM phosphate buffer (pH 6.9) and a detection voltage of 1.0 V versus Ag/AgCl reference electrode. All compounds were separated within 70 s using gated injection mode with baseline resolution and separation efficiencies between 1200 and 9000 plates. Calibration curves exhibited good linearity and the LODs achieved ranged from 1.7 to 9.7 μM. The precision for migration time and peak height provided maximum values of 4% for the intrachip studies. Lastly, the analytical method was successfully applied for the analysis of ascorbic and gallic acids in commercial beverage samples. The results achieved using ME coupled with amperometric detection were in good agreement with the values provided by the supplier. Based on the data reported here, the proposed method shows suitability to be applied for the routine analysis of beverage samples.

  12. Studies of Active Ingredients in Cough Syrup by Capillary Zone Electrophoresis with Amperometric Detection

    Institute of Scientific and Technical Information of China (English)

    ZHOU Tian-shu; WANG Ai-fang; WU Fang; SHI Guo-yue; FANG Yu-zhi

    2003-01-01

    The present paper covers a simple, reliable and reproducible method, based on capillary zone electrophoresis(CZE) with amperometric detection(AD), for the separation and the determination of ephedrine hydrochloride, promethazine hydrochloride and codeine phosphate. Under the optimal conditions, the three analytes were base-line separated completely within 16 min. Good linear relationships between the peak heights and the concentrations of the three analytes were obtained with the correlation coefficients better than 0.9993. The method was directly applied to the determination of the active ingredients in pharmaceutical preparations and the assay results were satisfactory.

  13. Study on Rhizoma Chuanxiong based on capillary electrophoresis with amperometric detection

    Institute of Scientific and Technical Information of China (English)

    2010-01-01

    A high-performance capillary electrophoresis with amperometric detection(CE-AD) method has been developed for the analysis of seven bioactive ingredients,namely ferulic acid(FA),vanillin,vanillic acid,p-hydroxybenzoic acid,caffeic acid,gallic acid and protocatechuic acid,in Rhizoma Chuanxiong.The effects of several factors such as the acidity and concentration of running buffer,the separation voltage,the applied potential to working electrode and the injection time were investigated.Under the optimum con...

  14. Disposable amperometric biosensor based on nanostructured bacteriophages for glucose detection

    Science.gov (United States)

    Kang, Yu Ri; Hwang, Kyung Hoon; Kim, Ju Hwan; Nam, Chang Hoon; Kim, Soo Won

    2010-10-01

    The selection of electrode material profoundly influences biosensor science and engineering, as it heavily influences biosensor sensitivity. Here we propose a novel electrochemical detection method using a working electrode consisting of bio-nanowires from genetically modified filamentous phages and nanoparticles. fd-tet p8MMM filamentous phages displaying a three-methionine (MMM) peptide on the major coat protein pVIII (designated p8MMM phages) were immobilized on the active area of an electrochemical sensor through physical adsorption and chemical bonding. Bio-nanowires composed of p8MMM phages and silver nanoparticles facilitated sensitive, rapid and selective detection of particular molecules. We explored whether the composite electrode with bio-nanowires was an effective platform to detect the glucose oxidase. The current response of the bio-nanowire sensor was high at various glucose concentrations (0.1 µm-0.1 mM). This method provides a considerable advantage to demonstrate analyte detection over low concentration ranges. Especially, phage-enabled bio-nanowires can serve as receptors with high affinity and specificity for the detection of particular biomolecules and provide a convenient platform for designing site-directed multifunctional scaffolds based on bacteriophages and may serve as a simple method for label-free detection.

  15. Rapid amperometric detection of trace metals by inhibition of an ultrathin polypyrrole-based glucose biosensor.

    Science.gov (United States)

    Ayenimo, Joseph G; Adeloju, Samuel B

    2016-02-01

    A sensitive and reliable inhibitive amperometric glucose biosensor is described for rapid trace metal determination. The biosensor utilises a conductive ultrathin (55 nm thick) polypyrrole (PPy) film for entrapment of glucose oxidase (GOx) to permit rapid inhibition of GOx activity in the ultrathin film upon exposure to trace metals, resulting in reduced glucose amperometric response. The biosensor demonstrates a relatively fast response time of 20s and does not require incubation. Furthermore, a complete recovery of GOx activity in the ultrathin PPy-GOx biosensor is quickly achieved by washing in 2mM EDTA for only 10s. The minimum detectable concentrations achieved with the biosensor for Hg(2+), Cu(2+), Pb(2+) and Cd(2+) by inhibitive amperometric detection are 0.48, 1.5, 1.6 and 4.0 µM, respectively. Also, suitable linear concentration ranges were achieved from 0.48-3.3 µM for Hg(2+), 1.5-10 µM for Cu(2+), 1.6-7.7 µM for Pb(2+) and 4-26 µM for Cd(2+). The use of Dixon and Cornish-Bowden plots revealed that the suppressive effects observed with Hg(2+) and Cu(2+) were via non-competitive inhibition, while those of Pb(2+) and Cd(2+) were due to mixed and competitive inhibition. The stronger inhibition exhibited by the trace metals on GOx activity in the ultrathin PPy-GOx film was also confirmed by the low inhibition constant obtained from this analysis. The biosensor was successfully applied to the determination of trace metals in tap water samples.

  16. Screening and confirmatory methods for the analysis of macrocyclic lactone mycotoxins by CE with amperometric detection.

    Science.gov (United States)

    Arribas, Alberto Sánchez; Bermejo, Esperanza; Zapardiel, Antonio; Téllez, Helena; Rodríguez-Flores, Juana; Zougagh, Mohammed; Ríos, Angel; Chicharro, Manuel

    2009-02-01

    A simple analytical scheme for the screening and quantification of zearalenone and its metabolites, alpha-zearalenol and beta-zearalenol, is reported. Extracts from maize flour samples were collected by supercritical fluid extraction and afterwards, they were analyzed by CE with amperometric detection. This scheme allowed a rapid and reliable identification of contaminated flour samples according to the reference value established for zearalenone by directive 2005/38/EC (200 microg/kg). The sample screening method was carried out by CZE using 25 mM borate separation buffer at pH 9.2 and 25.0 kV as separation voltage, monitoring the amperometric signal at +700 mV with a carbon paste electrode. In this way, total amount of mycotoxins was determined and samples were processed in 4 min with a detection limit of 12 microg/L, enough to discriminate between positive (more than 200 microg/L total mycotoxins) and negative samples (less than 200 microg/L total mycotoxins). Positive samples were then subjected to CZE separation and quantification of each analyte was done with 50 mM borate running buffer modified with 30% methanol at pH 9.7 and 17.5 kV as separation voltage. Under these conditions, separation was achieved in 15 min with detection limits from 20 to 35 microg/L for each analyte.

  17. Separation and determination of alditols and sugars by high-pH anion-exchange chromatography with pulsed amperometric detection

    DEFF Research Database (Denmark)

    Andersen, Rikke; Sørensen, A.

    2000-01-01

    Carbohydrates such as alditols (polyols or sugar alcohols), monosaccharides and disaccharides are separated as anions by anion-exchange chromatography with a sodium hydroxide eluent, MA1 CarboPac column and pulsed amperometric detection. We report a high-pH anion-exchange chromatographic......-pulsed amperometric detection (HPAEC-PAD) method that determines all the polyols used as food additives in food products and the most commonly found mono- and disaccharides on a routine basis. The linearity, repeatability, internal reproducibility and accuracy are described. The applicability of the method has been...

  18. Determination of neomycin in water samples by high performance anion chromatography with pulsed amperometric detection

    Institute of Scientific and Technical Information of China (English)

    Bin Guan; Dong Xing Yuan

    2007-01-01

    A simple, fast and reliable method, using high performance anion chromatography with pulsed amperometric detection, had been developed for the analysis of neomycin in water samples. The elution and separation were carried out with an isocratic mobile phase, containing 10 mmol/L NaOH. The influence of the concentration and pH of the mobile phase on the separation and detection was investigated. A quadruple-potential waveform used for the detection was optimized. The detection limit of neomycin was down to 0.027 μg/mL. The linearity of neomycin calibration curve ranged from 0.050 to 0.505 μg/mL with correlation coefficient of0.9997. R.S.D. (n= 11) was 4.0%.

  19. A CMOS detection chip for amperometric sensors with chopper stabilized incremental ΔΣ ADC

    Science.gov (United States)

    Min, Chen; Yuntao, Liu; Jingbo, Xiao; Jie, Chen

    2016-06-01

    This paper presents a low noise complimentary metal-oxide-semiconductor (CMOS) detection chip for amperometric electrochemical sensors. In order to effectively remove the input offset of the cascaded integrators and the low frequency noise in the modulator, a novel offset cancellation chopping scheme was proposed in the Incremental ΔΣ analog to digital converter (IADC). A novel low power potentiostat was employed in this chip to provide the biasing voltage for the sensor while mirroring the sensor current out for detection. The chip communicates with FPGA through standard built in I2C interface and SPI bus. Fabricated in 0.18-μm CMOS process, this chip detects current signal with high accuracy and high linearity. A prototype microsystem was produced to verify the detection chip performance with current input as well as micro-sensors. Project supported by the State Key Development Program for Basic Research of China (No. 2015CB352100).

  20. Comparison between amperometric and true potentiometric end-point detection in the determination of water by the Karl Fischer method.

    Science.gov (United States)

    Cedergren, A

    1974-06-01

    A rapid and sensitive method using true potentiometric end-point detection has been developed and compared with the conventional amperometric method for Karl Fischer determination of water. The effect of the sulphur dioxide concentration on the shape of the titration curve is shown. By using kinetic data it was possible to calculate the course of titrations and make comparisons with those found experimentally. The results prove that the main reaction is the slow step, both in the amperometric and the potentiometric method. Results obtained in the standardization of the Karl Fischer reagent showed that the potentiometric method, including titration to a preselected potential, gave a standard deviation of 0.001(1) mg of water per ml, the amperometric method using extrapolation 0.002(4) mg of water per ml and the amperometric titration to a pre-selected diffusion current 0.004(7) mg of water per ml. Theories and results dealing with dilution effects are presented. The time of analysis was 1-1.5 min for the potentiometric and 4-5 min for the amperometric method using extrapolation.

  1. Flow injection spectrophotometric determination of vitamin E in Pharmaceuticals, milk powder and blood serum using potassium ferricyanide-Fe(Ⅲ) detection system

    Institute of Scientific and Technical Information of China (English)

    Saima

    2010-01-01

    A simple and sensitive flow injection spectrophotometric method is reported for the determination of vitamin E using potassium ferricyanide-Fe(Ⅲ detection system. In the presence of vitamin E, Fe(Ⅲ/ferricyanide reduces. The in situ reduced ions are then reacted with unreduced portion of ferricyanide/Fe(Ⅲ to make soluble Prussian blue, which is monitored at absorption wavelength of 735 nm. Linear calibration graph was obtained in the concentration range of 0.1-40 μg mL-1. The relative standard deviations (n = 4) were in the range of 1.1-3.6%, with limits of detection (3 s blank) of 0.04 μg mL-1. The proposed method allowed 12 injections h-1. The method is applied to determine vitamin E in Pharmaceuticals, infant milk and blood serum samples using hexane extraction with the recoveries in the range of 93 ± 3 to 97.5 ± 4%. The method is validated using certified reference materials SRM 968c for blood serum samples.

  2. Determination of phenols by flow injection and liquid chromatography with on-line quinine-sensitized photo-oxidation and quenched luminol chemiluminescence detection

    Energy Technology Data Exchange (ETDEWEB)

    Zhang Wei; Danielson, Neil D

    2003-10-01

    An on-line quinine-sensitized photo-oxidation with quenched chemiluminescence (CL) detection method is developed for phenols using flow injection (FI) and liquid chromatography (LC). This detection method is based on the decrease of light emission from the luminol CL reaction due to the photo-oxidation of phenols that scavenge the photogenerated reactive oxygen species (e.g. singlet oxygen ({sup 1}O{sub 2}) and superoxide (O{sub 2}{center_dot}{sup -})). On-line photo-oxidation is achieved using a coil photo-reactor made from fluoroethylene-propylene copolymer tubing (3048 mmx0.25 mm i.d.) coiled around a mercury UV lamp. A buffer of pH 7 and a concentration of 350 {mu}M for quinine sulfate are determined optimum for the sensitized photo-oxidation. Using a carrier system flow rate of 60 {mu}l/min, calibration curves taken by FI for 10 phenolic compounds in aqueous solutions showed this decreasing sensitivity order: 4-chlorophenol, phenol, 4-nitrophenol, 3-hydroxy-L-kynurenine, 2-nitrophenol, salicylate, 3-nitrophenol, catechol, 2,4-dinitrophenol, and 2,4-dichlorophenol. This detection method using two tandem coil photo-reactors is also applied for the LC separation of phenol, 4-nitrophenol and 4-chlorophenol on an octadecyl (C18) silica LC column using acetonitrile-H{sub 2}O (40:60, v/v) as a mobile phase. The quenched CL detection limits (about 1 {mu}M or 20 pmol) for phenol and 4-chlorophenol are comparable to those for UV detection at 254 nm. Some selectivity in the quenched CL detection is evident by no interference in the FI phenol response even when benzaldehyde and phenethanol concentrations are 8 and 15 times that of phenol.

  3. Characterization of Hg(II) binding with different length phytochelatins using liquid chromatography and amperometric detection.

    Science.gov (United States)

    Dago, Angela; González-García, Olga; Ariño, Cristina; Díaz-Cruz, José Manuel; Esteban, Miquel

    2011-06-10

    A simple and rapid methodology is optimised to analyse mixtures of different phytochelatins (PC(n), n=2-5) with Hg(II) by HPLC with amperometric detection as a first step towards the analysis of extracts of plants stressed with Hg(II). The separation was achieved in a C(18) column with a mobile phase of 0.1% trifluoroacetic acid (TFA) in water and 0.1% TFA in acetonitrile using gradient elution. Electrochemical detection with glassy carbon electrode and UV-vis detection were used in series. This methodology can clearly distinguish between the free peptides and their complexes and permits to study the evolution of the different complexes formed and predicts the possible interactions between the long chain phytochelatin complexes. ESI-MS is used as a complementary technique to find out the stoichiometries of such long chain phytochelatin complexes.

  4. Determination of Roxithromycin Tablets by Capillary Electrophoresis Employing Non-aqueous Media with Square-wave Amperometric Detection

    Institute of Scientific and Technical Information of China (English)

    2002-01-01

    A new method of determination for roxithromycin tablets by non-aqueous capillary electrophoresis (NACE) with square-wave amperometric detection was carried out. Several parameters affecting the NACE-AD determination were studied. The data was modified by spline wavelet least square (SWLS). The method is simple, rapid and highly reliable for routine analysis.

  5. Rapid measurement of free cyanide in liquor by ion chromatography with pulsed amperometric detection.

    Science.gov (United States)

    Wu, Wenlin; Xiao, Quanwei; Zhang, Ping; Ye, Mei; Wan, Yuping; Liang, Hengxing

    2015-04-01

    This study investigated the measurement of free cyanide in liquor by ion chromatography coupled with pulsed amperometric detection (IC-PAD). Eluent concentration, interferent evaluation and method performance were discussed. Results show that free cyanide in liquor can be rapidly determined by the optimised IC-PAD method. A sample requires only 1:100 dilution and simple filtration before being subjected to IC-PAD. The linear range is 1-5000 μg/L with an R value of 0.9998. The detection limit is 1 μg/L for a 25 μL injection loop. The overall relative standard deviation (RSD) of the method is less than 5%, and the recovery range is from 98.1% to 105.0%. This study has been proven significant and may have potential applications in liquors analysis.

  6. DIFFERENTIATION OF AURANTII FRUCTUS IMMATURUS AND FRUCTUS PONICIRI TRIFOLIATAE IMMATURUS BY FLOW-INJECTION WITH ULTRAVIOLET SPECTROSCOPIC DETECTION AND PROTON NUCLEAR MAGNETIC RESONANCE USING PARTIAL LEAST-SQUARES DISCRIMINANT ANALYSIS.

    Science.gov (United States)

    Zhang, Mengliang; Zhao, Yang; Harrington, Peter de B; Chen, Pei

    2016-03-01

    Two simple fingerprinting methods, flow-injection coupled to ultraviolet spectroscopy and proton nuclear magnetic resonance, were used for discriminating between Aurantii fructus immaturus and Fructus poniciri trifoliatae immaturus. Both methods were combined with partial least-squares discriminant analysis. In the flow-injection method, four data representations were evaluated: total ultraviolet absorbance chromatograms, averaged ultraviolet spectra, absorbance at 193, 205, 225, and 283 nm, and absorbance at 225 and 283 nm. Prediction rates of 100% were achieved for all data representations by partial least-squares discriminant analysis using leave-one-sample-out cross-validation. The prediction rate for the proton nuclear magnetic resonance data by partial least-squares discriminant analysis with leave-one-sample-out cross-validation was also 100%. A new validation set of data was collected by flow-injection with ultraviolet spectroscopic detection two weeks later and predicted by partial least-squares discriminant analysis models constructed by the initial data representations with no parameter changes. The classification rates were 95% with the total ultraviolet absorbance chromatograms datasets and 100% with the other three datasets. Flow-injection with ultraviolet detection and proton nuclear magnetic resonance are simple, high throughput, and low-cost methods for discrimination studies.

  7. Analysis for urinary catecholamines by liquid chromatography with amperometric detection: methodology and clinical interpretation of results.

    Science.gov (United States)

    Moyer, T P; Jiang, N S; Tyce, G M; Sheps, S G

    1979-02-01

    A method is presented for the quantitative analysis of urinary unconjugated norepinephrine, epinephrine, and dopamine as discrete entities. The procedure requires initial purification of the specimen on aluminum oxide and a boric acid-gel. We used "high-performance" reversed-phase paired-ion chromatography, with a flow-through amperometric cell as the detector. The CV was 6% for determination of norepinephrine, 11% for epinephrine, and 6% for dopamine monitored at physiologic concentrations of these compounds in urine. In a population study, urine specimens from 117 normal pediatric and adult subjects, 85 hypertensive patients, and 22 patients with surgically proved pheochromocytoma were analyzed. The specificity of the method for detection of pheochromocytoma was 100%, with a sensitivity of 97%.

  8. Design and properties of a flow-injection analysis cell using potassium-selective ionsensitive field-effect transistors as detection elements

    NARCIS (Netherlands)

    van der Wal, Peter D.; van der Wal, P.D.; Sudhölter, Ernst J.R.; Sudholter, Ernst; Reinhoudt, David

    1991-01-01

    The combination of flow-injection analysis (FIA) and chemically modified ion-sensitive field-effect transistors (CHEMFETs) is described. In a wall-jet cell, two identical potassium-selective CHEMFETs were used for a differential measurement using a platinum (pseudo-)reference electrode.

  9. Amperometric Immunosensor Based on a Protein A/Deposited Gold Nanocrystals Modified Electrode for Carbofuran Detection

    Directory of Open Access Journals (Sweden)

    Xia Sun

    2011-12-01

    Full Text Available In this paper, an amperometric immunosensor modified with protein A/deposited gold nanocrystals (DpAu was developed for the ultrasensitive detection of carbofuran residues. First, DpAu were electrodeposited onto the Au electrode surface to absorb protein A (PA and improve the electrode conductivity. Then PA was dropped onto the surface of DpAu film, used for binding antibody Fc fragments. Next, anti-carbofuran monoclonal antibody was immobilized on the PA modified electrode. Finally, bovine serum albumin (BSA was employed to block the possible remaining active sites avoiding any nonspecific adsorption. The fabrication procedure of the immunosensor was characterized by electrochemical impedance spectroscopy (EIS and cyclic voltammetry (CV, respectively. With the excellent electroconductivity of DpAu and the PA’s oriented immobilization of antibodies, a highly efficient immuno-reaction and detection sensitivity could be achieved. The influences of the electrodeposition time of DpAu, pH of the detection solution and incubation time on the current response of the fabricated immunosensor were investigated. Under optimized conditions, the current response was proportional to the concentration of carbofuran which ranged from 1 to 100 ng/mL and 100 ng/mL to 100 μg/mL. The detection limit was 0.1924 ng/mL. The proposed carbofuran immnuosensor exhibited high specificity, reproducibility, stability and regeneration performance, which may open a new door for ultrasensitive detection of carbofuran residues in vegetables and fruits.

  10. Amperometric immunosensor based on a protein A/deposited gold nanocrystals modified electrode for carbofuran detection.

    Science.gov (United States)

    Sun, Xia; Zhu, Ying; Wang, Xiangyou

    2011-01-01

    In this paper, an amperometric immunosensor modified with protein A/deposited gold nanocrystals (DpAu) was developed for the ultrasensitive detection of carbofuran residues. First, DpAu were electrodeposited onto the Au electrode surface to absorb protein A (PA) and improve the electrode conductivity. Then PA was dropped onto the surface of DpAu film, used for binding antibody Fc fragments. Next, anti-carbofuran monoclonal antibody was immobilized on the PA modified electrode. Finally, bovine serum albumin (BSA) was employed to block the possible remaining active sites avoiding any nonspecific adsorption. The fabrication procedure of the immunosensor was characterized by electrochemical impedance spectroscopy (EIS) and cyclic voltammetry (CV), respectively. With the excellent electroconductivity of DpAu and the PA's oriented immobilization of antibodies, a highly efficient immuno-reaction and detection sensitivity could be achieved. The influences of the electrodeposition time of DpAu, pH of the detection solution and incubation time on the current response of the fabricated immunosensor were investigated. Under optimized conditions, the current response was proportional to the concentration of carbofuran which ranged from 1 to 100 ng/mL and 100 ng/mL to 100 μg/mL. The detection limit was 0.1924 ng/mL. The proposed carbofuran immnuosensor exhibited high specificity, reproducibility, stability and regeneration performance, which may open a new door for ultrasensitive detection of carbofuran residues in vegetables and fruits.

  11. Open Tubular Microreactor with Enzyme Functionalized Micro- fluidic Channel for Amperometric Detection of Glucose

    Institute of Scientific and Technical Information of China (English)

    张蕾; 曲平; 盛金; 雷建平; 鞠烷先

    2012-01-01

    A simple and efficient method using enzyme immobilized microfluidic channel as open tubular microreactor was designed for amperometric detection of glucose. The microreactor was composed of a polydimethylsilicone/ glass hybrid device with three reservoirs, a cooling cave and a 6 cm capillary with a sampling fracture as micro-channel. The microchannel was further modified by thermal polymerization, followed by covalently attaching with glucose oxidase. Through fracture sampling and electrochromatography separation, the production via enzymatic reaction was determinated by Pt electrode at the end of capillary. The linear range for the detection of glucose was 0.05--7.5 mmol·L-1 with detection limit of 23μmol.L-1 The inter-and intra-chip reproducibilities for determination of 2.5 mmol-L-1 glucose were 98.5% (n=5) and 96.0% (n=5), respectively. With the advantage of flexible assembly, rapid efficiency, good stability and low-cost, this microreactor provided a potential platform for estab- lishing a portable enzyme-based chemical detection system in practical application.

  12. Amperometric detection of lactose using β-galactosidase immobilized in layer-by-layer films.

    Science.gov (United States)

    Campos, Paula P; Moraes, Marli L; Volpati, Diogo; Miranda, Paulo B; Oliveira, Osvaldo N; Ferreira, Marystela

    2014-07-23

    A direct, low-cost method to determine the concentration of lactose is an important goal with possible impact in various types of industry. In this study, a biosensor is reported that exploits the specific interaction between lactose and the enzyme β-galactosidase (β-Gal) normally employed to process lactose into glucose and galactose for lactose-intolerant people. The biosensor was made with β-Gal immobilized in layer-by-layer (LbL) films with the polyelectrolyte poly(ethylene imine) (PEI) and poly(vinyl sufonate) (PVS) on an indium tin oxide (ITO) electrode modified with a layer of Prussian Blue (PB). With an ITO/PB/(PEI/PVS)1(PEI/β-Gal)30 architecture, lactose could be determined with an amperometric method with sensitivity of 0.31 μA mmol(-1) cm(-2) and detection limit of 1.13 mmol L(-1), which is sufficient for detecting lactose in milk and for clinical exams. Detection occurred via a cascade reaction involving glucose oxidase titrated as electrolytic solution in the electrochemical cell, while PB allowed for operation at 0.0 V versus saturated calomel electrode, thus avoiding effects from interfering species. Sum-frequency generation spectroscopy data for the interface between the LbL film and a buffer containing lactose indicated that β-Gal lost order, which is the first demonstration of structural effects induced by the molecular recognition interaction with lactose.

  13. Determination of Four Active Ingredients in Vc Yinqiao Tablets by Capillary Zone Electrophoresis with Amperometric Detection

    Institute of Scientific and Technical Information of China (English)

    L(U),Jin; WANG,Qing-Jiang; CHENG,Xi; LIU,Hai-Yan; HE,Pin-Gang; FANG,Yu-Zhi

    2006-01-01

    A simple, reliable and reproducible method, based on capillary zone electrophoresis with amperometric detection (CZE-AD), has been developed for simultaneous determination of four active ingredients in Vc Yinqiao tablets including paracetamol, vitamin C, caffeic acid and chlorogenic acid. A carbon-disk electrode was used as working electrode and 0.95 V (versus SCE) was selected as detection potential. The optimal conditions of CZE experiment were 30 mmol·L-1 borate solution (pH 9.5) as running buffer, 14 kV as separation voltage and 8 s (14 kV) as electro-kinetic sampling time. Under the selected optimum conditions, paracetamol, vitamin C, caffeic acid and chlorogenic acid could be perfectly separated within 22 min, and their detection limits (S/N=3) ranged from 5 × 10-7 to 1×10-6 mol·L-1. This proposed method demonstrated good reproducibility with relative standard deviations of less than 3% for both migration time and peak current (n=7). The utility of this method was demonstrated by monitoring a kind of compound medicine named Vc Yinqiao tablets and the assay results were satisfactory.

  14. Characterization of Hardwood-Derived Carboxymethylcellulose by High pH Anion Chromatography Using Pulsed Amperometric Detection

    OpenAIRE

    2010-01-01

    An approach for the quantitative analysis of substituent distribution in carboxymethylcellulose (CMC) is presented. In short, the high-pH anion-exchange chromatography method, coupled to pulsed amperometric detection (PAD), is introduced. Each of the seven derivatives in CMC is presented by a single peak on the PAD trace, thus enabling an easy quantification. New inside information on monomer composition is obtained by this novel method, which is essential for understanding the structure vers...

  15. Nanostructured cupric oxide electrode: An alternative to amperometric detection of carbohydrates in anion-exchange chromatography.

    Science.gov (United States)

    Barragan, José T C; Kubota, Lauro T

    2016-02-01

    In this paper, a new and low cost copper/cupric oxide nanostructured electrode is presented as an alternative to the amperometric detection of carbohydrates in high-performance anion exchange chromatography. The modified copper electrodes were prepared by a simple and fast method which resulted in the obtainment of homogeneously distributed nanostructures adhered to the surface with controlled chemical nature. The results, when compared to conventional copper electrodes, exhibited considerable improvements in analytical results, including: 1) Better repeatability in consecutive glucose detections, in which the percent relative standard deviation improved from 15.1% to 0.279%. 2) Significant improvements in the stability of the baseline and a decrease of the stabilization time, going from several hours to approximately 15 min. 3) Considerable increase in the sensitivity towards glucose, from 5.02 nA min mg L(-1) to 25.5 nA min mg L(-1). 4) Improvements in the detectability with limits as low as 1.09 pmol. 5) Wide working range of concentrations (1 × 10(-2) to 1 × 10(4) mg L(-1)). 6) Good linearity with correlation coefficients greater than 0.998. 7) Possibility of detecting different molecules of carbohydrates (lactose, maltose, sucrose cellobiose, sorbitol, fructose, glucose, galactose, manose, arabitol, xylose, ribose and arabnose). In comparison to the electrode that is more employed for this type of application (gold electrode), the low cost, the possibility of detection at constant potential and the equivalent detection limits presented by the new electrode material introduced in this work emerge as characteristics that make this material a powerful alternative considering the detection of carbohydrates in anion exchange chromatography.

  16. Analysis of Trace Ingredients in Green Tea by Capillary Electrophoresis with Amperometric Detection

    Institute of Scientific and Technical Information of China (English)

    LI Ping; DONG Shu-Qing; WANG Qing-Jiang; FANG Yu-Zhi

    2008-01-01

    In this paper, four trace ingredients (rutin, gallic acid, quercetin, chlorogenic acid) in green tea were simultaneously determined by capillary electrophoresis coupled with amperometric detection (CE-AD). Effects of several important factors such as the pH and concentration of running buffer, separation voltage, injection time and detection potential were investigated to acquire the optimum conditions. Under the optimum conditions, the analytes could be separated within 20 min at a separation voltage of 18 kV in a 60 mmol/L borate buffer (pH 8.7). A 300 μmdiameter carbon disk electrode generated good responses at 950 mV (vs. SCE) for all analytes. The relationship between the peak currents and concentrations of the analytes was linear over about three orders of magnitude with demonstrated long-term stability and reproducibility with relative standard deviations less than 3% for both migration time and peak current (n=7), which could be successfully used for the determination of the analytes in green tea with satisfactory assay results.

  17. Characterisation of brewpub beer carbohydrates using high performance anion exchange chromatography coupled with pulsed amperometric detection.

    Science.gov (United States)

    Arfelli, Giuseppe; Sartini, Elisa

    2014-01-01

    High performance anion exchange chromatography (HPAEC) coupled with pulsed amperometric detection (PAD) was optimised in order to quantify mannose, maltose, maltotriose, maltotetraose, maltopentaose, maltohexaose and maltoheptaose content of beer. The method allows the determination of above mentioned oligosaccharides, in a single chromatographic run, without any pre-treatment. Limit of detection and limit of quantification were suitable for beer. Accuracy and repeatability were good for the entire amount considered. Once optimised HPAEC PAD for the specific matrix, the second goal of this research was to verify the possibility to discriminate beers, depending on their style. The carbohydrates content of brewpub commercial beers was very variable, ranging from 19.3 to 1469mg/L (mannose), 34.5 to 2882mg/L (maltose), 141.9 to 20731mg/L (maltotriose), 168.5 to 7650mg/L (maltotetraose), 20.1 to 2537mg/L (maltopentaose), 22.9 to 3295mg/L (maltohexaose), 8.5 to 2492mg/L (maltoeptaose), even in the same style of beer. However, the carbohydrates content was useful, jointed with other compounds amount, to discriminate different styles of beer. As a matter of fact, principal component analysis put in evidence beer differences considering some fermentation conditions and colour.

  18. Fast determination of aldehyde preservatives by miniaturized capillary electrophoresis with amperometric detection.

    Science.gov (United States)

    Li, Ying; Chen, Fang; Ge, Jinyuan; Tong, Fanghong; Deng, Zhaoyue; Shen, Fengwu; Gu, Qianxia; Ye, Jiannong; Chu, Qingcui

    2014-02-01

    A novel miniaturized CE with amperometric detection (mini-CE-AD) method has been developed for fast determination of aliphatic aldehyde preservatives, namely formaldehyde and glyoxal, in commodities. After derivatization with an electroactive compound 2-thiobarbituric acid, these two nonelectroactive aldehydes were converted to electroactive adducts, therefore detectable by mini-CE-AD approach. Under the optimum conditions, two aldehydes can be well-separated with the coexisting interferents as well as their homologs (acetaldehyde and methyl-glyoxal), and the LODs (S/N = 3) were achieved at nanogram-per-milliliter level (1.64-2.80 ng/mL) based on the online enrichment method of transient moving chemical reaction boundary. The proposed method has been applied for the analyses of above aldehyde preservatives in different real commodity samples including skincare products, baby lotion, and toothpaste, and the average recoveries were in the range of 94-105%, which should find a wide range of analytical applications as an alternative to conventional and microchip CE approaches.

  19. Photometric flow injection determination of phosphate on a PDMS microchip using an optical detection system assembled with an organic light emitting diode and an organic photodiode.

    Science.gov (United States)

    Liu, Rong; Ishimatsu, Ryoichi; Yahiro, Masayuki; Adachi, Chihaya; Nakano, Koji; Imato, Toshihiko

    2015-01-01

    and a good linear relationship between the concentration and absorbance was observed in the concentration range 0-0.2 ppm, with a detection limit (S/N=3) of 0.02 ppm. The assembled photometric detector was also applied to the determination of phosphate by the flow injection of river water samples using the reagent solution containing MG and molybdenum ammonium in sulfuric acid. A good recovery (97-99%) for the river water samples, which had been spiked with the standard 0.08 ppm, with an RSD of ca 5% (n=5) was obtained using the constructed system. Copyright © 2014 Elsevier B.V. All rights reserved.

  20. A New Method for Decreasing Mass Limit of Detection and Increasing Number of Theoretical Plates in Capillary Electrophoresis with Amperometric Detection

    Institute of Scientific and Technical Information of China (English)

    2003-01-01

    A new method was developed to decrease the mass limit of detection (LOD) and increase the number of theoretical plates (N) in capillary electrophoresis with amperometric detection. When the single microcylinder electrode, the 10 μm ID capillary with the etched detection end and the in-capillary alignment were used, the mass LOD for phenol was reduced 124 times and N was increased 36 times in comparison with the normal situation.

  1. Electrochemical study and flow injection analysis of paracetamol in pharmaceutical formulations based on screen-printed electrodes and carbon nanotubes

    Energy Technology Data Exchange (ETDEWEB)

    Fanjul-Bolado, Pablo [DropSens, S.L., Edificio Severo Ochoa, Campus El Cristo, 33006 Oviedo, Asturias (Spain); Lamas-Ardisana, Pedro Jose [Departamento de Quimica Fisica y Analitica, Universidad de Oviedo, Julian Claveria 8, 33006 Oviedo, Asturias (Spain); Hernandez-Santos, David [DropSens, S.L., Edificio Severo Ochoa, Campus El Cristo, 33006 Oviedo, Asturias (Spain); Costa-Garcia, Agustin, E-mail: costa@fq.uniovi.es [Departamento de Quimica Fisica y Analitica, Universidad de Oviedo, Julian Claveria 8, 33006 Oviedo, Asturias (Spain)

    2009-04-13

    Acetaminophenol or paracetamol is one of the most commonly used analgesics in pharmaceutical formulations. Acetaminophen is electroactive and voltammetric mechanistic studies for the electrode processes of the acetaminophenol/N-acetyl-p-quinoneimine redox system are presented. Carbon nanotubes modified screen-printed electrodes with enhanced electron transfer properties are used for the study of the electrochemical-chemical oxidation mechanism of paracetamol at pH 2.0. Quantitative analysis of paracetamol by using its oxidation process (in a Britton-Robinson buffer solution pH 10.0) at +0.20 V (vs. an Ag pseudoreference electrode) on an untreated screen-printed carbon electrode (SPCE) was carried out. Thus, a cyclic voltammetric based reproducible determination of acetaminophen (R.S.D., 2.2%) in the range 2.5 x 10{sup -6} M to 1 x 10{sup -3} M, was obtained. However, when SPCEs are used as amperometric detectors coupled to a flow injection analysis (FIA) system, the detection limit achieved for paracetamol was 1 x 10{sup -7} M, one order of magnitude lower than that obtained by voltammetric analysis. The repeatability of the amperometric detection with the same SPCE is 2% for 15 successive injections of 10{sup -5} M acetaminophen and do not present any memory effect. Finally, the applicability of using screen-printed carbon electrodes for the electrochemical detection of paracetamol (i.e. for quality control analysis) was demonstrated by using two commercial pharmaceutical products.

  2. Determination of amitrole and urazole in water samples by capillary zone electrophoresis using simultaneous UV and amperometrical detection.

    Science.gov (United States)

    Chicharro, M; Moreno, M; Bermejo, E; Ongay, S; Zapardiel, A

    2005-12-16

    In this paper, capillary zone electrophoresis with amperometric detection (CZE-AD) was first applied to the simultaneous separation and determination of amitrole and urazole in water samples. A simple end-column electrochemical detector was used in combination with a commercially available capillary electrophoresis instrument with UV detection. The effects of several important factors were investigated to find optimum conditions. A carbon disk electrode was used as working electrode. Separation and determination of these compounds in water samples were performed in 0.030 mol l(-1) acetate buffers at pH 4.5, 25 kV as separation voltage and the samples were introduced by hydrodynamic mode for 1.5 s. Most of the studies realized showed that the direct electrochemical detection is more sensitive and selective than UV detection. Under the optimum conditions, excellent linearity was observed between peak amperometric signal and analyte concentrations in the range of 0.19-1.35 mg l(-1) for amitrole and 0.20-1.62 mg l(-1) for urazole. The detection limits were 63 and 68 microg l(-1) for amitrole and urazole, respectively. The utility of this method was demonstrated by monitoring water samples, and the assay results were satisfactory. The detection limits using a previous preconcentration step for amitrole and urazole in spiked mineral water samples were 0.6 and 1.0 microg l(-1) for amitrole and urazole, respectively.

  3. A review of enzymatic uric acid biosensors based on amperometric detection.

    Science.gov (United States)

    Erden, Pınar Esra; Kılıç, Esma

    2013-03-30

    This review summarizes the studies carried on the development of amperometric uric acid biosensors over the past twenty years. Sensing principles, enzyme immobilization techniques, the electrode types, different approaches and various matrices used for biosensor fabrication are presented along with their benefits and limitations. Uric acid biosensors based on different modes of transducing devices such as optical, potentiometric, conductometric are also referred.

  4. Amperometric cell for subcutaneous detection of hydrogen sulfide in anesthetized experimental animals.

    Science.gov (United States)

    Nagy, L; Filotás, D; Boros, M; Pozsgai, G; Pintér, E; Nagy, G

    2014-12-01

    Hydrogen sulfide (H2S) is a toxic gas. It has been recognized that H2S evolving in biochemical reactions in living organisms has an important role in different physiologic processes. Nowadays, H2S is known as an endogenous messenger molecule. Natural sulfurous spring water has been proved beneficial in the therapy of diseases of the skin and other organs (Boros et al 2013). In vivo real-time detection of local H2S concentration is an important but challenging task.We developed a two-electrode amperometric cell for selective subcutaneous detection of H2S in anesthetized mice. The cell is a small size implantable gas sensor containing a platinum disc anode and a silver cathode. The selectivity is provided by a membrane permeable only by gases. There is a buffered reversible electrochemical mediator solution in an oxidized form inside the cell. As gaseous H2S penetrates into the cell the mediator is reduced, and +0.4 V versus the reference is employed on the platinum working electrode. The reduced mediator is oxidized on the anode surface. The current provides an analytical signal representing the concentration of H2S.Appropriate shape, size and membrane material were selected, and optimal working parameters--such as mediator concentration, pH and cell voltage--were determined in vitro. The lower limit of detection in the stirred sample solution at pH = 5.5 was as small as 9.4 × 10(-7) M and a dynamic concentration range of 0-6 × 10(-4) M could be achieved.The detecting surfaces of the cell were covered with freshly dissected mouse skin to test dermal H2S permeability. In other experiments, the cell was implanted subcutaneously in an anesthetized mouse and the animal was submerged in a buffer solution containing different concentrations of H2S so that the skin surface over the sensor was covered by the solution. Measurements of subcutaneous H2S concentration were taken. The experiments clearly proved that H2S diffuses through the skin of the live mouse.

  5. Critical Evaluation of Acetylcholine Determination in Rat Brain Microdialysates using Ion-Pair Liquid Chromatography with Amperometric Detection

    Directory of Open Access Journals (Sweden)

    Yvette Michotte

    2008-08-01

    Full Text Available Liquid chromatography with amperometric detection remains the most widely used method for acetylcholine quantification in microdialysis samples. Separation of acetylcholine from choline and other matrix components on a microbore chromatographic column (1 mm internal diameter, conversion of acetylcholine in an immobilized enzyme reactor and detection of the produced hydrogen peroxide on a horseradish peroxidase redox polymer coated glassy carbon electrode, achieves sufficient sensitivity for acetylcholine quantification in rat brain microdialysates. However, a thourough validation within the concentration range required for this application has not been carried out before. Furthermore, a rapid degradation of the chromatographic columns and enzyme systems have been reported. In the present study an ion-pair liquid chromatography assay with amperometric detection was validated and its long-term stability evaluated. Working at pH 6.5 dramatically increased chromatographic stability without a loss in sensitivity compared to higher pH values. The lower limit of quantification of the method was 0.3 nM. At this concentration the repeatability was 15.7%, the inter-day precision 8.7% and the accuracy 103.6%. The chromatographic column was stable over 4 months, the immobilized enzyme reactor up to 2-3 months and the enzyme coating of the amperometric detector up to 1-2 months. The concentration of acetylcholine in 30 μl microdialysates obtained under basal conditions from the hippocampus of freely moving rats was 0.40 ± 0.12 nM (mean ± SD, n = 30. The present method is therefore suitable for acetylcholine determination in rat brain microdialysates.

  6. Separation of alditols of interest in food products by high-performance anion-exchange chromatography with pulsed amperometric detection.

    Science.gov (United States)

    Corradini, C; Canali, G; Cogliandro, E; Nicoletti, I

    1997-12-12

    High-performance anion-exchange chromatography (HPAEC)-pulsed amperometric detection (PAD) employing a CarboPac MA 1 column was investigated with respect to mobile phase composition, linear response characteristics, repeatability, reproducibility and sensitivity with different alditols used as sugar substitutes in food and confectionery products. The energy-reduced bulk sweeteners isomalt and maltitol were well resolved in less than 25 min by isocratic elution with 600 mM sodium hydroxide solution. HPAEC-PAD was also successfully applied to the determination of alditols in sugar-free products and a low-calorie sweetener containing sorbitol, mannitol and fructose at different levels.

  7. Highly selective amperometric sensor for the trace level detection of hydrazine at bismuth nanoparticles decorated graphene nanosheets modified electrode.

    Science.gov (United States)

    Devasenathipathy, Rajkumar; Mani, Veerappan; Chen, Shen-Ming

    2014-06-01

    A highly selective amperometric sensor was developed for the trace level determination of hydrazine at bismuth nanoparticles (Bi) decorated graphene nanosheets (GR) composite film modified glassy carbon electrode (GCE). GR-Bi nanocomposite has been successfully prepared via simple and facile chemical reduction approach and its structure was characterized by various techniques. Surface morphological and X-ray diffraction studies revealed the formation and high loading of Bi nanoparticles on graphene sheets. GR-Bi nanocomposite modified GCE exhibited greatly enhanced electrocatalytic performance towards electro-oxidation of hydrazine in terms of decrease in overpotential and increase in oxidation peak current (Ip). The kinetic parameters such as electron transfer coefficient (α) and diffusion coefficient (Do) of the hydrazine oxidation were determined to be 0.70 and 2.65×10(-5) cm(2) s(-1), respectively. An amperometric sensor has been fabricated which detects trace level concentration of hydrazine. The sensor exhibited a wide linear range from 20 nM to 0.28 mM and a very low detection limit (LOD) of 5 nM. Remarkably, this is the lowest LOD achieved for the determination of hydrazine in neutral pH among other reported electrochemical hydrazine sensors. In addition, the sensor selectively detects hydrazine even in the presence of 1000 fold excess quantity of common interferrants. The practical feasibility of the sensor has been assessed in water and urine samples with good recoveries. Furthermore, the sensor exhibited appreciable stability, repeatability and reproducibility results.

  8. Determination of Zinc-Based Additives in Lubricating Oils by Flow-Injection Analysis with Flame-AAS Detection Exploiting Injection with a Computer-Controlled Syringe.

    Science.gov (United States)

    Pignalosa, Gustavo; Knochen, Moisés; Cabrera, Noel

    2005-01-01

    A flow-injection system is proposed for the determination of metal-based additives in lubricating oils. The system, operating under computer control uses a motorised syringe for measuring and injecting the oil sample (200 muL) in a kerosene stream, where it is dispersed by means of a packed mixing reactor and carried to an atomic absorption spectrometer which is used as detector. Zinc was used as model analyte. Two different systems were evaluated, one for low concentrations (range 0-10 ppm) and the second capable of providing higher dilution rates for high concentrations (range 0.02%-0.2% w/w). The sampling frequency was about 30 samples/h. Calibration curves fitted a second-degree regression model (r(2) = 0.996). Commercial samples with high and low zinc levels were analysed by the proposed method and the results were compared with those obtained with the standard ASTM method. The t test for mean values showed no significant differences at the 95% confidence level. Precision (RSD%) was better than 5% (2% typical) for the high concentrations system. The carryover between successive injections was found to be negligible.

  9. Investigation of iron(III) reduction and trace metal interferences in the determination of dissolved iron in seawater using flow injection with luminol chemiluminescence detection

    Energy Technology Data Exchange (ETDEWEB)

    Ussher, Simon J. [School of Earth, Ocean and Environmental Sciences (SEOES), University of Plymouth, Drake Circus, Plymouth PL4 8AA (United Kingdom); Milne, Angela [School of Earth, Ocean and Environmental Sciences (SEOES), University of Plymouth, Drake Circus, Plymouth PL4 8AA (United Kingdom); Department of Oceanography, Florida State University, Tallahassee, FL 32306-4320 (United States); Landing, William M. [Department of Oceanography, Florida State University, Tallahassee, FL 32306-4320 (United States); Attiq-ur-Rehman, Kakar [Department of Chemistry, University of Balochistan, Quetta (Pakistan); Seguret, Marie J.M.; Holland, Toby [School of Earth, Ocean and Environmental Sciences (SEOES), University of Plymouth, Drake Circus, Plymouth PL4 8AA (United Kingdom); Achterberg, Eric P. [National Oceanography Centre, University of Southampton, European Way, Southampton SO14 3ZH (United Kingdom); Nabi, Abdul [Department of Chemistry, University of Balochistan, Quetta (Pakistan); Worsfold, Paul J., E-mail: pworsfold@plymouth.ac.uk [School of Earth, Ocean and Environmental Sciences (SEOES), University of Plymouth, Drake Circus, Plymouth PL4 8AA (United Kingdom)

    2009-10-12

    A detailed investigation into the performance of two flow injection-chemiluminescence (FI-CL) manifolds (with and without a preconcentration column) for the determination of sub-nanomolar dissolved iron (Fe(II) + Fe(III)), following the reduction of Fe(III) by sulphite, in seawater is described. Kinetic experiments were conducted to examine the efficiency of reduction of inorganic Fe(III) with sulphite under different conditions and a rigorous study of the potential interference caused by other transition metals present in seawater was conducted. Using 100 {mu}M concentrations of sulphite a reduction time of 4 h was sufficient to quantitatively reduce Fe(III) in seawater. Under optimal conditions, cobalt(II) and vanadium(IV)/(III) were the major positive interferences and strategies for their removal are reported. Specifically, cobalt(II) was masked by the addition of dimethylglyoxime to the luminol solution and vanadium(IV) was removed by passing the sample through an 8-hydroxyquinoline column in a low pH carrier stream. Manganese(II) also interfered by suppression of the CL response but this was not significant at typical open ocean concentrations.

  10. Amperometric Immunosensor for Carbofuran Detection Based on MWCNTs/GS-PEI-Au and AuNPs-Antibody Conjugate

    Directory of Open Access Journals (Sweden)

    Xiangyou Wang

    2013-04-01

    Full Text Available In this paper, an amperometric immunosensor for the detection of carbofuran was developed. Firstly, multiwall carbon nanotubes (MWCNTs and graphene sheets-ethyleneimine polymer-Au (GS-PEI-Au nanocomposites were modified onto the surface of a glass carbon electrode (GCE via self-assembly. The nanocomposites can increase the surface area of the GCE to capture a large amount of antibody, as well as produce a synergistic effect in the electrochemical performance. Then the modified electrode was coated with gold nanoparticles-antibody conjugate (AuNPs-Ab and blocked with BSA. The monoclonal antibody against carbofuran was covalently immobilized on the AuNPs with glutathione as a spacer arm. The morphologies of the GS-PEI-Au nanocomposites and the fabrication process of the immunosensor were characterized by X-ray diffraction (XRD, ultraviolet and visible absorption spectroscopy (UV-vis and scanning electron microscopy (SEM, respectively. Under optimal conditions, the immunosensor showed a wide linear range, from 0.5 to 500 ng/mL, with a detection limit of 0.03 ng/mL (S/N = 3. The as-constructed immunosensor exhibited notable performance features such as high specificity, good reproducibility, acceptable stability and regeneration performance. The results are mainly due to the excellent properties of MWCNTs, GS-PEI-Au nanocomposites and the covalent immobilization of Ab with free hapten binding sites for further immunoreaction. It provides a new avenue for amperometric immunosensor fabrication.

  11. Amperometric immunosensor for carbofuran detection based on MWCNTs/GS-PEI-Au and AuNPs-antibody conjugate.

    Science.gov (United States)

    Zhu, Ying; Cao, Yaoyao; Sun, Xia; Wang, Xiangyou

    2013-04-19

    In this paper, an amperometric immunosensor for the detection of carbofuran was developed. Firstly, multiwall carbon nanotubes (MWCNTs) and graphene sheets-ethyleneimine polymer-Au (GS-PEI-Au) nanocomposites were modified onto the surface of a glass carbon electrode (GCE) via self-assembly. The nanocomposites can increase the surface area of the GCE to capture a large amount of antibody, as well as produce a synergistic effect in the electrochemical performance. Then the modified electrode was coated with gold nanoparticles-antibody conjugate (AuNPs-Ab) and blocked with BSA. The monoclonal antibody against carbofuran was covalently immobilized on the AuNPs with glutathione as a spacer arm. The morphologies of the GS-PEI-Au nanocomposites and the fabrication process of the immunosensor were characterized by X-ray diffraction (XRD), ultraviolet and visible absorption spectroscopy (UV-vis) and scanning electron microscopy (SEM), respectively. Under optimal conditions, the immunosensor showed a wide linear range, from 0.5 to 500 ng/mL, with a detection limit of 0.03 ng/mL (S/N = 3). The as-constructed immunosensor exhibited notable performance features such as high specificity, good reproducibility, acceptable stability and regeneration performance. The results are mainly due to the excellent properties of MWCNTs, GS-PEI-Au nanocomposites and the covalent immobilization of Ab with free hapten binding sites for further immunoreaction. It provides a new avenue for amperometric immunosensor fabrication.

  12. Amperometric sulfide detection using Coprinus cinereus peroxidase immobilized on screen printed electrode in an enzyme inhibition based biosensor.

    Science.gov (United States)

    Savizi, Iman Shahidi Pour; Kariminia, Hamid-Reza; Ghadiri, Mohammad; Roosta-Azad, Reza

    2012-05-15

    In the present work, an amperometric inhibition biosensor for the determination of sulfide has been fabricated by immobilizing Coprinus cinereus peroxidase (CIP) on the surface of screen printed electrode (SPE). Chitosan/acrylamide was applied for immobilization of peroxidase on the working electrode. The amperometric measurement was performed at an applied potential of -150 mV versus Ag/AgCl with a scan rate of 100 mV in the presence of hydroquinone as electron mediator and 0.1M phosphate buffer solution of pH 6.5. The variables influencing the performance of sensor including the amount of substrate, mediator concentration and electrolyte pH were optimized. The determination of sulfide can be achieved in a linear range of 1.09-16.3 μM with a detection limit of 0.3 μM. Developed sensor showed quicker response to sulfide compared to the previous developed sulfide biosensors. Common anions and cations in environmental water did not interfere with sulfide detection by the developed biosensor. Cyanide interference on the enzyme inhibition caused 43.25% error in the calibration assay which is less than the amounts reported by previous studies. Because of high sensitivity and the low-cost of SPE, this inhibition biosensor can be successfully used for analysis of environmental water samples.

  13. Microfabricated biosensor for the simultaneous amperometric and luminescence detection and monitoring of Ochratoxin A.

    Science.gov (United States)

    Tria, Scherrine A; Lopez-Ferber, David; Gonzalez, Catherine; Bazin, Ingrid; Guiseppi-Elie, Anthony

    2016-05-15

    The low molecular weight hapten, Ochratoxin A (OTA), is a natural carcinogenic mycotoxin produced by Aspergillus and Penicillium fungi and so it commonly appears in wines, other foods, and in the environment. An amperometric biosensor has been developed that uses the immobilized synthetic peptide, NFO4; which possesses a high binding affinity and thus provides for molecular recognition of OTA; simulating the mycotoxin-specific antibody. Biotransducers were produced from a microlithographically fabricated electrochemical cell-on-a-chip that uses the microdisc electrode array working electrode format augmented with microporous graphitized carbon (MGC) that was electrodeposited within a poly(aniline-co-meta-aminoaniline) electroconductive polymer layer. A redox mediator, iron-nickel hexacyanoferrate (Fe|NiHCF) was amperometrically deposited onto the MGC. The device was then dip-coated with monomer cocktail that yielded poly(HEMA-co-AEMA) foam that was prepared in-situ by UV crosslinking and by sequentially freezing followed by freeze drying of the chip to yield a 3-D support for the chelation of Zn(2+) ions (ZnCl2) and the subsequent immobilization of N-terminus his-tagged peptide, NFO4. To conduct the biosensors assay, HRP conjugated OTA was added to the free OTA solutions and together competitively incubated on the biospecific MDEA ECC 5037-Pt|MGC|HCF|Hydrogel-NFO4 biotransducer. The amperometric response to peroxide was determined after 5 min of enzymatic reaction following addition of standard substrate H2O2/luminol. Simultaneous analysis of light emission signals (λmax=425 nm) allowed direct comparison of amperometric and luminescence performance. Using chitosan foam and a luminescence bioassay we obtained maximum inhibition at 10 μg L(-1) and half inhibition occurred at 2.1 μg L(-1). Using poly(HEMA-co-AEMA) hydrogel and an amperometric bioassay (50s) we obtained maximum inhibition at 10 μg L(-1) and half inhibition occurred at 2.8 μg L(-1).

  14. Determination of ribavirin by flow injection chemiluminescence

    Institute of Scientific and Technical Information of China (English)

    Juqing Jin; Yuhai Tang; Langchong He; Hong Yao; Yuanyuan Sun

    2006-01-01

    Objective: To establish a rapid and precise continuous flow-injection chemiluminescence (CL) method to determine ribavirin. Methods: The ribavirin could restrain strongly CL reaction of luminol in sodium hydroxide (NaOH) solution with potassium chlorate(KClO3). The different experimental parameters affecting the CL intensity were studied carefully. Results:Under optimum conditions(The concentrations of luminol,KClO3, and NaOH were at 0.1 mmol/L,0.5 μmol/L,and 0.2 mol/L, respectively), the linear range of the working curves was 0.01-7.00 μg/ml with a detection limit of 0.004 μg/ml. Conclusion: The method is simple, rapid and sensitive, and successfully applied to the determination of ribavirin in pharmaceutical preparations and biological fluids.

  15. Simultaneous determination of electroactive and non-electroactive food preservatives by novel capillary electrophoresis with amperometric detection.

    Science.gov (United States)

    Wang, Weiyu; Wang, Yiping; Zhang, Junbo; Chu, Qingcui; Ye, Jiannong

    2010-09-23

    A novel capillary electrophoresis and amperometric detection method was achieved by adding an electroactive additive (3,4-dihydroxybenzylamine, 3,4-DHBA) to the running buffer, so that both electroactive and non-electroactive food preservatives were simultaneously determined. Under the selected optimum conditions, four electroactive preservatives (methylparaben, ethylparaben, propylparaben and butylparaben) and two non-electroactive preservatives (potassium sorbate and sodium lactate) were well separated and sensitively detected with detection limits (S/N=3) ranging from 1.06×10(-8) to 2.73×10(-6) g mL(-1). This method has been successfully employed for the determination of both electroactive and non-electroactive preservatives in several food commodities.

  16. Rapid separation and highly sensitive detection methodology for sulfonamides in shrimp using a monolithic column coupled with BDD amperometric detection.

    Science.gov (United States)

    Sangjarusvichai, Haruthai; Dungchai, Wijitar; Siangproh, Weena; Chailapakul, Orawon

    2009-09-15

    In this report, we aimed to extend our previous efforts toward the evaluation of sulfonamides (SAs) with a boron-doped diamond (BDD) electrode. We improved this method by reducing the analysis time using a monolithic column coupled with amperometric detection to determine seven sulfonamides (sulfaguanidine, sulfadiazine, sulfamethazine, sulfamonomethoxine, sulfamethoxazole, sulfadimethoxine and sulfaquinoxaline). Because of its rapid separation, low back-pressure and high separation efficiency compared to a particle-packed column, a monolithic column (100 mm x 4.6mm) was used for sulfonamide separation. Chromatographic separation was performed in less than 8 min. The analysis was carried out using phosphate buffer (0.1M, pH 3): acetonitrile: methanol in a ratio of 80:15:5 (v/v/v) as the mobile phase with a flow rate of 1.5 mL min(-1). The optimal detection potential using hydrodynamic voltammetry was found to be 1.2V versus Ag/AgCl. The method was applied to determine seven sulfonamides in shrimp after sample preparation by solid-phase extraction. The recoveries of the sulfonamides in spiked shrimp samples at 1.5, 5 and 10 microg g(-1) were in the range of 81.7 to 97.5% with a relative standard deviation (R.S.D.) between 1.0 and 4.6%. Our methodology produced results that were highly correlated with HPLC-MS data. Therefore, we propose a method that can be used for the rapid, selective and sensitive evaluation of sulfonamides in contaminated food.

  17. Flow Injection Analysis: A Revolution in Modern Analytical Chemistry

    DEFF Research Database (Denmark)

    Hansen, Elo Harald

    1996-01-01

    A review is made of the fundamentals of Flow Injection Analysis (FIA), and the versatility and applicability of this analytical concept is demonstrated by a series of examples, comprizing the use of different types of FIA-manifolds and various detection devices (optical and electrochemical). Emph...

  18. A novel capillary electrophoresis microchip with amperometric detection using a Prussian blue-modified indium tin oxide electrode

    Science.gov (United States)

    Kim, Ju-Ho; Kang, C. J.; Kim, Yong-Sang

    2005-03-01

    A novel approach to construct a disposable capillary electrophoresis microchip is proposed. The electrocatalytic oxidation of dopamine at a Prussian blue (PB)-modified indium tin oxide (ITO) electrode was described and the amperometric detection of dopamine was then investigated. The PB film on ITO electrode was electrodeposited using FeCl3 and K3Fe(CN)6 mixed solution. Our results indicated that PB film was uniform, smooth, and defect-free. The CE-chip has been tested successfully by detecting dopamine and catechol within a very short time of around 80 sec using an electric field of 60 V/cm. The results also showed that dopamine and catechol mixtures were separated efficiently and rapidly. The microsystems gave a very good reproducibility for peak height and separation time. This microchip is cost effective and adequate for a disposable sensor.

  19. A high-performance polycarbonate electrophoresis microchip with integrated three-electrode system for end-channel amperometric detection.

    Science.gov (United States)

    Wang, Yurong; Chen, Hengwu; He, Qiaohong; Soper, Steven A

    2008-05-01

    A fully integrated polycarbonate (PC) microchip for CE with end-channel electrochemical detection operated in an amperometric mode (CE-ED) has been developed. The on-chip integrated three-electrode system consisted of a gold working electrode, an Ag/AgCl reference electrode and a platinum counter electrode, which was fabricated by photo-directed electroless plating combined with electroplating. The working electrode was positioned against the separation channel exit to reduce post-channel band broadening. The electrophoresis high-voltage (HV) interference with the amperometric detection was assessed with respect to detection noise and potential shifts at various working-to-reference electrode spacing. It was observed that the electrophoresis HV interference caused by positioning the working electrode against the channel exit could be diminished by using an on-chip integrated reference electrode that was positioned in close proximity (100 microm) to the working electrode. The CE-ED microchip was demonstrated for the separation of model analytes, including dopamine (DA) and catechol (CA). Detection limits of 132 and 164 nM were achieved for DA and CA, respectively, and a theoretical plate number of 2.5x10(4)/m was obtained for DA. Relative standard deviations in peak heights observed for five runs of a standard solution containing the two analytes (0.1 mM for each) were 1.2 and 3.1% for DA and CA, respectively. The chip could be continuously used for more than 8 h without significant deterioration in analytical performance.

  20. Detection and quantification of new psychoactive substances (NPSs) within the evolved "legal high" product, NRG-2, using high performance liquid chromatography-amperometric detection (HPLC-AD).

    Science.gov (United States)

    Zuway, Khaled Y; Smith, Jamie P; Foster, Christopher W; Kapur, Nikil; Banks, Craig E; Sutcliffe, Oliver B

    2015-09-21

    The global increase in the production and abuse of cathinone-derived New Psychoactive Substances (NPSs) has developed the requirement for rapid, selective and sensitive protocols for their separation and detection. Electrochemical sensing of these compounds has been demonstrated to be an effective method for the in-field detection of these substances, either in their pure form or in the presence of common adulterants, however, the technique is limited in its ability to discriminate between structurally related cathinone-derivatives (for example: (±)-4′-methylmethcathinone (4-MMC, 2a) and (±)-4′-methyl-N-ethylmethcathinone (4-MEC, 2b) when they are both present in a mixture. In this paper we demonstrate, for the first time, the combination of HPLC-UV with amperometric detection (HPLC-AD) for the qualitative and quantitative analysis of 4-MMC and 4-MEC using either a commercially available impinging jet (LC-FC-A) or custom-made iCell channel (LC-FC-B) flow-cell system incorporating embedded graphite screen-printed macroelectrodes. The protocol offers a cost-effective, reproducible and reliable sensor platform for the simultaneous HPLC-UV and amperometric detection of the target analytes. The two systems have similar limits of detection, in terms of amperometric detection [LC-FC-A: 14.66 μg mL(-1) (2a) and 9.35 μg mL(-1) (2b); LC-FC-B: 57.92 μg mL(-1) (2a) and 26.91 μg mL(-1) (2b)], to the previously reported oxidative electrochemical protocol [39.8 μg mL(-1) (2a) and 84.2 μg mL(-1) (2b)], for two synthetic cathinones, prevalent on the recreational drugs market. Though not as sensitive as standard HPLC-UV detection, both flow cells show a good agreement, between the quantitative electroanalytical data, thereby making them suitable for the detection and quantification of 4-MMC and 4-MEC, either in their pure form or within complex mixtures. Additionally, the simultaneous HPLC-UV and amperometric detection protocol detailed herein shows a marked improvement

  1. Development of a novel, sensitive amperometric-FIA glucose biosensor by packing up the amperometric cell with glucose oxidase modified anion exchange resin.

    Science.gov (United States)

    Su, Yuhua; Huang, Weixiong; Hu, Rongzong; Ding, Haodong; Hu, Kangkang

    2009-04-15

    In this work, the anion exchange resin (AER) was modified with a layer of glucose oxidase (GOD) and poly(diallyldimethylammonium chloride) (PDDA), respectively, via layer-by-layer electrostatic self-assembling strategy. The PDDA and GOD modified AER (PDDA/GOD/AER) was then packed into a home-made amperometric cell for flow injection analysis (FIA) of glucose. This design simplified the setup by integrating the enzyme reactor into the amperometric cell. And the AER in the cell behaved bifunctional, it was not only the support of enzymes, but also an anti-interference tool due to its retention effect toward ascorbic acid (AA) and uric acid (UA). A platinum modified porous titanium (Pt/PTi) electrode was utilized in the cell as the working electrode (WE), due to its large effective surface area it could increase the response by 8.3 times as compared with the planar pure platinum electrode. The proposed biosensor was very sensitive (22.4 microA cm(-2) mM(-1)) in glucose quantification, and the linear range was from 1 micromol L(-1) to 2 mmol L(-1) with the detection limit of 0.8 micromol L(-1). The biosensor was used for serum glucose determination, and the result obtained was satisfying. This work may have provided a reference design of the amperometric cell which could be adopted in other enzymatic-FIA biosensors.

  2. Micromachined Amperometric Nitrate Sensor

    OpenAIRE

    Dohyun Kim; Ira Goldberg; Jack Judy

    2003-01-01

    A nitrate-sensing system that consists of a micromachined sensor substrate, nitrate-permeable membrane, integrated microfluidic channels, and standard fluidic connectors has been designed, fabricated, assembled, and tested. Our microsensor was designed for in-situ monitoring of nitrate concentrations in ground water. A silver electrode was patterned for amperometric nitrate detection. An electrochemically oxidized silver electrode was used as a reference electrode. Microfluidic channels were ...

  3. Analysis of sugar phosphates in plants by ion chromatography on a titanium dioxide column with pulsed amperometric detection.

    Science.gov (United States)

    Sekiguchi, Yoko; Mitsuhashi, Naoto; Inoue, Yoshinori; Yagisawa, Hitoshi; Mimura, Tetsuro

    2004-06-11

    This paper describes the development of a practical method for the analysis of sugar phosphates from the model higher plant Arabidopsis thaliana by high-performance anion-exchange chromatography with pulsed amperometric detection (HPAEC-PAD). The extraction method of sugar phosphates from higher plants was first optimized for HPAEC-PAD analysis. In order to improve the resolution in HPAEC-PAD, a column packed with titanium dioxide resin was used. The titanium dioxide column was used as a trap-column for sugar phosphates and nucleotides, for the removal of sample matrices. Sample pretreatment was achieved in-line and automatically using a six-port valve placed after the injection valve.

  4. Influence of Self-Assembled Alkanethiol Monolayers on Stochastic Amperometric On-Chip Detection of Silver Nanoparticles.

    Science.gov (United States)

    Krause, Kay J; Adly, Nouran; Yakushenko, Alexey; Schnitker, Jan; Mayer, Dirk; Offenhäusser, Andreas; Wolfrum, Bernhard

    2016-04-01

    We investigate the influence of self-assembled alkanethiol monolayers at the surface of platinum microelectrode arrays on the stochastic amperometric detection of citrate-stabilized silver nanoparticles in aqueous solutions. The measurements were performed using a microelectrode array featuring 64 individually addressable electrodes that are recorded in parallel with a sampling rate of 10 kHz for each channel. We show that both the functional end group and the total length of the alkanethiol influence the charge transfer. Three different terminal groups, an amino, a hydroxyl, and a carboxyl, were investigated using two different molecule lengths of 6 and 11 carbon atoms. Finally, we show that a monolayer of alkanethiols with a length of 11 carbon atoms and a carboxyl terminal group can efficiently block the charge transfer of free nanoparticles in an aqueous solution.

  5. Determination of propoxur in environmental samples by automated solid-phase extraction followed by flow-injection analysis with tris(2,2'-bipyridyl)ruthenium(II) chemiluminescence detection

    Energy Technology Data Exchange (ETDEWEB)

    Perez-Ruiz, Tomas [Department of Analytical Chemistry, Faculty of Chemistry, University of Murcia, 30071 Murcia (Spain)]. E-mail: tpr@um.es; Martinez-Lozano, Carmen [Department of Analytical Chemistry, Faculty of Chemistry, University of Murcia, 30071 Murcia (Spain); Garcia, Maria Dolores [Department of Analytical Chemistry, Faculty of Chemistry, University of Murcia, 30071 Murcia (Spain)

    2007-02-19

    A sensitive method for the analysis of propoxur in environmental samples has been developed. It involves an automated solid-phase extraction (SPE) procedure using a Gilson Aspec XLi and flow-injection analysis (FI) with chemiluminescence (CL) detection. The FI-CL system relies on the photolysis of propoxur by irradiation using a low-pressure mercury lamp (main spectral line 254 nm). The resultant methylamine is subsequently detected by CL using tris(2,2'-bipyridyl)ruthenium(III), which is on-line generated by photo-oxidation of the ruthenium(II) complex in the presence of peroxydisulfate. The linear concentration range of application was 0.05-5 {mu}g mL{sup -1} of propoxur, with a detection limit of 5 ng mL{sup -1}. The repeatability was 0.82% expressed as relative standard deviation (n = 10) and the reproducibility, studied on 5 consecutive days, was 2.1%. The sample throughput was 160 injection per hour. Propoxur residues below ng mL{sup -1} levels could be determined in environmental water samples when an SPE preconcentration device was coupled on-line with the FI system. This SPE-FI-CL arrangement provides a detection limit as low as 5 ng L{sup -1} using only 500 mL of sample. In the analysis of fruits and vegetables, the detection limit was about 10 {mu}g kg{sup -1}.

  6. Determination of propoxur in environmental samples by automated solid-phase extraction followed by flow-injection analysis with tris(2,2'-bipyridyl)ruthenium(II) chemiluminescence detection.

    Science.gov (United States)

    Pérez-Ruiz, Tomás; Martínez-Lozano, Carmen; García, María Dolores

    2007-02-19

    A sensitive method for the analysis of propoxur in environmental samples has been developed. It involves an automated solid-phase extraction (SPE) procedure using a Gilson Aspec XLi and flow-injection analysis (FI) with chemiluminescence (CL) detection. The FI-CL system relies on the photolysis of propoxur by irradiation using a low-pressure mercury lamp (main spectral line 254 nm). The resultant methylamine is subsequently detected by CL using tris(2,2'-bipyridyl)ruthenium(III), which is on-line generated by photo-oxidation of the ruthenium(II) complex in the presence of peroxydisulfate. The linear concentration range of application was 0.05-5 microg mL(-1) of propoxur, with a detection limit of 5 ng mL(-1). The repeatability was 0.82% expressed as relative standard deviation (n=10) and the reproducibility, studied on 5 consecutive days, was 2.1%. The sample throughput was 160 injection per hour. Propoxur residues below ng mL(-1) levels could be determined in environmental water samples when an SPE preconcentration device was coupled on-line with the FI system. This SPE-FI-CL arrangement provides a detection limit as low as 5 ng L(-1) using only 500 mL of sample. In the analysis of fruits and vegetables, the detection limit was about 10 microg kg(-1).

  7. Non-invasive determination of glucose directly in raw fruits using a continuous flow system based on microdialysis sampling and amperometric detection at an integrated enzymatic biosensor.

    Science.gov (United States)

    Vargas, E; Ruiz, M A; Campuzano, S; Reviejo, A J; Pingarrón, J M

    2016-03-31

    A non-destructive, rapid and simple to use sensing method for direct determination of glucose in non-processed fruits is described. The strategy involved on-line microdialysis sampling coupled with a continuous flow system with amperometric detection at an enzymatic biosensor. Apart from direct determination of glucose in fruit juices and blended fruits, this work describes for the first time the successful application of an enzymatic biosensor-based electrochemical approach to the non-invasive determination of glucose in raw fruits. The methodology correlates, through previous calibration set-up, the amperometric signal generated from glucose in non-processed fruits with its content in % (w/w). The comparison of the obtained results using the proposed approach in different fruits with those provided by other method involving the same commercial biosensor as amperometric detector in stirred solutions pointed out that there were no significant differences. Moreover, in comparison with other available methodologies, this microdialysis-coupled continuous flow system amperometric biosensor-based procedure features straightforward sample preparation, low cost, reduced assay time (sampling rate of 7 h(-1)) and ease of automation.

  8. Microfluidics and nanoparticles based amperometric biosensor for the detection of cyanobacteria (Planktothrix agardhii NIVA-CYA 116) DNA.

    Science.gov (United States)

    Ölcer, Zehra; Esen, Elif; Ersoy, Aylin; Budak, Sinan; Sever Kaya, Dilek; Yağmur Gök, Mehmet; Barut, Serkan; Üstek, Duran; Uludag, Yildiz

    2015-08-15

    Some of the cyanobacteria produce protease inhibitor oligopeptides such as cyanopeptolins and cause drinking water contamination; hence, their detection has great importance to monitor the well-being of water sources that is used for human consumption. In the current study, a fast and sensitive nucleic acid biosensor assay has been described where cyanopeptolin coding region of one of the cyanobacteria (Planktothrix agardhii NIVA-CYA 116) genome has been used as target for monitoring of the fresh water resources. A biochip that has two sets of Au electrode arrays, each consist of shared reference/counter electrodes and 3 working electrodes has been used for the assay. The biochip has been integrated to a microfluidics system and all steps of the assay have been performed during the reagent flow to achieve fast and sensitive DNA detection. On-line hybridization of the target on to the capture probe immobilized surface resulted in a very short assay duration with respect to the conventional static assays. The binding of the avidin and enzyme modified Au nanoparticles to the biotinylated detection probe and the subsequent injection of the substrate enabled a real-time amperometric measurement with a detection limit of 6×10(-12) M target DNA (calibration curve r(2)=0.98). The developed assay enables fast and sensitive detection of cyanopeptolin producing cyanobacteria from freshwater samples and hence shows a promising technology for toxic microorganism detection from environmental samples.

  9. Analysis of polyphenols in white wine by CZE with amperometric detection using carbon nanotube-modified electrodes.

    Science.gov (United States)

    Moreno, Mónica; Arribas, Alberto Sánchez; Bermejo, Esperanza; Zapardiel, Antonio; Chicharro, Manuel

    2011-04-01

    A method for the simultaneous detection of five polyphenols (caffeic, chlorogenic, ferulic and gallic acids and (+)-catechin) by CZE with electrochemical detection was developed. Separation of these polyphenols was performed in a 100 mM borate buffer (pH 9.2) within 15 min. Under optimized separation conditions, the performance of glassy carbon (GC) electrodes modified with multiwalled carbon nanotube layer obtained from different dispersions was examined. GC electrode modified with a dispersion of multi-walled carbon nanotubes (CNT) in polyethylenimine has proven to be the most suitable CNT-based electrode for its application as amperometric detector for the CZE separation of the studied compounds. The excellent electrochemical properties of this electrode allowed the detection of the selected polyphenols at +200 mV and improved the efficiency and the resolution of their CZE separation. Limits of detection below 3.1 μM were obtained with linear ranges covering the 10⁻⁵ to 10⁻⁴  M range. The proposed method has been successfully applied for the detection (ferulic, caffeic and gallic acids and (+)-catechin) and the quantification (gallic acid and (+)-catechin) of polyphenols in two different white wines without any preconcentration step. A remarkable signal stability was observed on the electrode performance despite the presence of potential fouling substances in wine. Copyright © 2011 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  10. Recent advances in flow injection analysis.

    Science.gov (United States)

    Trojanowicz, Marek; Kołacińska, Kamila

    2016-04-07

    A dynamic development of methodologies of analytical flow injection measurements during four decades since their invention has reinforced the solid position of flow analysis in the arsenal of techniques and instrumentation of contemporary chemical analysis. With the number of published scientific papers exceeding 20,000, and advanced instrumentation available for environmental, food, and pharmaceutical analysis, flow analysis is well established as an extremely vital field of modern flow chemistry, which is developed simultaneously with methods of chemical synthesis carried out under flow conditions. This review work is based on almost 300 original papers published mostly in the last decade, with special emphasis put on presenting novel achievements from the most recent 2-3 years in order to indicate current development trends of this methodology. Besides the evolution of the design of whole measuring systems, and including especially new applications of various detections methods, several aspects of implications of progress in nanotechnology, and miniaturization of measuring systems for application in different field of modern chemical analysis are also discussed.

  11. Carbon Fiber Ultramicrodic Electrode Electrodeposited with Over-Oxidized Polypyrrole for Amperometric Detection of Vesicular Exocytosis from Pheochromocytoma Cell

    Science.gov (United States)

    Wang, Li; Xu, Huiren; Song, Yilin; Luo, Jinping; Xu, Shengwei; Zhang, Song; Liu, Juntao; Cai, Xinxia

    2015-01-01

    Vesicular exocytosis is ubiquitous, but it is difficult to detect within the cells' communication mechanism. For this purpose, a 2 μm ultramicrodic carbon fiber electrode was fabricated in this work based on electrodeposition with over-oxidized polypyrrole nanoparticle (PPyox-CFE), which was applied successfully for real-time monitoring of quantal exocytosis from individual pheochromocytoma (PC12) cells. PPyox-CFE was evaluated by dopamine (DA) solutions through cyclic voltammetry and amperometry electrochemical methods, and results revealed that PPyox-CFE improved the detection limit of DA. In particular, the sensitivity of DA was improved to 24.55 μA·μM−1·μm−2 using the PPyox-CFE. The ultramicrodic electrode combined with the patch-clamp system was used to detect vesicular exocytosis of DA from individual PC12 cells with 60 mM K+ stimulation. A total of 287 spikes released from 7 PC12 cells were statistically analyzed. The current amplitude (Imax) and the released charge (Q) of the amperometric spikes from the DA release by a stimulated PC12 cell is 45.1 ± 12.5 pA and 0.18 ± 0.04 pC, respectively. Furthermore, on average ∼562,000 molecules were released in each vesicular exocytosis. PPyox-CFE, with its capability of detecting vesicular exocytosis, has potential application in neuron communication research. PMID:25569759

  12. Classification of Spanish white wines using their electrophoretic profiles obtained by capillary zone electrophoresis with amperometric detection.

    Science.gov (United States)

    Arribas, Alberto Sánchez; Martínez-Fernández, Marta; Moreno, Mónica; Bermejo, Esperanza; Zapardiel, Antonio; Chicharro, Manuel

    2014-06-01

    A method was developed for the simultaneous detection of eight polyphenols (t-resveratrol, (+)-catechin, quercetin and p-coumaric, caffeic, sinapic, ferulic, and gallic acids) by CZE with electrochemical detection. Separation of these polyphenols was achieved within 25 min using a 200 mM borate buffer (pH 9.4) containing 10% methanol as separation electrolyte. Amperometric detection of polyphenols was carried out with a glassy carbon electrode (GCE) modified with a multiwalled carbon nanotubes (CNT) layer obtained from a dispersion of CNT in polyethylenimine. The excellent electrochemical properties of this modified electrode allowed the detection and quantification of the selected polyphenols in white wines without any pretreatment step, showing remarkable signal stability despite the presence of potential fouling substances in wine. The electrophoretic profiles of white wines, obtained using this methodology, have proven to be useful for the classification of these wines by means of chemometric multivariate techniques. Principal component analysis and discriminant analysis allowed accurate classification of wine samples on the basis of their grape varietal (verdejo and airén) using the information contained in selected zones of the electropherogram. The utility of the proposed CZE methodology based on the electrochemical response of CNT-modified electrodes appears to be promising in the field of wine industry and it is expected to be successfully extended to classification of a wider range of wines made of other grape varietals. © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  13. Carbon Fiber Ultramicrodic Electrode Electrodeposited with Over-Oxidized Polypyrrole for Amperometric Detection of Vesicular Exocytosis from Pheochromocytoma Cell

    Directory of Open Access Journals (Sweden)

    Li Wang

    2015-01-01

    Full Text Available Vesicular exocytosis is ubiquitous, but it is difficult to detect within the cells’ communication mechanism. For this purpose, a 2 µm ultramicrodic carbon fiber electrode was fabricated in this work based on electrodeposition with over-oxidized polypyrrole nanoparticle (PPyox-CFE, which was applied successfully for real-time monitoring of quantal exocytosis from individual pheochromocytoma (PC12 cells. PPyox-CFE was evaluated by dopamine (DA solutions through cyclic voltammetry and amperometry electrochemical methods, and results revealed that PPyox-CFE improved the detection limit of DA. In particular, the sensitivity of DA was improved to 24.55 µA·µM−1·µm−2 using the PPyox-CFE. The ultramicrodic electrode combined with the patch-clamp system was used to detect vesicular exocytosis of DA from individual PC12 cells with 60 mM K+ stimulation. A total of 287 spikes released from 7 PC12 cells were statistically analyzed. The current amplitude (Imax and the released charge (Q of the amperometric spikes from the DA release by a stimulated PC12 cell is 45.1 ± 12.5 pA and 0.18 ± 0.04 pC, respectively. Furthermore, on average ~562,000 molecules were released in each vesicular exocytosis. PPyox-CFE, with its capability of detecting vesicular exocytosis, has potential application in neuron communication research.

  14. Determination of human serum semicarbazide-sensitive amine oxidase activity via flow injection analysis with fluorescence detection after online derivatization of the enzymatically produced benzaldehyde with 1,2-diaminoanthraquinone.

    Science.gov (United States)

    El-Maghrabey, Mahmoud H; Kishikawa, Naoya; Ohyama, Kaname; Imazato, Takahiro; Ueki, Yukitaka; Kuroda, Naotaka

    2015-06-30

    A fast, simple, and sensitive flow injection analysis method was developed for the measurement of semicarbazide-sensitive amine oxidase (SSAO) activity in human serum. Benzaldehyde, generated by the action of SSAO after incubation of serum with benzylamine, was derivatized with a novel aromatic aldehyde-specific reagent (1,2-diaminoanthraquinone) and the fluorescent product was measured by fluorescence detection at excitation and emission wavelengths of 390 and 570nm, respectively. Serum SSAO activity was defined as benzaldehyde (nmol) formed per milliliter serum per hour. The method was linear over SSAO activity of 0.2-150.0nmolmL(-1)h(-1) with a detection limit of 0.06nmolmL(-1)h(-1). The %RSD of intra-day and inter-day precision did not exceed 9.4% and the accuracy ranged from -6.5 to -0.6%. The method was applied for the determination of the serum SSAO activity in healthy controls (C, n=24) and diabetes mellitus patients (DM, n=18). It was demonstrated that the activity (mean±SE) of SSAO in diabetics sera was significantly higher than that in healthy subjects' ones (DM; 73.3±1.8nmolmL(-1)h(-1)vs C; 58.9±2.2nmolmL(-1)h(-1), P<0.01).

  15. Detection of Benzoic Acid by an Amperometric Inhibitor Biosensor Based on Mushroom Tissue Homogenate

    Directory of Open Access Journals (Sweden)

    Mustafa Kemal Sezgintürk

    2005-01-01

    Full Text Available An amperometric benzoic acid-sensing inhibitor biosensor was prepared by immobilizing mushroom (Agaricus bisporus tissue homogenate on a Clark-type oxygen electrode. The effects of the quantity of mushroom tissue homogenate, the quantity of gelatin and the effect of the crosslinking agent glutaraldehyde percent on the biosensor were studied. The optimum concentration of phenol used as substrate was 200 μM. The bioanalytical properties of the proposed biosensor, such as dependence of the biosensor response on the pH value and the temperature, were investigated. The biosensor responded linearly to benzoic acid in a concentration range of 25–100 μM. Standard deviation (s.d. was ±0.49 μM for 7 successive determinations at a concentration of 75 μM. The inhibitor biosensor based on mushroom tissue homogenate was applied for the determination of benzoic acid in fizzy lemonade, some fruits and groundwater samples. Results were compared to those obtained using AOAC method, showing a good agreement.

  16. Cleanup and analysis of sugar phosphates in biological extracts by using solid phase extraction and anion-exchange chromatography with pulsed amperometric detection

    DEFF Research Database (Denmark)

    Smith, Hans Peter; Cohen, A.; Buttler, T.

    1998-01-01

    A cleanup method based on anion-exchange solid-phase extraction (SPE) was developed to render biological extracts suitable for the analysis of hexose phosphates with a modified anion-exchange chromatography method and pulsed amperometric detection. The method was applied to cell extracts of Sacch......A cleanup method based on anion-exchange solid-phase extraction (SPE) was developed to render biological extracts suitable for the analysis of hexose phosphates with a modified anion-exchange chromatography method and pulsed amperometric detection. The method was applied to cell extracts...... of Saccharomyces cerevisiae obtained by using cold methanol as quenching agent and chloroform as extraction solvent. It was shown that pretreatment of the cell extract with SPE markedly improved the quality of the liquid chromatography analysis with recoveries of the sugar phosphates close to 100%. Furthermore...

  17. Detection of Waterborne and Airborne Formaldehyde: From Amperometric Chemosensing to a Visual Biosensor Based on Alcohol Oxidase

    Directory of Open Access Journals (Sweden)

    Sasi Sigawi

    2014-02-01

    Full Text Available A laboratory prototype of a microcomputer-based analyzer was developed for quantitative determination of formaldehyde in liquid samples, based on catalytic chemosensing elements. It was shown that selectivity for the target analyte could be increased by modulating the working electrode potential. Analytical parameters of three variants of the amperometric analyzer that differed in the chemical structure/configuration of the working electrode were studied. The constructed analyzer was tested on wastewater solutions that contained formaldehyde. A simple low-cost biosensor was developed for semi-quantitative detection of airborne formaldehyde in concentrations exceeding the threshold level. This biosensor is based on a change in the color of a solution that contains a mixture of alcohol oxidase from the yeast Hansenula polymorpha, horseradish peroxidase and a chromogen, following exposure to airborne formaldehyde. The solution is enclosed within a membrane device, which is permeable to formaldehyde vapors. The most efficient and sensitive biosensor for detecting formaldehyde was the one that contained alcohol oxidase with an activity of 1.2 U·mL−1. The biosensor requires no special instrumentation and enables rapid visual detection of airborne formaldehyde at concentrations, which are hazardous to human health.

  18. Uncertainty contributions to the measurement of dissolved Co, Fe, Pb and V in seawater using flow injection with solid phase preconcentration and detection by collision/reaction cell-quadrupole ICP-MS.

    Science.gov (United States)

    Clough, Robert; Sela, Hagit; Milne, Angela; Lohan, Maeve C; Tokalioglu, Serife; Worsfold, Paul J

    2015-02-01

    A flow injection manifold incorporating a solid phase chelating resin (Toyopearl AF-Chelate-650) is reported for the preconcentration of dissolved metals from seawater, with a focus on investigating the effect of the loading pH, wash solution composition and wash time. Cobalt, iron, lead and vanadium have been used as target analytes with contrasting oceanographic behaviour. Quadrupole ICP-MS has been used for detection to make the approach accessible to most laboratories and a collision/reaction cell has been incorporated to minimise polyatomic interferences. Results for the seawater CRM NASS-6 and two GEOTRACES reference materials were in good agreement with the certified/consensus values, demonstrating the suitability of the approach for the determination of trace metals in seawater. The experimental design used allowed a thorough investigation of the uncertainty contribution from each method parameter to the overall expanded uncertainty of the measurement. The results showed that the parameters making the largest contributions were the precision of the peak area measurement and the uncertainty associated with the slope of the calibration curve. Therefore, these are the critical parameters that should be targeted in order to reduce the overall measurement uncertainty. For iron, the wash blank also gave a measureable contribution.

  19. Development of an analytical method for yam saponins using HPLC with pulsed amperometric detection at different column temperatures.

    Science.gov (United States)

    Kwon, Ha-Jeong; Choi, Seung-Hee; Yoo, Chang-Seon; Choi, Hwa-Young; Lee, Soo-Eon; Park, Yong-Duk

    2013-02-01

    Yam saponins (dioscin, gracillin, protodioscin, and protogracillin) were analyzed with three different C18 columns at incremental column temperatures from 15 to 45°C to investigate the effect of temperature on the retention and resolution of yam saponins. At low temperature, yam saponins showed decreased retention times and improved resolutions in the C18 columns. In the Kinetex C18 column at 15°C, the four saponins achieved baseline separation (Rs > 1.5) within 30 min. Pulsed amperometric detection was used to identify saponins with high sensitivity. The limits of detection and quantification of saponins were 0.11-0.31 and 0.33-0.95 ng, respectively. The correlation coefficients ranged 0.9986-1.0000. Intra- and inter-day precisions were yam foods were determined without sample purification or concentration. Among the ten commercial yam foods investigated, only three showed significant saponin contents. © 2012 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  20. Highly sensitive transient isotachophoresis sample stacking coupling with capillary electrophoresis-amperometric detection for analysis of doping substances.

    Science.gov (United States)

    Zheng, Lihui; Zhang, Lan; Tong, Ping; Zheng, Xinyu; Chi, Yuwu; Chen, Guonan

    2010-06-15

    A simple and effective method of capillary electrophoresis-amperometric detection (CE-AD) coupled with transient isotachophoresis (tITP) was developed for the trace determination of doping substances. Compared with the conventional capillary electrophoresis method, the maximum enhancement factor in terms of peak heights was up to 5500-fold when the tITP technique was adopted. Under the optimum conditions, the detection limit (S/N=3) for methylephedrine (MDP), celiprolol (CEL), sotalol (SOT) and indapamide (IDP) were 4.2 x 10(-14), 6.3 x 10(-13), 5.8 x 10(-14) and 9.5 x 10(-13)molL(-1), respectively. The RSDs of four analytes were 1.0-2.3% for migration time and 2.6-3.8% for peak current, respectively. The proposed method was successfully applied to determine the contents of SOT and IDP in real urine sample, and the excretion curve of IDP within 48h was also investigated. The recoveries of the four doping in urine ranged from 90.0 to 102%.

  1. Amperometric detection of carbohydrates based on the glassy carbon electrode modified with gold nano-flake layer

    Directory of Open Access Journals (Sweden)

    Huy Du Nguyen

    2015-09-01

    Full Text Available An electro-deposition approach was established to incorporate the gold nano-flakes onto the glassy carbon electrode in electrochemical cells (nano-Au/GC/ECCs. Using pulsed amperometric detection (PAD without any gold oxidation for cleaning (non-oxidative PAD, the nano-Au/GC/ECCs were able to maintain their activity for oxidizing of carbohydrates in a normal alkaline medium. The reproducibility of peak area was about 2 relative standard deviation (RSD,% for 6 consecutive injections. A dynamic range of carbohydrates was obtained over a concentration range of 5–80 mg L−1 and the limits of detection (LOD were of 2 mg L−1 for fructose and lactose and 1 mg L−1 for glucose and galactose. Moreover, the nano-Au/GC/ECC using the non-oxidative PAD was able to combine with the internal standard method for determination of lactose in fresh cow milk sample.

  2. Fast Determination of Clenbuterol and Salbutamol in Feed and Meat Products Based on Miniaturized Capillary Electrophoresis with Amperometric Detection

    Institute of Scientific and Technical Information of China (English)

    CHU Qing-Cui; GENG Cheng-Huai; ZHOU Hui; YE Jian-Nong

    2007-01-01

    The fast separation capability of a novel miniaturized capillary electrophoresis with an amperometric detection (μCE-AD) system was demonstrated by determining clenbuterol and salbutamol in real samples.The effects of several factors such as the acidity and concentration of the running buffer,the separation voltage,the applied potential and the injection time on CE-AD were examined and optimized.Under the optimum conditions,the two β-agonists could be baseline separated within 60 s at a separation voltage of 2 kV in a 90 mmol/L H3BO3-Na2B4O7 running buffer (pH 7.4),which was not interfered by ascorbic acid and uric acid.Highly linear response was obtained for above compounds over three orders of magnitude with detection limits ranging from 1.20 × 10-7 to 6.50× 10-8 mol/L (S/N=3).This method was successfully used in the analysis of feed and meat products with relatively simple extraction procedures.

  3. Flow Injection will be 25 years

    DEFF Research Database (Denmark)

    Hansen, Elo Harald

    1999-01-01

    The article is a brief review of the first 25 years of Flow Injection Analysis (FIA), that is, from its conception and early development in the mid-70'es at the Department of Chemistry at DTU, yet it is particularly discussing why this analytical concept has had the impact that the ensuing 10...

  4. The Three Generations of Flow Injection Analysis

    DEFF Research Database (Denmark)

    Hansen, Elo Harald; Wang, Jianhua

    2004-01-01

    The characteristics of the three generations of flow injection analysis, that is, FIA, sequential injection analysis (SIA), and bead injection-lab-on-valve (BI-LOV), are briefly outlined, their individual advantages and shortcomings are discussed, and selected practical applications are presented....

  5. Flow Injection Analysis in Industrial Biotechnology

    DEFF Research Database (Denmark)

    Hansen, Elo Harald; Miró, Manuel

    2009-01-01

    Flow injection analysis (FIA) is an analytical chemical continuous-flow (CF) method which in contrast to traditional CF-procedures does not rely on complete physical mixing (homogenisation) of the sample and the reagent(s) or on attaining chemical equilibria of the chemical reactions involved. Ex...

  6. Carbon Nanotube-Plasma Polymer-Based Amperometric Biosensors: Enzyme-Friendly Platform for Ultrasensitive Glucose Detection

    Science.gov (United States)

    Muguruma, Hitoshi; Matsui, Yasunori; Shibayama, Yu

    2007-09-01

    An amperometric enzyme biosensor fabricated with carbon nanotubes (CNTs) and plasma-polymerized thin films (PPFs) is reported. A mixture of the enzyme glucose oxidase (GOD) and a CNT film is sandwiched with 10-nm-thick acetonitrile PPFs. Under PPF layer was deposited onto a sputtered gold electrode. To facilitate the electrochemical communication between the CNT layer and GOD, CNT was treated with oxygen plasma. The device with single-walled CNTs showed a sensitivity higher than that of multiwalled CNTs. The glucose biosensor showed ultrasensitivity (a sensitivity of 40 μA mM-1 cm-2, a correlation coefficient of 0.992, a linear response range of 0.025-1.9 mM, a detection limit of 6.2 μM at S/N = 3, +0.8 V vs Ag/AgCl), and a rapid response (< 4 s in reaching 95% of maximum response). This high performance is attributed to the fact that CNTs have excellent electrocatalytic activity and enhance electron transfer, and that PPFs and/or the plasma process for CNTs are the enzyme-friendly platform, i.e., a suitable design of the interface between GOD and CNTs.

  7. Flow Injection and Atomic Absorption Spectrometry (FI-AAS) -

    DEFF Research Database (Denmark)

    Hansen, Elo Harald

    1996-01-01

    One of the advantages of the flow injection (FI) concept is that it is compatible with virtually all detection techniques. Being a versatile vehicle for enhancing the performance of the individual detection devices, the most spectacular results have possibly been obtained in conjunction with atomic...... the point of sample injection/introduction to the point of detection. Hence, in FI-fAAS this feature allows not only to obtain improved repeatability but also improved accuracy, and because the wash to sample ratio is high it permits the handling of samples with elevated salt contents - which...

  8. Determination of neomycin sulfate and impurities using high-performance anion-exchange chromatography with integrated pulsed amperometric detection.

    Science.gov (United States)

    Hanko, Valoran P; Rohrer, Jeffrey S

    2007-01-01

    Neomycin B is one of a class of aminoglycoside antibiotics that lack a good chromophore, and is therefore difficult to determine using reversed-phase HPLC with absorbance detection. This is especially true for determining the quantity of each impurity. We show that neomycin sulfate and its major impurities, including neamine (neomycin A), can be separated on a strong anion-exchange column using a weak potassium hydroxide eluent (2.40 mM) at a column temperature of 30 degrees C, and directly detected by integrated pulsed amperometric detection (IPAD). The resolution (United States Pharmacopeia (USP) definition) between neomycin B and the closest major impurity ranged from 6.56 and 7.45 over 10 days of consecutive analysis (7.24+/-0.10, n=836 injections). Due to the difficulty of producing weak hydroxide eluents of the required purity (i.e. carbonate-free), this method depends on automatic eluent generation to ensure method ruggedness. This method exhibited good long-term (10 days, 822 injections) retention time stability with a R.S.D. of 0.6%. Peak area R.S.D. (10 microM) was 1.3%. Method robustness was evaluated by intentionally varying the flow rate, eluent concentration, column temperature, and column. The spike recoveries of neomycin B from extractions of three different topical ointments and cream formulations ranged from 95 to 100%. The measured concentration of neomycin B in these formulations ranged from 119 to 154% of the label concentration. The R.S.D. for the measured concentration of one of the formulations tested over three separate days, n=11 extracts, was 3.2%. Based on the results of these evaluations, we believe this method can be used for neomycin sulfate identity, assay, and purity.

  9. Double injection/single detection asymmetric flow injection manifold for spectrophotometric determination of ascorbic acid and uric acid: Selection the optimal conditions by MCDM approach based on different criteria weighting methods

    Science.gov (United States)

    Boroumand, Samira; Chamjangali, Mansour Arab; Bagherian, Ghadamali

    2017-03-01

    A simple and sensitive double injection/single detector flow injection analysis (FIA) method is proposed for the simultaneous kinetic determination of ascorbic acid (AA) and uric acid (UA). This method is based upon the difference between the rates of the AA and UA reactions with Fe3 + in the presence of 1, 10-phenanthroline (phen). The absorbance of Fe2 +/1, 10-phenanthroline (Fe-phen) complex obtained as the product was measured spectrophotometrically at 510 nm. To reach a good accuracy in the differential kinetic determination via the mathematical manipulations of the transient signals, different criteria were considered in the selection of the optimum conditions. The multi criteria decision making (MCDM) approach was applied for the selection of the optimum conditions. The importance weights of the evaluation criteria were determined using the analytic hierarchy process, entropy method, and compromised weighting (CW). The experimental conditions (alternatives) were ranked by the technique for order preference by similarity to an ideal solution. Under the selected optimum conditions, the obtained analytical signals were linear in the ranges of 0.50-5.00 and 0.50-4.00 mg L- 1 for AA and UA, respectively. The 3σ detection limits were 0.07 mg L- 1 for AA and 0.12 mg L- 1 for UA. The relative standard deviations for four replicate determinations of AA and UA were 2.03% and 3.30% respectively. The method was also applied for the analysis of analytes in the blood serum, Vitamine C tablets, and tap water with satisfactory results.

  10. A disposable amperometric dual-sensor for the detection of hemoglobin and glycated hemoglobin in a finger prick blood sample.

    Science.gov (United States)

    Moon, Jong-Min; Kim, Dong-Min; Kim, Moo Hyun; Han, Jin-Yeong; Jung, Dong-Keun; Shim, Yoon-Bo

    2017-05-15

    A disposable microfluidic amperometric dual-sensor was developed for the detection of glycated hemoglobin (HbA1C) and total hemoglobin (Hb), separately, in a finger prick blood sample. The accurate level of total Hb was determined through the measurements of the cathodic currents of total Hb catalyzed by a toluidine blue O (TBO)-modified working electrode. Subsequently, after washing unbound Hb in the fluidic channel of dual sensor with PBS, the cathodic current by only HbA1C captured on aptamer was monitored using another aptamer/TBO-modified working electrode in the channel. To modify the sensor probe, poly(2,2´:5´,5″-terthiophene-3´-p-benzoic acid) and a multi-wall carbon nanotube (MWCNT) composite layer (pTBA@MWCNT) was electropolymerized on a screen printed carbon electrode (SPCE), followed by immobilization of TBO for the total Hb probe and aptamer/TBO for the HbA1C probe, respectively. The characterization of each sensor surface was performed using cyclic voltammetry (CV), electrochemical impedance spectroscopy (EIS), X-ray photoelectron spectroscopy (XPS), quartz crystal microbalance (QCM), field-emission scanning electron microscopy (FE-SEM), and transmission electron microscopy (TEM). The experimental conditions affecting the analytical signal were optimized in terms of the amount of TBO, pH, temperature, binding time, applied potential, and the content ratio of monomer and MWCNT. The dynamic ranges of Hb and HbA1C were from 0.1 to 10µM and from 0.006 to 0.74µM, with detection limits of 82(±4.2)nM and 3.7(±0.8)nM, respectively. The reliability of the proposed microfluidic dual-sensor for a finger prick blood sample (1µL) was evaluated in parallel with a conventional method (HPLC) for point-of-care analysis.

  11. An Inexpensive Detector for Absorbance Measurements in Flow-Injection Analysis

    Science.gov (United States)

    Hauser, Peter C.; Cates, Norman E.

    1996-02-01

    A photometric transducer for peak detection in flow-injection analysis is described. It relies on a light-emitting diode as the light source and a photodiode as the detector. A logarithmic amplifier is used in order to emulate Beer-Lambert's Law and to directly obtain absorbance readings. The performance has been tested with two commonly employed flow-injection procedures, but the device should be suitable for most methods that may be used in the teaching lab.

  12. Simultaneous detection of two breast cancer-related miRNAs in tumor tissues using p19-based disposable amperometric magnetobiosensing platforms.

    Science.gov (United States)

    Torrente-Rodríguez, R M; Campuzano, S; López-Hernández, E; Montiel, V Ruiz-Valdepeñas; Barderas, R; Granados, R; Sánchez-Puelles, J M; Pingarrón, J M

    2015-04-15

    A novel magnetobiosensing approach for the rapid and simultaneous detection of two breast cancer-related miRs (miR-21 and miR-205) is reported. It involves the use of antimiR-21 and antimiR-205 specific probes, chitin-modified magnetic beads (Chitin-MBs), the p19 viral protein as capture bioreceptor and amperometric detection with the H2O2/hydroquinone (HQ) system at dual screen-printed carbon electrodes (SPdCEs). The use of SPdCEs allows the simultaneous independent amperometric readout for each target miR to be measured. The magnetosensor exhibited sensitive and selective detection with dynamic ranges from 2.0 to 10.0nM and detection limits of 0.6nM (6fmol) for both target miRs without any amplification step in less than 2h. The usefulness of the approach was evaluated by detecting the endogenous levels of both target miRs in total RNA (RNAt) extracted from metastatic breast cancer cell lines and human tissues.

  13. Carbon film resistor electrode for amperometric determination of acetaminophen in pharmaceutical formulations.

    Science.gov (United States)

    Felix, Fabiana S; Brett, Christopher M A; Angnes, Lúcio

    2007-04-11

    Flow injection analysis (FIA) with amperometric detection was employed for acetaminophen quantification in pharmaceutical formulations using a carbon film resistor electrode. This sensor exhibited sharp and reproducible current peaks for acetaminophen without chemical modification of its surface. A wide linear working range (8.0x10(-7) to 5.0x10(-4) mol L(-1)) in phosphate buffer solution as well as high sensitivity (0.143 A mol(-1) L cm(-2)) and low submicromolar detection limit (1.36x10(-7) mol L(-1)) were achieved. The repeatability (R.S.D. for 10 successive injections of 5.0x10(-6) and 5.0x10(-5) mol L(-1) acetaminophen solutions) was 3.1 and 1.3%, respectively, without any memory effect between injections. The new procedure was applied to the analyses of commercial pharmaceutical products and the results were in good agreement with those obtained utilizing a spectrophotometric method. Consequently, this amperometric method has been shown to be very suitable for quality control analyses and other applications with similar requirements.

  14. Preparation of metal nanoband microelectrode on poly(dimethylsiloxane) for chip-based amperometric detection

    Energy Technology Data Exchange (ETDEWEB)

    Chen Shaopeng; Wu Jian; Yu Xiaodong [Key Laboratory of Analytical Chemistry for Life Science, Ministry of Education of China, School of Chemistry and Chemical Engineering, Nanjing University, Nanjing 210093 (China); Xu Jingjuan, E-mail: xujj@nju.edu.cn [Key Laboratory of Analytical Chemistry for Life Science, Ministry of Education of China, School of Chemistry and Chemical Engineering, Nanjing University, Nanjing 210093 (China); Chen Hongyuan [Key Laboratory of Analytical Chemistry for Life Science, Ministry of Education of China, School of Chemistry and Chemical Engineering, Nanjing University, Nanjing 210093 (China)

    2010-04-30

    We proposed herein a novel approach for fabricating nanoband microelectrodes for electrochemical detection on an electrophoresis microchip. The metal films were first obtained via region-selective electroless deposition of gold or copper films on PDMS substrates by selective region plasma oxidation through shadow masking. Both metal films show uniform surfaces with the thickness at the level of 100 nm. By casting another PDMS layer on the metal films, the cross section of the sandwich structures can be used as nanoband microelectrodes, which can be renewed just by cutting. These nanoband microelectrodes are successfully used as electrochemical detectors in microchip electrophoresis for the detection of amino acids, proteins and neurotransmitter molecules. Moreover, integrating an Au-Cu double-metal detector with a double-channel electrophoresis system, we can easily distinguish electroactive amino acids from that of non-electroactive amino acids.

  15. Electrophoretically deposited multiwalled carbon nanotube based amperometric genosensor for E.coli detection

    Science.gov (United States)

    Bhardwaj, Hema; Solanki, Shipra; Sumana, Gajjala

    2016-04-01

    This work reports on a sensitive and selective genosensor fabrication method for Escherichia coli (E.coli) detection. The functionalized multiwalled carbon nanotubes (MWCNT) synthesized via chemical vapour deposition have been deposited electrophoretically onto indium tin oxide coated glass surface and have been utilized as matrices for the covalent immobilization of E.coli specific probe oligonucleotide that was identified from the 16s rRNA coding region of the E.coli genome. This fabricated functionalized MWCNT based platform sought to provide improved fundamental characteristics to electrode interface in terms of electro-active surface area and diffusion coefficient. Electrochemical cyclic voltammetry revealed that this genosensor exhibits a linear response to complementary DNA in the concentration range of 10-7 to 10-12 M with a detection limit of 1×10-12 M.

  16. Ternary surface monolayers for ultrasensitive (zeptomole) amperometric detection of nucleic acid hybridization without signal amplification.

    Science.gov (United States)

    Wu, Jie; Campuzano, Susana; Halford, Colin; Haake, David A; Wang, Joseph

    2010-11-01

    A ternary surface monolayer, consisting of coassembled thiolated capture probe, mercaptohexanol and dithiothreitol, is shown to offer dramatic improvements in the signal-to-noise characteristics of electrochemical DNA hybridization biosensors based on common self-assembled monolayers. Remarkably low detection limits down to 40 zmol (in 4 μL samples) as well as only 1 CFU Escherichia coli per sensor are thus obtained without any additional amplification step in connection to the commonly used horseradish peroxidase/3,3',5,5'-tetramethylbenzidine system. Such dramatic improvements in the detection limits (compared to those of common binary alkanethiol interfaces and to those of most electrochemical DNA sensing strategies without target or signal amplification) are attributed primarily to the remarkably higher resistance to nonspecific adsorption. This reflects the highly compact layer (with lower pinhole density) produced by the coupling of the cyclic- and linear-configuration "backfillers" that leads to a remarkably low background noise even in the presence of complex sample matrixes. A wide range of surface compositions have been investigated, and the ternary mixed monolayer has been systematically optimized. Detailed impedance spectroscopy and cyclic voltammetric studies shed useful insights into the surface coverage. The impressive sensitivity and high specificity of the simple developed methodology indicate great promise for a wide range of nucleic acid testing, including clinical diagnostics, biothreat detection, food safety, and forensic analysis.

  17. Immobilized Bioluminescent Reagents in Flow Injection Analysis.

    Science.gov (United States)

    Nabi, Abdul

    Available from UMI in association with The British Library. Bioluminescent reactions exhibits two important characteristics from an analytical viewpoint; they are selective and highly sensitive. Furthermore, bioluminescent emissions are easily measured with a simple flow-through detector based on a photomultiplier tube and the rapid and reproducible mixing of sample and expensive reagent is best achieved by a flow injection manifold. The two most important bioluminescent systems are the enzyme (luciferase)/substrate (luciferin) combinations extracted from fireflies (Photinus pyralis) and marine bacteria (Virio harveyi) which requires ATP and NAD(P)H respectively as cofactors. Reactions that generate or consume these cofactors can also be coupled to the bioluminescent reaction to provide assays for a wide range of clinically important species. A flow injection manifold for the study of bioluminescent reactions is described, as are procedures for the extraction, purification and immobilization of firefly and bacterial luciferase and oxidoreductase. Results are presented for the determination of ATP using firefly system and the determination of other enzymes and substrates participating in ATP-converting reactions e.g. creatine kinase, ATP-sulphurylase, pyruvate kinase, creatine phosphate, pyrophosphate and phophoenolypyruvate. Similarly results are presented for the determination of NAD(P)H, FMN, FMNH_2 and several dehydrogenases which produce NAD(P)H and their substrates, e.g. alcohol, L-lactate, L-malate, L-glutamate, Glucose-6-phosphate and primary bile acid.

  18. An integrated amperometric biosensor for the determination of lactose in milk and dairy products.

    Science.gov (United States)

    Conzuelo, F; Gamella, M; Campuzano, S; Ruiz, M A; Reviejo, A J; Pingarrón, J M

    2010-06-23

    An integrated amperometric biosensor for the determination of lactose is reported. The bioelectrode design is based on the use of a 3-mercaptopropionic acid (MPA) self-assembled monolayer (SAM)-modified gold electrode on which the enzymes beta-galactosidase (beta-Gal), glucose oxidase (GOD), peroxidase (HRP) and the mediator tetrathiafulvalene (TTF) are coimmobilized by a dialysis membrane. beta-Gal catalyzes the hydrolysis of lactose, and the produced glucose is catalytically oxidized to gluconic acid and H(2)O(2), which is reduced in the presence of HRP. This enzyme reaction is mediated by TTF, and the reduction of TTF(+) at 0.00 V (vs Ag/AgCl) gives rise to an amperometric signal proportional to the lactose concentration. The biosensor exhibits a good repeatability of the measurement carried out with the same biosensor, a good reproducibility of the responses obtained with different biosensors and a useful lifetime of 28 days. A linear calibration plot was obtained for lactose over the 1.5 x 10(-6) to 1.2 x 10(-4) M concentration range, with a limit of detection of 4.6 x 10(-7) M. The effect of potential interferents (sucrose, lactulose, fructose, arabinose, maltose, galactose, glucose and uric and ascorbic acids) on the biosensor response was evaluated. Furthermore, the bioelectrode exhibits a suitable performance in flow-injection systems in connection with amperometric detection. The developed biosensor was applied to the determination of lactose in milk and other foodstuffs (chocolate, butter, margarine, yogurt, cheese and mayonnaise), and the results obtained were validated by comparison with those provided by using a commercial enzyme test kit.

  19. Simple and clean determination of tetracyclines by flow injection analysis

    Science.gov (United States)

    Rodríguez, Michael Pérez; Pezza, Helena Redigolo; Pezza, Leonardo

    2016-01-01

    An environmentally reliable analytical methodology was developed for direct quantification of tetracycline (TC) and oxytetracycline (OTC) using continuous flow injection analysis with spectrophotometric detection. The method is based on the diazo coupling reaction between the tetracyclines and diazotized sulfanilic acid in a basic medium, resulting in the formation of an intense orange azo compound that presents maximum absorption at 434 nm. Experimental design was used to optimize the analytical conditions. The proposed technique was validated over the concentration range of 1 to 40 μg mL- 1, and was successfully applied to samples of commercial veterinary pharmaceuticals. The detection (LOD) and quantification (LOQ) limits were 0.40 and 1.35 μg mL- 1, respectively. The samples were also analyzed by an HPLC method, and the results showed agreement with the proposed technique. The new flow injection method can be immediately used for quality control purposes in the pharmaceutical industry, facilitating monitoring in real time during the production processes of tetracycline formulations for veterinary use.

  20. A Facile Electrochemical Preparation of Reduced Graphene Oxide@Polydopamine Composite: A Novel Electrochemical Sensing Platform for Amperometric Detection of Chlorpromazine

    Science.gov (United States)

    Palanisamy, Selvakumar; Thirumalraj, Balamurugan; Chen, Shen-Ming; Wang, Yi-Ting; Velusamy, Vijayalakshmi; Ramaraj, Sayee Kannan

    2016-09-01

    We report a novel and sensitive amperometric sensor for chlorpromazine (CPZ) based on reduced graphene oxide (RGO) and polydopamine (PDA) composite modified glassy carbon electrode. The RGO@PDA composite was prepared by electrochemical reduction of graphene oxide (GO) with PDA. The RGO@PDA composite modified electrode shows an excellent electro-oxidation behavior to CPZ when compared with other modified electrodes such as GO, RGO and GO@PDA. Amperometric i-t method was used for the determination of CPZ. Amperometry result shows that the RGO@PDA composite detects CPZ in a linear range from 0.03 to 967.6 μM. The sensor exhibits a low detection limit of 0.0018 μM with the analytical sensitivity of 3.63 ± 0.3 μAμM-1 cm-2. The RGO@PDA composite shows its high selectivity towards CPZ in the presence of potentially interfering drugs such as metronidazole, phenobarbital, chlorpheniramine maleate, pyridoxine and riboflavin. In addition, the fabricated RGO@PDA modified electrode showed an appropriate recovery towards CPZ in the pharmaceutical tablets.

  1. A Facile Electrochemical Preparation of Reduced Graphene Oxide@Polydopamine Composite: A Novel Electrochemical Sensing Platform for Amperometric Detection of Chlorpromazine

    Science.gov (United States)

    Palanisamy, Selvakumar; Thirumalraj, Balamurugan; Chen, Shen-Ming; Wang, Yi-Ting; Velusamy, Vijayalakshmi; Ramaraj, Sayee Kannan

    2016-01-01

    We report a novel and sensitive amperometric sensor for chlorpromazine (CPZ) based on reduced graphene oxide (RGO) and polydopamine (PDA) composite modified glassy carbon electrode. The RGO@PDA composite was prepared by electrochemical reduction of graphene oxide (GO) with PDA. The RGO@PDA composite modified electrode shows an excellent electro-oxidation behavior to CPZ when compared with other modified electrodes such as GO, RGO and GO@PDA. Amperometric i-t method was used for the determination of CPZ. Amperometry result shows that the RGO@PDA composite detects CPZ in a linear range from 0.03 to 967.6 μM. The sensor exhibits a low detection limit of 0.0018 μM with the analytical sensitivity of 3.63 ± 0.3 μAμM–1 cm–2. The RGO@PDA composite shows its high selectivity towards CPZ in the presence of potentially interfering drugs such as metronidazole, phenobarbital, chlorpheniramine maleate, pyridoxine and riboflavin. In addition, the fabricated RGO@PDA modified electrode showed an appropriate recovery towards CPZ in the pharmaceutical tablets. PMID:27650697

  2. Automated resolution of dichlorvos and methylparaoxon pesticide mixtures employing a Flow Injection system with an inhibition electronic tongue.

    Science.gov (United States)

    Valdés-Ramírez, G; Gutiérrez, M; Del Valle, M; Ramírez-Silva, M T; Fournier, D; Marty, J-L

    2009-01-01

    An amperometric biosensor array has been developed to resolve pesticide mixtures of dichlorvos and methylparaoxon. The biosensor array has been used in a Flow Injection system, in order to operate automatically the inhibition procedure. The sensors used were three screen-printed amperometric biosensors that incorporated three different acetylcholinesterase enzymes: the wild type from Electric eel and two different genetically modified enzymes, B1 and B394 mutants, from Drosophila melanogaster. The inhibition response triplet was modelled using an Artificial Neural Network which was trained with mixture solutions that contain dichlorvos from 10(-4) to 0.1 microM and methylparaoxon from 0.001 to 2.5 microM. This system can be considered an inhibition electronic tongue.

  3. Amperometric detection of gold by differential pulse voltammetry using a DNA biosensor

    Institute of Scientific and Technical Information of China (English)

    GAN Ning; WANG Zhiying; XU Weiming; PAN Jianguo

    2007-01-01

    A DNA biosensor with [Ru(DA-bpy)3]Cl2(DA-bpy:4,4'-diamino-2,2'-bipyridine) (RuL) as the electrochemical probe was prepared on pyrolytic graphite electrode (PGE) through the supramolecular interaction between RuL complex and DNA template. Cyclic voltammetry of RuL-DNA film showed a pair of stable and reversible peaks corresponding to the Ru(Ⅲ)/Ru(Ⅱ) redox potential of-0.165 V versus Ag|AgCl in pH 7.4 0.1 mol· L-1 Tris-HCl. The electron transfer was expected across the double-strand DNA by an "electron tunneling" mechanism. When the DNA biosensor was immerged in gold (Ⅲ) buffer solution, the current peak signal (Ⅰ) of the RuL-DNA supramolecular depressed and △Ⅰ was linear in the concentration range of Au ion from 1 × 10-7 to 2 × 10-5 mol·L-1 with a regression coefficient of 0.9879. The detection limit was 5 × 10-8 mol·L-1. The developed procedures were applied to the analysis of synthetic samples of real materials with good sensitivity and selectivity.

  4. Capillary Zone Electrophoresis with Amperometric Detection for Composition Analysis of Laminarin

    Institute of Scientific and Technical Information of China (English)

    王清江; 丁飞; 李辉; 何品刚; 方禹之

    2003-01-01

    The composition of laminartn was firstly determined by analyz-ing its hydrolysis monosaccharides with capillary zone elec.lected opamum conditions, fucose, galactose, glucose, man-nose and xylose, which are hydrolysis products of iaminarin,could be perfectly separated within 20 min and showed signifi-cant current responses at copper electrodes. The linear ranges of fucose, galactose and glucose were from 1.0 × 10-6 to 2.0 ×10-4 mol·L-1, those of mannose and xylose were from 1.0×10-6 to 2.0× 10-4 mol·L-1, and their detect/on limits were at 10-7mol·L-1 level (S/N =3). The molar ratio of fucose,galactose,glucose,mannose and xylose in laminartn was 10.5:2.8:1.0:7.3:3.4 and the purity of this polysaccharide leached by the introduced leaching method was 95.7%. Compared to usual UV-vis and other spectrometric methods, analyzing polysaccharide by this method has some merit sof quickness,low-volume sampling,simple instrumentation,high sensitivity and high reproducibility.

  5. Sensitive flow-injection spectrophotometric analysis of bromopride

    Science.gov (United States)

    Lima, Liliane Spazzapam; Weinert, Patrícia Los; Pezza, Leonardo; Pezza, Helena Redigolo

    2014-12-01

    A flow injection spectrophotometric procedure employing merging zones is proposed for direct bromopride determination in pharmaceutical formulations and biological fluids. The proposed method is based on the reaction between bromopride and p-dimethylaminocinnamaldehyde (p-DAC) in acid medium, in the presence of sodium dodecyl sulfate (SDS), resulting in formation of a violet product (λmax = 565 nm). Experimental design methodologies were used to optimize the experimental conditions. The Beer-Lambert law was obeyed in a bromopride concentration range of 3.63 × 10-7 to 2.90 × 10-5 mol L-1, with a correlation coefficient (r) of 0.9999. The limits of detection and quantification were 1.07 × 10-7 and 3.57 × 10-7 mol L-1, respectively. The proposed method was successfully applied to the determination of bromopride in pharmaceuticals and human urine, and recoveries of the drug from these media were in the ranges 99.6-101.2% and 98.6-102.1%, respectively. This new flow injection procedure does not require any sample pretreatment steps.

  6. Determination of chlorogenic acid by flow injection irreversible biamperometry

    Institute of Scientific and Technical Information of China (English)

    Li Jun Li; Qi Feng Chen; Lai Bo Yu; Zhao Heng Zhong; Jun Feng; Hao Cheng; Hong Xing Kong; Jian Ling Wu

    2007-01-01

    A flow injection irreversible biamperometric method for the determination of chlorogenic acid is described. The proposed method is based on the electrochemical oxidation of chlorogenic acid at pretreated platinum electrode and the reduction of permanganate at another electrode to form an irreversible biamperometric detection system. Under the external potential difference(△E) of 0 V, in the 0.05 mol/L sulfuric acid, chlorogenic acid can be determined over the range 0.8-120 mg/L with a sample measurement frequency of 80 samples/h. The detection limit is 0.18 mg/L. The proposed method exhibits the satisfactory reproducibility with a relative standard derivation (R.S.D.) of 2.21% for 19 successive determinations of 40 mg/L.

  7. Principles and Applications of Flow Injection Analysis in Biosensors

    DEFF Research Database (Denmark)

    Hansen, Elo Harald

    1996-01-01

    In practical applications biosensors are often forced to operate under less than optimal conditions. Because of their construction, and the physical processes and chemical reactions involved in their operation, compromise conditions are frequently required to synchronize all events taking place....... Therefore, and in order to implement functions such as periodic calibration, conditioning and possible regeneration of the biosensor, and, very importantly, to yield the freedom to select the optimum detection means, it is advantageous to use these devices in a flow-through mode, particularly by employing...... the flow injection (FI) approach. The capacity of FI, as offering itself as a complementary facility to augment the performance of biosensors, and in many cases as an attractive alternative, is demonstrated by reference to selected examples, comprising assays based on enzymatic procedures with optical...

  8. Plasma catecholamines in hypertension and pheochromocytoma determined using ion-pair reversed-phase chromatography with amperometric detection: investigation of the separation mechanism and clinical methodology.

    Science.gov (United States)

    Krstulović, A M; Dziedzic, S W; Bertani-Dziedzic, L; DiRico, D E

    1981-11-06

    The retention behavior of catecholamines (CAs) in ion-pair reversed-phase chromatography is examined. From the effects of pH, ionic strength and a secondary ion-pairing reagent (citric acid), under our chromatographic conditions, the retention behavior can be explained by assuming a mixed ion-exchange mechanism with octyl sulfate and citrate, on the column and in the mobile phase, respectively. The developed separation method was applied to the analysis of CAs in plasma samples purified by alumina adsorption and detected amperometrically. This method provides the basis for the determination of the short-term magnitude of CA response to physical and physiological interventions, as well as the baseline CA levels in essential hypertension and pheochromocytoma. The results seen for norepinephrine and epinephrine are consistent with eh funcitonal roles of these CAs as hormones or peripheral transmitters.

  9. Hot-wire amperometric monitoring of flowing streams.

    Science.gov (United States)

    Wang, J; Jasinski, M; Flechsig, G U; Grundler, P; Tian, B

    2000-01-10

    This paper describes the design of a hot-wire electrochemical flow detector, and the advantages accrued from the effects of locally increased temperature, mainly thermally induced convection, upon the amperometric monitoring of flowing streams. A new hydrodynamic modulation voltammetric approach is presented, in which the solution flow rate remains constant while the temperature of the working electrode is modulated. Factors influencing the response, including the flow rate, temperature pulse, or applied potential, have been investigated. The hot-wire operation results also in a significant enhancement of the flow injection amperometric response. The minimal flow rate dependence observed with the heated electrode should benefit the on-line monitoring of streams with fluctuated natural convection, as well as various in-situ remote sensing applications.

  10. Amperometric detection of heavy metal ions in ion pair chromatography at an array of water/nitrobenzene micro interfaces

    Energy Technology Data Exchange (ETDEWEB)

    Wilke, S. [Martin-Luther-Univ. Halle-Wittenberg, Merseburg (Germany). Fachbereich Chemie; Wang, H. [Martin-Luther-Univ. Halle-Wittenberg, Merseburg (Germany). Fachbereich Chemie; Muraczewska, M. [Martin-Luther-Univ. Halle-Wittenberg, Merseburg (Germany). Fachbereich Chemie; Mueller, H. [Martin-Luther-Univ. Halle-Wittenberg, Merseburg (Germany). Fachbereich Chemie

    1996-10-01

    A novel amperometric detector for heavy metal ions has been developed and successfully applied for ion pair chromatography. The detector is based on the electrochemical transfer of the metal ions across an array of water/nitrobenzene micro interfaces. The ion transfer is facilitated by the neutral ionophores methylenebis(diphenylphosphineoxide) and methylenebis(di- phenylphosphinesulfide). More than eight metals are separated in less than 15 min on an RP18 column using octyl sulfonate as ion pair reagent. For the heavy metals, the limits of decision are 19(Pb{sup 2+}), 9(Zn{sup 2+}), 9l (Co{sup 2+}), 8(Cd{sup 2+}) and 1.6(Mn{sup 2+}) {mu}g/L. The applicability of the new method for water samples is demonstrated. (orig.). With 3 figs., 2 tabs.

  11. Micro-flow-injection analysis (μFIA) immunoassay of herbicide residue 2,6-dichlorobenzamide

    DEFF Research Database (Denmark)

    Uthuppu, Basil; Heiskanen, Arto; Kofoed, Dan

    2015-01-01

    As a part of developing new systems for continuously monitoring the presence of pesticides in groundwater, a microfluidic amperometric immunosensor was developed for detecting the herbicide residue 2,6-dichlorobenzamide (BAM) in water. A competitive immunosorbent assay served as the sensing mecha...

  12. [Determination of lead with GFAAS using online flow injection].

    Science.gov (United States)

    Chen, Zhong-Lan

    2007-06-01

    A cheap, rapid and sensitive method for the determination of trace amount of lead in water samples by graphite furnace absorption spectrometry coupled with online flow injection preconcentration with ammonium pyrrolidine dithiocarboxylate chelating cellulose (CC-APDC) was developed. There were six steps in the preconcentration of flow injection: first, 0.15 mL nitric acid was used for a complete elution, which exceeded the volume of the graphite tube, so the 40 mL solution was removed before eluting. Secondly, 40 mL maximum concentration elution solution was added to GFAAS by fixed volume sampling to improve the accuracy. In addition, traditional stopping gas measurement was substituted with small flow gas atomization (30 mL x min(-1), preconcention for 1 min) during the removal of high memory effect for ashing stage in graphite furnace, which develops tail-out phenomenon and makes blank value low and steady. Various parameters affecting the adsorption and elution, such as pH of the solution, eluent concentration, sample flow rate etc, were optimized. If miniflow in atomization step was used, the memory effect in the determination of lead by GFAAS could be removed. The CC-APDC was used for preparation and preconcentration. A good precision (RSD = 1.4%, n = 10), high enrichment factor (15) and sample throughput (50 h) with detection limit 0.12 microg x L(-1) were obtained. This method has been successfully applied to the water sample for lead determination with a recovery of 95%-105%.

  13. Differentiating organically and conventionally grown oregano using ultraperformance liquid chromatography mass spectrometry (UPLC-MS), headspace gas chromatography with flame ionization detection (headspace-GC-FID), and flow injection mass spectrum (FIMS) fingerprints combined with multivariate data analysis.

    Science.gov (United States)

    Gao, Boyan; Qin, Fang; Ding, Tingting; Chen, Yineng; Lu, Weiying; Yu, Liangli Lucy

    2014-08-13

    Ultraperformance liquid chromatography mass spectrometry (UPLC-MS), flow injection mass spectrometry (FIMS), and headspace gas chromatography (headspace-GC) combined with multivariate data analysis techniques were examined and compared in differentiating organically grown oregano from that grown conventionally. It is the first time that headspace-GC fingerprinting technology is reported in differentiating organically and conventionally grown spice samples. The results also indicated that UPLC-MS, FIMS, and headspace-GC-FID fingerprints with OPLS-DA were able to effectively distinguish oreganos under different growing conditions, whereas with PCA, only FIMS fingerprint could differentiate the organically and conventionally grown oregano samples. UPLC fingerprinting provided detailed information about the chemical composition of oregano with a longer analysis time, whereas FIMS finished a sample analysis within 1 min. On the other hand, headspace GC-FID fingerprinting required no sample pretreatment, suggesting its potential as a high-throughput method in distinguishing organically and conventionally grown oregano samples. In addition, chemical components in oregano were identified by their molecular weight using QTOF-MS and headspace-GC-MS.

  14. Evaluation of in-channel amperometric detection using a dual-channel microchip electrophoresis device and a two-electrode potentiostat for reverse polarity separations.

    Science.gov (United States)

    Meneses, Diogenes; Gunasekara, Dulan B; Pichetsurnthorn, Pann; da Silva, José A F; de Abreu, Fabiane C; Lunte, Susan M

    2015-02-01

    In-channel amperometric detection combined with dual-channel microchip electrophoresis is evaluated using a two-electrode isolated potentiostat for reverse polarity separations. The device consists of two separate channels with the working and reference electrodes placed at identical positions relative to the end of the channel, enabling noise subtraction. In previous reports of this configuration, normal polarity and a three-electrode detection system were used. In the two-electrode detection system described here, the electrode in the reference channel acts as both the counter and reference. The effect of electrode placement in the channels on noise and detector response was investigated using nitrite, tyrosine, and hydrogen peroxide as model compounds. The effects of electrode material and size and type of reference electrode on noise and the potential shift of hydrodynamic voltammograms for the model compounds were determined. In addition, the performance of two- and three-electrode configurations using Pt and Ag/AgCl reference electrodes was compared. Although the signal was attenuated with the Pt reference, the noise was also significantly reduced. It was found that lower LOD were obtained for all three compounds with the dual-channel configuration compared to single-channel, in-channel detection. The dual-channel method was then used for the detection of nitrite in a dermal microdialysis sample obtained from a sheep following nitroglycerin administration.

  15. Highly sensitive flow-injection chemiluminescence determination of pyrogallol compounds

    Science.gov (United States)

    Kanwal, Shamsa; Fu, Xiaohong; Su, Xingguang

    2009-12-01

    A highly sensitive flow-injection chemiluminescent method for the direct determination of pyrogallol compounds has been developed. Proposed method is based on the enhanced effect of pyrogallol compounds on the chemiluminescence signals of KMnO 4-H 2O 2 system in slightly alkaline medium. Three important pyrogallol compounds, pyrogallic acid, gallic acid and tannic acid, have been detected by this method, and the possible mechanism of the CL reaction is also discussed. The proposed method is simple, convenient, rapid (60 samples h -1), and sensitive, has a linear range of 8 × 10 -10 mol L -1 to 1 × 10 -5 mol L -1, for pyrogallic acid, with a detection limit of 6 × 10 -11 mol L -1, 4 × 10 -8 mol L -1 to 5 × 10 -3 mol L -1 for gallic acid with a detection limit of 9 × 10 -10 mol L -1, and 8 × 10 -8 mol L -1 to 5 × 10 -2 mol L -1 for tannic acid, with a detection limit of 2 × 10 -9 mol L -1, respectively. The relative standard deviation (RSD, n = 15) was 0.8, 1.1 and 1.3% for 5 × 10 -6 mol L -1 pyrogallic acid, gallic acid and tannic acid, respectively. The proposed method was successfully applied to the determination of pyrogallol compounds in tea and coffee samples.

  16. Amperometric Biosensor Based on Diamine Oxidase/Platinum Nanoparticles/Graphene/Chitosan Modified Screen-Printed Carbon Electrode for Histamine Detection.

    Science.gov (United States)

    Apetrei, Irina Mirela; Apetrei, Constantin

    2016-03-24

    This work describes the development and optimization studies of a novel biosensor employed in the detection and quantification of histamine in freshwater fish samples. The proposed biosensor is based on a modified carbon screen-printed electrode with diamineoxidase, graphene and platinum nanoparticles, which detects the hydrogen peroxide formed by the chemical process biocatalysed by the enzyme diamine oxidase and immobilized onto the nanostructurated surface of the receptor element. The amperometric measurements with the biosensor have been implemented in buffer solution of pH 7.4, applying an optimal low potential of +0.4 V. The novel biosensor shows high sensitivity (0.0631 μA·μM), low detection limit (2.54 × 10(-8) M) and a broad linear domain from 0.1 to 300 μM. The applicability in natural complex samples and the analytical parameters of this enzyme sensor have been performed in the quantification of histamine in freshwater fish. An excellent correlation among results achieved with the developed biosensor and results found with the standard method for all freshwater fish samples has been achieved.

  17. Carbon nanotubes and graphene modified screen-printed carbon electrodes as sensitive sensors for the determination of phytochelatins in plants using liquid chromatography with amperometric detection.

    Science.gov (United States)

    Dago, Àngela; Navarro, Javier; Ariño, Cristina; Díaz-Cruz, José Manuel; Esteban, Miquel

    2015-08-28

    Nanomaterials are of great interest for the development of electrochemical sensors. Multi-walled carbon nanotubes and graphene were used to modify the working electrode surface of different screen-printed carbon electrodes (SPCE) with the aim of improving the sensitivity of the SPCE and comparing it with the conventional glassy carbon electrode. To assay the usability of these sensors, a HPLC methodology with amperometric detection was developed to analyze several phytochelatins in plants of Hordeum vulgare and Glycine max treated with Hg(II) or Cd(II) giving detection limits in the low μmolL(-1) range. Phytochelatins are low molecular weight peptides with the general structure γ-(Glu-Cys)n-Gly (n=2-5) which are synthesized in plants in the presence of heavy metal ions. These compounds can chelate heavy metal ions by the formation of complexes which, are transported to the vacuoles, where the toxicity is not threatening. For this reason phytochelatins are essential in the detoxification of heavy metal ions in plants. The developed HPLC method uses a mobile phase of 1% of formic acid in water with KNO3 or NaCl (pH=2.00) and 1% of formic acid in acetonitrile. Electrochemical detection at different carbon-based electrodes was used. Among the sensors tested, the conventional glassy carbon electrode offers the best sensitivity although modification improves the sensitivity of the SPCE. Glutathione and several isoforms of phytochelatin two were found in plant extracts of both studied species.

  18. A Facile Electrochemical Preparation of Reduced Graphene Oxide@Polydopamine Composite: A Novel Electrochemical Sensing Platform for Amperometric Detection of Chlorpromazine

    OpenAIRE

    Selvakumar Palanisamy; Balamurugan Thirumalraj; Shen-Ming Chen; Yi-Ting Wang; Vijayalakshmi Velusamy; Sayee Kannan Ramaraj

    2016-01-01

    We report a novel and sensitive amperometric sensor for chlorpromazine (CPZ) based on reduced graphene oxide (RGO) and polydopamine (PDA) composite modified glassy carbon electrode. The RGO@PDA composite was prepared by electrochemical reduction of graphene oxide (GO) with PDA. The RGO@PDA composite modified electrode shows an excellent electro-oxidation behavior to CPZ when compared with other modified electrodes such as GO, RGO and GO@PDA. Amperometric i-t method was used for the determinat...

  19. Amperometric detection of glucose in fruit juices with polypyrrole-based biosensor with an integrated permselective layer for exclusion of interferences.

    Science.gov (United States)

    Ayenimo, Joseph G; Adeloju, Samuel B

    2017-08-15

    A novel polypyrrole (PPy)-based bilayer amperometric glucose biosensor integrated with a permselective layer has been developed for detection of glucose in the presence of interferences. It comprises of a PPy-GOx film grown, in the absence of electrolyte, as an inner layer, and a permselective PPy-Cl film as an outer layer. The PPy-GOx/PPy-Cl bilayer biosensor was effective in rejecting 98% of ascorbic acid and 100% of glycine, glutamic acid and uric acid. With an outer layer thickness of 6.6nm, the bilayer biosensor gave nearly identical glucose response to that of a single layer PPy-GOx biosensor. The biosensor also exhibited good reproducibility (1.9% rsd, n=10), high stability (more than 2months), wide linear range (0.5-24mM), low Km (8.4mM), high Imax (77.2μAcm(-2)), low detection limit (26.9μM) and good sensitivity (3.5μAcm(-2)mM(-1)). The bilayer biosensor was successfully employed for glucose determination in various fruit juices. Copyright © 2017 Elsevier Ltd. All rights reserved.

  20. Short communication: Quantification of carbohydrates in whey permeate products using high-performance anion-exchange chromatography with pulsed amperometric detection.

    Science.gov (United States)

    Lee, Hyeyoung; de MeloSilva, Vitor Luiz; Liu, Yan; Barile, Daniela

    2015-11-01

    A method was developed for the characterization and quantification of the disaccharide lactose and 3 major bovine milk oligosaccharides (BMO) in dairy streams. Based on high-performance anion-exchange chromatography-pulsed amperometric detection (HPAE-PAD), this method is advantageous because it requires minimal sample preparation and achieves good chromatographic separation of oligosaccharide isomers within 30min. The linear dynamic range and limit of detection were 0.1 to 10mg/L and 0.03 to 0.22mg/L, respectively. Mean recoveries of the BMO were excellent and ranged from 98.4 to 100.4%. Without complicated sample preparation procedures, this HPAE-PAD method measured BMO [3'-sialyllactose (3'SL), 6'-sialyllactose (6'SL), and 6'-sialyllactosamine (6'SLN)] and lactose using a single instrument, therefore increasing the accuracy of the measurement and applicability for the dairy industry. In colostrum whey permeate, 3'SL, 6'SL, and 6'SLN were 94, 29, and 46mg/L, respectively. This work is the first to demonstrate that some commercial products, currently marketed for supporting a healthy immune system, contain significant amounts of bioactive BMO and therefore, carry additional bioactivities.

  1. Determination of mutagenic amines in water and food samples by high pressure liquid chromatography with amperometric detection using a multiwall carbon nanotubes-glassy carbon electrode.

    Science.gov (United States)

    Bueno, Ana María; Marín, Miguel Ángel; Contento, Ana María; Ríos, Ángel

    2016-02-01

    A chromatographic method, using amperometric detection, for the sensitive determination of six representative mutagenic amines was developed. A glassy carbon electrode (GCE), modified with multiwall carbon nanotubes (GCE-CNTs), was prepared and its response compared to a conventional glassy carbon electrode. The chromatographic method (HPLC-GCE-CNTs) allowed the separation and the determination of heterocyclic aromatic amines (HAAs) classified as mutagenic amines by the International Agency for Research of Cancer. The new electrode was systematically studied in terms of stability, sensitivity, and reproducibility. Statistical analysis of the obtained data demonstrated that the modified electrode provided better sensitivity than the conventional unmodified ones. Detection limits were in the 3.0 and 7.5 ng/mL range, whereas quantification limits ranged between 9.5 and 25.0 ng/mL were obtained. The applicability of the method was demonstrated by the determination of the amines in several types of samples (water and food samples). Recoveries indicate very good agreement between amounts added and those found for all HAAs (recoveries in the 92% and 105% range).

  2. Flow Injection Analysis of Acid and Base using Thermo-Sensitive Resistance Coils

    OpenAIRE

    1995-01-01

    A flow injection analysis of acid-base by detecting neutralization heat is proposed. A injected sample (acid or base), combined with a carrier (deionized water), was mixed with a reagent (base or acid) stream. A change in the solution temperature was detected by passing the solution, immediately after mixing, through a stainless steel capillary tube around which a thermo-sensitive resistance was coiled. The temperature of carrier was used as a reference Hydrochloric acid solutions of 0.003 to...

  3. Micro-flow-injection analysis (μFIA) immunoassay of herbicide residue 2,6-dichlorobenzamide – towards automated at-line monitoring using modular microfluidics.

    Science.gov (United States)

    Uthuppu, Basil; Heiskanen, Arto; Kofoed, Dan; Aamand, Jens; Jørgensen, Claus; Dufva, Martin; Jakobsen, Mogens Havsteen

    2015-03-07

    As a part of developing new systems for continuously monitoring the presence of pesticides in groundwater, a microfluidic amperometric immunosensor was developed for detecting the herbicide residue 2,6-dichlorobenzamide (BAM) in water. A competitive immunosorbent assay served as the sensing mechanism and amperometry was applied for detection. Both the immunoreaction chip (IRC) and detection (D) unit are integrated on a modular microfluidic platform with in-built micro-flow-injection analysis (μFIA) function. The immunosorbent, immobilized in the channel of the IRC, was found to have high long-term stability and withstand many regeneration cycles, both of which are key requirements for systems utilized in continuous monitoring. The IRC was regenerated during 51 cycles in a heterogeneous competitive assay out of which 27 were without the analyte (the highest possible signal level) in order to assess the regeneration capability of the immunosorbent. Detection of BAM standard solutions was performed in the concentration range from 62.5 μg L(-1) to 0.0008 μg L(-1). Non-linear regression of the data using the four-parameter logistic equation generated a sigmoidal standard curve showing an IC50 value (concentration that reduces the signal by 50%) of 0.25 μg L(-1). The strongest signal variation is observed in the concentration range between 0.02 and 2.5 μg L(-1), which includes the 0.1 μg L(-1) threshold limit set by the European Commission for BAM in drinking water. The presented results demonstrate the potential of the constructed μFIA immunosensor as an at-line monitoring system for controlling the quality of ground water supply.

  4. Microchip CE analysis of amino acids on a titanium dioxide nanoparticles-coated PDMS microfluidic device with in-channel indirect amperometric detection.

    Science.gov (United States)

    Qiu, Jian-Ding; Wang, Li; Liang, Ru-Ping; Wang, Jing-Wu

    2009-10-01

    In this paper, titanium dioxide nanoparticles (TiO(2) NPs) were employed to construct a functional film on PDMS microfluidic channel surface, which was formed by sequentially immobilizing poly(diallyldimethylammonium chloride) and TiO(2) NPs on PDMS surface by layer-by-layer assembly technique. The modified PDMS microchip exhibited a decreased and stable EOF, which was favorable for the separation of biomolecules with similar migration times. Arginine, phenylalanine, serine and threonine were used as model analytes to evaluate the performance of the modified microchip. The four amino acids were efficiently separated within 100 s in a 3.7 cm long separation channel and successfully detected on the carbon fiber electrode in conjunction with in-channel indirect amperometry. Resolutions and theoretical plate numbers of the analytes were considerably enhanced in the presence of TiO(2) NPs. The modified microchip demonstrated excellent stability and reproducibility with improved RSDs of migration times and peak currents for run-to-run, day-to-day and chip-to-chip analyses, respectively. Variables influencing the separation efficiency and amperometric response, including injection and separation voltage, the working electrode position and buffer concentration, were optimized in detail.

  5. Analytical Method for Sugar Profile in Pet Food and Animal Feeds by High-Performance Anion-Exchange Chromatography with Pulsed Amperometric Detection.

    Science.gov (United States)

    Ellingson, David J; Anderson, Phillip; Berg, Daniel P

    2016-01-01

    There is a need for a standardized, accurate, rugged, and consistent method to measure for sugars in pet foods and animal feeds. Many traditional standard sugar methods exist for other matrixes, but when applied in collaborative studies there was poor agreement and sources of error identified with those standard methods. The advancement in technology over the years has given us the ability to improve on these standard methods of analysis. A method is described here that addresses these common issues and was subjected to a single-laboratory validation to assess performance on a wide variety of pet foods and animal feeds. Of key importance to the method performance is the sample preparation before extraction, type of extraction solvent, postextraction cleanup, and, finally, optimized chromatography using high-performance anion exchange chromatography with pulsed amperometric detection. The results obtained from the validation demonstrate how typical issues seen with these matrixes can influence performance of sugar analysis. The results also demonstrate that this method is fit-for-purpose and can meet the challenges of sugar analysis in pet food and animal feeds to lay the foundation for a standardized method of analysis.

  6. Amperometric Choline Biosensor Fabricated through Electrostatic Assembly of Bienzyme/Polyelectrolyte Hybrid Layers on Carbon Nanotubes

    Energy Technology Data Exchange (ETDEWEB)

    Wang, Jun; Liu, Guodong; Lin, Yuehe

    2006-03-01

    We report a flow injection amperometric choline biosensors based on the electrostatic assembly of an enzyme of choline oxidase (ChO) and a bi-enzyme of ChO and horseradish peroxidase (HRP) onto multi-wall carbon nanotubes (MWCNT) modified glassy carbon (GC) electrodes. These choline biosensors were fabricated by immobilization of enzymes on the negatively charged MWCNT surface through alternatively assembling a cationic polydiallydiimethylammonium chloride (PDDA) layer and an enzyme layer. Using this layer-by-layer assembling approach, bioactive nanocomposite film of a PDDA/ChO/PDDA/HRP/PDDA/CNT (ChO/HRP/CNT) and a PDDA/ChO/PDDA/ CNT (ChO/ CNT) were fabricated on GC surface, respectively. Owning to the electrocatalytic effect of carbon nanotubes, the measurement of faradic responses resulting from enzymatic reactions has been realized at low potential with acceptable sensitivity. It is found the ChO/HRP/CNT biosensor is more sensitive than the ChO/CNT one. Experimental parameters affecting the sensitivity of biosensors, e.g. applied potential, flow rate, etc. were optimized and potential interference was examined. The response time for this choline biosensor is fast (less than a few seconds). The linear range of detection for the choline biosensor is from 5 x 10-5 to 5 x 10-3 M and the detection limit is determined to be about 1.0 x 10-5 M.

  7. Electrocatalytic amperometric determination of amitrole using a cobalt-phthalocyanine-modified carbon paste electrode.

    Science.gov (United States)

    Chicharro, Manuel; Zapardiel, Antonio; Bermejo, Esperanza; Moreno, Mónica; Madrid, Elena

    2002-07-01

    Cobalt-phthalocyanine-modified carbon paste electrodes are shown to be excellent indicators for electrocatalytic amperometric measurements of triazolic herbicides such as amitrole, at low oxidation potentials (+0.40 V). The detection and determination of amitrole in flow injection analysis with a modified carbon paste electrode with Co-phthalocyanine is described. The concentrations of amitrole in 0.1 M NaOH solutions were determined using the electrocatalytic oxidation signal corresponding to the Co(II)/Co(III) redox process. A detection limit of 0.04 microg mL(-1) (4 ng amitrole) was obtained for a sample loop of 100 microL at a fixed potential of +0.55 V (vs. Ag/AgCl) in 0.1 M NaOH and a flow rate of 4.0 mL min(-1). Furthermore, the modified carbon paste electrodes offers reproducible responses in such a system, and the relative standard deviation was 3.3% using the same surface, 5.1% using different surface, and 6.9% using different pastes. The performance of the cobalt-phthalocyanine-modified carbon paste electrodes is illustrated here for the determination of amitrole in commercial formulations. The response of the electrodes is stable, with more than 80% of the initial retained activity after 50 min of continuous use.

  8. Flow injection method for sulphide determination using an organic mercury compound

    Energy Technology Data Exchange (ETDEWEB)

    Yaqoob, M.; Anwar, M.; Masood, A.S.; Masoom, M. (Univ. of Balochistan, Quetta (Pakistan))

    1991-04-01

    A simple flow injection analysis method is described for the determination of soluble sulfide, based on the complexation of sulfide with p-hydroxymercurbenzoic acid, in the presence of dithizone used as an indicator. The reaction is very rapid, with a sampling rate of 90/hr. and requires a very short length post injection reaction coil. The detection limit and precision are 0.01 mM and 0.7%, respectively.

  9. A lactose flow injection analysis biosensor system for monitoring and process control

    OpenAIRE

    2004-01-01

    In this work an enzymatic lactose biosensor composed of the immobilized enzymes E- galactosidase and glucose oxidase was developed. Oxygen consumption during the reaction catalyzed by these enzymes was detected. The biosensor was integrated into an FIA (flow injection analysis) system that allows measurement of lactose on-line in less than three minutes. This biosensor was used to monitor lactose concentration during the production of E-galactosidase by the yeast Kluyveromyces marxianus from ...

  10. Direct microcomputer controlled determination of zinc in human serum by flow injection atomic absorption spectrometry

    DEFF Research Database (Denmark)

    Simonsen, Kirsten Wiese; Nielsen, Bent; Jensen, Arne

    1986-01-01

    A procedure is described for the direct determination of zinc in human serum by fully automated, microcomputer controlled flow injection atomic absorption spectrometry (Fl-AAS). The Fl system is pumpless, using the negative pressure created by the nebuliser. It only consists of a three-way valve......, programmable from the microcomputer, to control the sample volume. No pre-treatment of the samples is necessary. The limit of detection is 0.14 mg l–1, and only small amounts of serum (

  11. Current Trends in Nanomaterial-Based Amperometric Biosensors

    Directory of Open Access Journals (Sweden)

    Akhtar Hayat

    2014-12-01

    Full Text Available The last decade has witnessed an intensive research effort in the field of electrochemical sensors, with a particular focus on the design of amperometric biosensors for diverse analytical applications. In this context, nanomaterial integration in the construction of amperometric biosensors may constitute one of the most exciting approaches. The attractive properties of nanomaterials have paved the way for the design of a wide variety of biosensors based on various electrochemical detection methods to enhance the analytical characteristics. However, most of these nanostructured materials are not explored in the design of amperometric biosensors. This review aims to provide insight into the diverse properties of nanomaterials that can be possibly explored in the construction of amperometric biosensors.

  12. Simultaneous separation and quantitative determination of monosaccharides, uronic acids, and aldonic acids by high performance anion-exchange chromatography coupled with pulsed amperometric detection in corn stover prehydrolysates

    Directory of Open Access Journals (Sweden)

    Xing Wang

    2012-11-01

    Full Text Available A method for simultaneous separation and quantitative determination of arabinose, galactose, glucose, xylose, xylonic acid, gluconic acid, galacturonic acid, and glucuronic acid was developed by using high performance anion-exchange chromatography coupled with pulsed amperometric detection (HPAEC-PAD. The separation was performed on a CarboPacTM PA-10 column (250 mm × 2 mm with a various gradient elution of NaOH-NaOAc solution as the mobile phase. The calibration curves showed good linearity (R2 ≥ 0.9993 for the monosaccharides, uronic acids, and aldonic acids in the range of 0.1 to 12.5 mg/L. The detection limits (LODs and the quantification limits (LOQs were 4.91 to 18.75 μg/L and 16.36 to 62.50 μg/L, respectively. Relative standard deviations (RSDs of the retention times and peak areas for the seven consecutive determinations of an unknown amount of mixture were 0.15% to 0.44% and 0.22% to 2.31%, respectively. The established method was used to separate and determine four monosaccharides, two uronic acids, and two aldonic acids in the prehydrolysate from dilute acid steam-exploded corn stover within 21 min. The spiked recoveries of monosaccharides, uronic acids, and aldonic acids ranged from 91.25% to 108.81%, with RSDs (n=3 of 0.04% ~ 6.07%. This method was applied to evaluate the quantitative variation of sugar and sugar acid content in biomass prehydrolysates.

  13. Determination of amino acids in cell culture and fermentation broth media using anion-exchange chromatography with integrated pulsed amperometric detection.

    Science.gov (United States)

    Hanko, Valoran P; Rohrer, Jeffrey S

    2004-01-01

    Cell culture and fermentation broth media are used in the manufacture of biotherapeutics and many other biological materials. Characterizing the amino acid composition in cell culture and fermentation broth media is important because deficiencies in these nutrients can reduce desired yields or alter final product quality. Anion-exchange (AE) chromatography using sodium hydroxide (NaOH) and sodium acetate gradients, coupled with integrated pulsed amperometric detection (IPAD), determines amino acids without sample derivatization. AE-IPAD also detects carbohydrates, glycols, and sugar alcohols. The presence of these compounds, often at high concentrations in cell culture and fermentation broth media, can complicate amino acid determinations. To determine whether these samples can be analyzed without sample preparation, we studied the effects of altering and extending the initial NaOH eluent concentration on the retention of 42 different carbohydrates and related compounds, 30 amino acids and related compounds, and 3 additional compounds. We found that carbohydrate retention is impacted in a manner different from that of amino acid retention by a change in [NaOH]. We used this selectivity difference to design amino acid determinations of diluted cell culture and fermentation broth media, including Bacto yeast extract-peptone-dextrose (yeast culture medium) broth, Luria-Bertani (bacterial culture medium) broth, and minimal essential medium and serum-free protein-free hybridoma medium (mammalian cell culture media). These media were selected as representatives for both prokaryotic and eukaryotic culture systems capable of challenging the analytical technique presented in this paper. Glucose up to 10mM (0.2%, w/w) did not interfere with the chromatography, or decrease recovery greater than 20%, for the common amino acids arginine, lysine, alanine, threonine, glycine, valine, serine, proline, isoleucine, leucine, methionine, histidine, phenylalanine, glutamate, aspartate

  14. Immobilized enzymes in flow-injection analysis: present and trends.

    Science.gov (United States)

    Ruz, J; Lázaro, F; de Castro, M D

    1988-01-01

    An overview of the use of immobilized enzymes in flow-injection analysis (FIA) is presented. The joint use of FIA and immobilized enzymes means that analytical procedures are easily automated, analytical costs are reduced and methods are faster. The future possibilities for this combination are discussed.

  15. Tandem chemiluminescence-flow injection analysis for dimethoate determination.

    OpenAIRE

    Catalá Icardo, Mónica; López Paz, José Luis; CHOVES BARÓN, CRISTINA

    2010-01-01

    Ministry of Education and Science [CTM2006-11991] FEDER funds Catalá Icardo, M.; López Paz, JL.; Choves Barón, C. (2010). Tandem chemiluminescence-flow injection analysis for dimethoate determination. Luminescence. 25:235-236. doi:10.1002/bio.1217. Senia 235 236 25

  16. Implementation of suitable flow injection/sequential-sample separation/preconcentration schemes for determination of trace metal concentrations using detection by electrothermal atomic absorption spectrometry and inductively coupled plasma mass spectrometry

    DEFF Research Database (Denmark)

    Hansen, Elo Harald; Wang, Jianhua

    2002-01-01

    Various preconditioning procedures encomprising appropriate separation/preconcentration schemes in order to obtain optimal sensitivity and selectivity characteristics when using electrothermal atomic absorption spectrometry (ETAAS) and inductively coupled plasma mass spectrometry (ICPMS) are pres......Various preconditioning procedures encomprising appropriate separation/preconcentration schemes in order to obtain optimal sensitivity and selectivity characteristics when using electrothermal atomic absorption spectrometry (ETAAS) and inductively coupled plasma mass spectrometry (ICPMS...... prior to detection are effected in a microconduit placed on top of an SI selection valve....

  17. Direct analysis of carbohydrates in animal plasma by ion chromatography coupled with mass spectrometry and pulsed amperometric detection for use as a non-invasive diagnostic tool.

    Science.gov (United States)

    Kotnik, Darja; Smidovnik, Andrej; Jazbec-Križman, Petra; Križman, Mitja; Prošek, Mirko

    2011-12-01

    The present paper demonstrates that electrochemical detection (ECD) coupled to ion chromatography and electrospray ionization tandem mass spectrometry (IC-ECD-ESI/MS/MS) can be used to rapidly estimate some indications of the health status of organisms. The lactulose to mannitol ratio (L/M) is used as a non-invasive assay to investigate small intestinal absorption pathways and mucosal integrity. In the present study, an evaluation of the negative effects of nonsteroidal anti-inflammatory drug meloxicam perorally administrated to a group of dogs was carried out by determining the lactulose/mannitol index using the IC-ECD-ESI/MS/MS hyphenated technique. According to the results of the study, meloxicam altered gastrointestinal permeability. Coenzyme Q(10) (CoQ(10)) was tested to determine if it could prevent meloxicam induced gastrointestinal damage and it was found that CoQ(10) could be an effective preventive treatment. Furthermore, plasma glucose concentration level was determined to be an indirect indicator of the oxidative state in the blood. To find out the beneficial effects of a double antioxidant combination (α-lipoic acid (ALA) and CoQ(10)) on the total glucose level in chickens, ALA and CoQ(10) were provided as food additives in factory farm raised chicken. The results of the pilot study indicate that the glucose level in the plasma of chickens group fed with CoQ(10) and ALA was significantly decreased compared to the control group. Ion chromatography (IC) utilizing pulsed amperometric detection (PAD) was compared to ion chromatography coupled with tandem mass spectrometry (MS/MS) as an analytical tool for monitoring the carbohydrate level in biological fluids. In electrochemical detection, the newly developed two-pulse waveform successfully withstands matrix effects in biological samples. Continuous on-line desalting of the high salt concentrations used as the eluent for carbohydrate separation from the anion-exchange column allows coupling of IC and MS

  18. DETERMINATION OF HYDROGEN PEROXIDE BY CAPILLARY ELECTROPHORESIS WITH AMPEROMETRIC DETECTION%毛细管电泳电化学法检测过氧化氢

    Institute of Scientific and Technical Information of China (English)

    董冉冉; 张燕; 时克林; 马艳芳; 李玲君; 王晓蕾

    2011-01-01

    以金微盘电极和离子液体修饰单壁碳纳米管糊微盘电极分别作为毛细管电泳电化学检测器,试验了两种电极对过氧化氢的响应情况,将金微盘电极与毛细管电泳联用,对过氧化氢进行了定性和定量检测.探讨了分离电压、缓冲溶液pH值和工作电位等条件对H2O2检测的影响.实验结果表明,峰电流与H2O2浓度在1.0×10-6~1.0×10-5mol/L和3.0×104~1.0×10-3 mol/L呈良好的线性,线性回归方程分别为y(nA)=0.041 78+0.015 5x(μmol/L),y(A)=-3.3045×10-4+0.024 29x (mmol/L),相关系数分别为0.9975和0.9990,当信噪比S/N=3时,浓度检出限为5×l0-7mol/L.实验中发现,样品中的多巴胺、抗坏血酸等对H2O2的测定无干扰.%Gold microelectrode and ionic liquid modified-SWNTs paste microelectrode made by ourselves were used in capillary zone electrophoresis with electrochemical end-column amperometric detection to determine hydrogen peroxide. Gold microelectrode showed higher sensitivity to H2O2 was used as the detector of capillary electrophoresis. Factors influencing the performance, including separation voltage, detection potential and pH value of the buffer were studied. Under optimized detection conditions, hydrogen peroxide responded linearly from 1.0 x 10-5-1 x 10-3 mol/L and 3.0 x 10~5-10 x 10-3 with a correlation coefficient of 0.9975 and 0.999 0 respectively. The concentration limit of detection of the method was 5 x 10~7 mol/L (S/N=3 ). The experiment also showed that there was no electroactive interferences such as dopamine and ascorbic acid.

  19. Flow Injection and Atomic Absorption Spectrometry - An Effective and Attractive Analytical Chemical Combination

    DEFF Research Database (Denmark)

    Hansen, Elo Harald; Nielsen, Steffen

    1998-01-01

    One of the advantages of the flow injection (FI) concept is that it is compatible with virtually all detection techniques. Being a versatile vehicle for enhancing the performance of the individual detection devices, the most spectacular results have possibly been obtained in conjunction with atomic...... is subjected to in FI from the point of injection/introduction to the point of detection, which in turn allows suitable on-line pretreatments to be effected. The present paper will - via a number of selected examples - point to some of the potentials at hand, encompassing the use of FI as a suitable vehicle...

  20. Potentiometric electronic tongue-flow injection analysis system for the monitoring of heavy metal biosorption processes.

    Science.gov (United States)

    Wilson, D; del Valle, M; Alegret, S; Valderrama, C; Florido, A

    2012-05-15

    An automated flow injection potentiometric (FIP) system with electronic tongue detection (ET) is used for the monitoring of biosorption processes of heavy metals on vegetable wastes. Grape stalk wastes are used as biosorbent to remove Cu(2+) ions in a fixed-bed column configuration. The ET is formed by a 5-sensor array with Cu(2+) and Ca(2+)-selective electrodes and electrodes with generic response to heavy-metals, plus an artificial neural network response model of the sensor's cross-response. The real-time monitoring of both the Cu(2+) and the cation exchanged and released (Ca(2+)) in the effluent solution is performed by using flow-injection potentiometric electronic tongue system. The coupling of the electronic tongue with automation features of the flow-injection system allows us to accurately characterize the Cu(2+) ion-biosorption process, through obtaining its breakthrough curves, and the profile of the Ca(2+) ion release. In parallel, fractions of the extract solution are analysed by spectroscopic techniques in order to validate the results obtained with the reported methodology. The sorption performance of grape stalks is also evaluated by means of well-established sorption models.

  1. A label-free amperometric immunosensor for detection of zearalenone based on trimetallic Au-core/AgPt-shell nanorattles and mesoporous carbon

    Energy Technology Data Exchange (ETDEWEB)

    Liu, Lei; Chao, Yingjun; Cao, Wei, E-mail: chm_caow@ujn.edu.cn; Wang, Yulan; Luo, Chuannan; Pang, Xuehui; Fan, Dawei; Wei, Qin, E-mail: sdjndxwq@163.com

    2014-10-17

    Highlights: • Au@AgPt nanorattles have special structure of Au-core and imperfect AgPt-shell. • Au@AgPt are proposed for the first time applied in electrochemical immunosensor. • Substrate materials MC/Au@AgPt possess excellent conductivity and high surface area. • The proposed immunosensor exhibits a low detection limit of 1.7 pg mL{sup −1}. - Abstract: A novel label-free amperometric immunosensor is proposed for the ultrasensitive detection of zearalenone (ZEN) based on mesoporous carbon (MC) and trimetallic nanorattles (core/shell particles with movable cores encapsulated in the shells). The nanorattles are composed of special Au-core and imperfect AgPt-shell structure (Au@AgPt). The Au@AgPt nanorattles are loaded onto the MC by physical adsorption. The structure of the Au@AgPt nanorattles was characterized by using scanning electron microscopy (SEM) and transmission electron microscopy (TEM). Energy dispersive X-ray spectroscopy (EDS) confirmed the composition of the synthesized nanorattles. Compared with monometallic and bimetallic nanoparticles (NPs), Au@AgPt nanorattles show a higher electron transfer rate due to the synergistic effect of the Au, Ag and Pt NPs. MC further improves the sensitivity of the immunosensor because of its extraordinarily large specific surface area, suitable pore arrangement and outstanding conductivity. The large specific surface area of MC and MC@Au@AgPt were characterized by the BET method. ZEN antibodies are immobilized onto the nanorattles via Ag–NH{sub 2} bonds and Pt–NH{sub 2} bonds. Cyclic voltammetry and square wave voltammetry were used to characterize the recognizability of ZEN. Under optimum experimental conditions, the proposed immunosensor exhibited a low detection limit (1.7 pg mL{sup −1}), a wide linear range (from 0.005 to 15 ng mL{sup −1}) as well as good stability, reproducibility and selectivity. The sensor can be used in clinical analysis.

  2. Fe3O4 nanoparticles on graphene oxide sheets for isolation and ultrasensitive amperometric detection of cancer biomarker proteins.

    Science.gov (United States)

    Sharafeldin, Mohamed; Bishop, Gregory W; Bhakta, Snehasis; El-Sawy, Abdelhamid; Suib, Steven L; Rusling, James F

    2017-05-15

    Ultrasensitive mediator-free electrochemical detection for biomarker proteins was achieved at low cost using a novel composite of Fe3O4 nanoparticles loaded onto graphene oxide (GO) nano-sheets (Fe3O4@GO). This paramagnetic Fe3O4@GO composite (1µm size range) was decorated with antibodies against prostate specific antigen (PSA) and prostate specific membrane antigen (PSMA), and then used to first capture these biomarkers and then deliver them to an 8-sensor detection chamber of a microfluidic immunoarray. Screen-printed carbon sensors coated with electrochemically reduced graphene oxide (ERGO) and a second set of antibodies selectively capture the biomarker-laden Fe3O4@GO particles, which subsequently catalyze hydrogen peroxide reduction to detect PSA and PSMA. Accuracy was confirmed by good correlation between patient serum assays and enzyme-linked immuno-sorbent assays (ELISA). Excellent detection limits (LOD) of 15 fg/mL for PSA and 4.8 fg/mL for PSMA were achieved in serum. The LOD for PSA was 1000-fold better than the only previous report of PSA detection using Fe3O4. Dynamic ranges were easily tunable for concentration ranges encountered in serum samples by adjusting the Fe3O4@GO Concentration. Reagent cost was only $0.85 for a single 2-protein assay.

  3. In-channel indirect amperometric detection of nonelectroactive anions for electrophoresis on a poly(dimethylsiloxane) microchip.

    Science.gov (United States)

    Xu, Jing-Juan; Peng, Ying; Bao, Ning; Xia, Xing-Hua; Chen, Hong-Yuan

    2005-10-01

    In the present paper, we describe a microfluidics-based sensing system for nonelectroactive anions under negative separation electric field by mounting a single carbon fiber disk working electrode (WE) in the end part of a poly(dimethylsiloxane) microchannel. In contrast to work in a positive separation electric field described in our previous paper (Anal. Chem. 2004, 76, 6902-6907), here the electrochemical reduction reaction at the WE is not coupled with the separation high-voltage (HV) system, whereas the electrochemical oxidation reaction at the WE is coupled with the separation HV system. The electroactive indicator is the carbon fiber WE itself but not dissolved oxygen. This provides a convenient and sensitive means for the determination of nonelectroactive anions by amperometry. The influences of separation voltage, detection potential, and the distance between the WE and the separation channel outlet on the response of the detector have been investigated. The present detection mode is successfully used to electrochemically detect F-, Cl-, SO4(2-), CH3COO-, H2PO4-. Based on the preliminary results, a detection limit of 2 microM and a dynamic range up to three orders of magnitude for Cl- could be achieved.

  4. On-line solid-phase enrichment coupled to packed reactor flow injection analysis in a green analytical procedure to determine low levels of folic acid using fluorescence detection

    Directory of Open Access Journals (Sweden)

    Emara Samy

    2012-12-01

    Full Text Available Abstract Background Analysis of folic acid (FA is not an easy task because of its presence in lower concentrations, its lower stability under acidic conditions, and its sensitiveness against light and high temperature. The present study is concerned with the development and validation of an automated environmentally friendly pre-column derivatization combined by solid-phase enrichment (SPEn to determine low levels of FA. Results Cerium (IV trihydroxyhydroperoxide (CTH as a packed oxidant reactor has been used for oxidative cleavage of FA into highly fluorescent product, 2-amino-4-hydroxypteridine-6-carboxylic acid. FA was injected into a carrier stream of 0.04 M phosphate buffer, pH 3.4 at a flow-rate of 0.25 mL/min. The sample zone containing the analyte was passed through the CTH reactor thermostated at 40°C, and the fluorescent product was trapped and enriched on a head of small ODS column (10 mm x 4.6 mm i.d., 5 μm particle size. The enriched product was then back-flush eluted by column-switching from the small ODS column to the detector with a greener mobile phase consisting of ethanol and phosphate buffer (0.04M, pH 3.4 in the ratio of 5:95 (v/v. The eluent was monitored fluorimetrically at emission and excitation wavelengths of 463 and 367 nm, respectively. The calibration graph was linear over concentrations of FA in the range of 1.25-50 ng/mL, with a detection limit of 0.49 ng/mL. Conclusion A new simple and sensitive green analytical procedure including on-line pre-column derivatization combined by SPEn has been developed for the routine quality control and dosage form assay of FA at very low concentration level. The method was a powerful analytical technique that had excellent sensitivity, sufficient accuracy and required relatively simple and inexpensive instrumentation.

  5. Flow-Injection Responses of Diffusion Processes and Chemical Reactions

    DEFF Research Database (Denmark)

    Andersen, Jens Enevold Thaulov

    2000-01-01

    The technique of Flow-injection Analysis (FIA), now aged 25 years, offers unique analytical methods that are fast, reliable and consuming an absolute minimum of chemicals. These advantages together with its inherent feasibility for automation warrant the future applications of FIA as an attractive...... be used in the resolution of FIA profiles to obtain information about the content of interference’s, in the study of chemical reaction kinetics and to measure absolute concentrations within the FIA-detector cell....

  6. Amperometric Biosensor Based on Zirconium Oxide/Polyethylene Glycol/Tyrosinase Composite Film for the Detection of Phenolic Compounds.

    Science.gov (United States)

    Ahmad, Nor Monica; Abdullah, Jaafar; Yusof, Nor Azah; Ab Rashid, Ahmad Hazri; Abd Rahman, Samsulida; Hasan, Md Rakibul

    2016-06-29

    A phenolic biosensor based on a zirconium oxide/polyethylene glycol/tyrosinase composite film for the detection of phenolic compounds has been explored. The formation of the composite film was expected via electrostatic interaction between hexacetyltrimethylammonium bromide (CTAB), polyethylene glycol (PEG), and zirconium oxide nanoparticles casted on screen printed carbon electrode (SPCE). Herein, the electrode was treated by casting hexacetyltrimethylammonium bromide on SPCE to promote a positively charged surface. Later, zirconium oxide was mixed with polyethylene glycol and the mixture was dropped cast onto the positively charged SPCE/CTAB. Tyrosinase was further immobilized onto the modified SPCE. Characterization of the prepared nanocomposite film and the modified SPCE surface was investigated by scanning electron microscopy (SEM), Electrochemical Impedance Spectroscopy (EIS), and Cyclic voltamogram (CV). The developed biosensor exhibits rapid response for less than 10 s. Two linear calibration curves towards phenol in the concentrations ranges of 0.075-10 µM and 10-55 µM with the detection limit of 0.034 µM were obtained. The biosensor shows high sensitivity and good storage stability for at least 30 days.

  7. Amperometric detection of Sudan I in red chili powder samples using Ag nanoparticles decorated graphene oxide modified glassy carbon electrode.

    Science.gov (United States)

    Prabakaran, E; Pandian, K

    2015-01-01

    A simple and sensitive electrochemical method was developed to determine the concentration of Sudan I in chili powder based on silver nanoparticles decorated graphene oxide modified glassy carbon electrode (AgNPs@GO/GCE). The voltammetry behaviour of Sudan I on modified GCE was investigated in phosphate buffer medium (PBS) with various pH ranges and the electron transfer properties were studied. It is found that the AgNPs@GO/GCE can catalyse the reduction of azo group, -N=N- followed by electrochemical oxidation of (-)OH group present in Sudan I dye molecule. Quantitative detection of Sudan I present in food products was carried out by amperometry method in which reduction potential was fixed at -0.77 V vs. Ag/AgCl. The amperometry method showed an excellent performance with a sensitivity of 6.83 μA mM(-1) and a detection limit of 11.4 × 10(-7)ML(-1). A linear calibration graph was constructed in the ranging 3.90 × 10(-6) to 3.19 × 10(-5)ML(-1). The method was successfully applied for the determination of Sudan I in red chili powder samples.

  8. Fabrication of a gold microelectrode for amperometric detection on a polycarbonate electrophoresis chip by photodirected electroless plating.

    Science.gov (United States)

    Kong, Yong; Chen, Hengwu; Wang, Yurong; Soper, Steven A

    2006-07-01

    A novel method of photoresist-free micropatterning coupled with electroless gold plating is described for the fabrication of an integrated gold electrode for electrochemical detection (ED) on a polycarbonate (PC) electrophoresis microchip. The microelectrode layout was photochemically patterned onto the surface of a PC plate by selective exposure of the surface coated without photoresist to 254 nm UV light through a chromium/quartz photomask. Thus, the PC plate was selectively sensitized by formation of reactive chemical moieties in the exposed areas. After a series of wet chemistry reactions, the UV-exposed area was activated with a layer of gold nanoparticles that served as a seed to catalyze the electroless plating. The gold microelectrode was then selectively plated onto the activated area by using an electroless gold plating bath. Nonselective gold deposition on the unwanted areas was eliminated by sonication of the activated PC plate in a KSCN solution before electroless plating, and the adhesion of the plated electrodes to the PC surface was strengthened with thermal annealing. Compared with the previously reported electroless plating technique for fabrication of microelectrodes on a microchip, the present method avoided the use of a membrane stencil with an electrode pattern to restrict the area to be wet-chemically sensitized. The CE with integrated ED (CE-ED) microchip was assembled by thermal bonding an electrode-plated PC cover plate to a microchannel-embossed PC substrate. The novel method allows one to fabricate low-cost, electrode-integrated, complete PC CE-ED chips with no need of a clean room. The fabricated CE-ED microchip was demonstrated for separation and detection of model analytes, including dopamine (DA) and catechol (CA). Detection limits of 0.65 and 1.03 microM were achieved for DA and CA, respectively, and theoretical plate number of 1.4 x 10(4) was obtained for DA. The plated gold electrode can be used for about 4 h, bearing usually more

  9. Determination of parabens in shampoo using high performance liquid chromatography with amperometric detection on a boron-doped diamond electrode.

    Science.gov (United States)

    Martins, Isarita; Carreira, Franciely Cristiani; Canaes, Larissa S; de Souza Campos Junior, Francisco Alberto; da Silva Cruz, Letícia Maria; Rath, Susanne

    2011-07-15

    Methylparaben (MePa), ethylparaben (EtPa) and propylparaben (PrPa) have been widely used, among others, as chemical preservatives in cosmetics, drugs and foods. As these compounds are linked with allergies, dermatitis and estrogenic properties, it is necessary to control the concentration of these substances in different matrices. The aim of this paper are: to evaluate the electrochemical behavior of parabens on the boron-doped diamond (BDD) electrode and the development of a chromatographic method, with electrochemical detection (HPLC-ED), for determination of parabens in shampoo. A BDD (8000 ppm) electrode was adapted in a thin layer mode analytical cell consisting of a stainless steel and a platinum wire as reference and auxiliary electrodes, respectively. Chromatographic separations were obtained with a reversed phase C8 analytical column and a mobile phase of 0.025 molL(-1) disodium phosphate, pH 7.0, and acetonitrile (40:60, v/v), delivered at a flow rate of 1.0 mL min(-1). Sample preparation was performed by solid phase extraction using C18 cartridges and acetonitrile for elution. Benzylparaben was employed as internal standard. The HPLC-ED method developed, using the BDD electrode, was validated for the determination of parabens in shampoos and presented adequate linearity (>0.999), in the range of 0.0125-0.500% (w/w), detectability 0.01% (w/w), precision (RSD of 2.3-9.8%) and accuracy (93.1-104.4%) and could be applied for routine quality control of shampoos containing MePa, EtPa and PrPa. Copyright © 2011 Elsevier B.V. All rights reserved.

  10. A multidimensional high performance liquid chromatography method coupled with amperometric detection using a boron-doped diamond electrode for the simultaneous determination of sulfamethoxazole and trimethoprim in bovine milk

    Energy Technology Data Exchange (ETDEWEB)

    Andrade, Leonardo S.; Moraes, Marcela C. de; Rocha-Filho, Romeu C.; Fatibello-Filho, Orlando [Departamento de Quimica, Universidade Federal de Sao Carlos, C.P. 676, 13560-970 Sao Carlos - SP (Brazil); Cass, Quezia B., E-mail: quezia@pesquisador.cnpq.br [Departamento de Quimica, Universidade Federal de Sao Carlos, C.P. 676, 13560-970 Sao Carlos - SP (Brazil)

    2009-11-10

    The development and validation of a multidimensional HPLC method using an on-line clean-up column coupled with amperometric detection employing a boron-doped diamond (BDD) electrode for the simultaneous determination of sulfamethoxazole (SMX) and trimethoprim (TMP) in bovine milk are presented. Aliquots of pre-prepared skim-milk samples were directly injected into a RAM octyl-BSA column in order to remove proteins that otherwise would interfere with milk analysis. After exclusion of the milk proteins, SMX and TMP were transferred to the analytical column (an octyl column) and the separation of the compounds from one another and from other endogenous milk components was achieved. SMX and TMP were detected amperometrically at 1.25 V vs. Ag/AgCl (3.0 mol L{sup -1} KCl). Results with good linearity in the concentration ranges 50-800 and 25-400 {mu}g L{sup -1} for SMX and TMP, respectively, were obtained and no fouling of the BDD electrode was observed within the experimental period of several hours. The intra- and inter-assay coefficients of variation were less than 10% for both drugs and the obtained LOD values for SMX and TMP were 25.0 and 15.0 {mu}g L{sup -1}, respectively.

  11. Potentiometric electronic tongue-flow injection analysis system for the monitoring of heavy metal biosorption processes

    OpenAIRE

    2012-01-01

    An automated flow injection potentiometric (FIP) system with electronic tongue detection (ET) is used for the monitoring of biosorption processes of heavy metals on vegetable wastes. Grape stalk wastes are used as biosorbent to remove Cu2+ ions in a fixed-bed column configuration. The ET is formed by a 5-sensor array with Cu2+ and Ca2+-selective electrodes and electrodes with generic response to heavy-metals, plus an artificial neural network response model of the sensor's cross-response. The...

  12. Sequential injection lab-on-valve: the third generation of flow injection analysis

    DEFF Research Database (Denmark)

    Wang, Jianhua; Hansen, Elo Harald

    2003-01-01

    Termed the third generation of flow injection analysis, sequential injection (SI)-lab-on-valve (LOV) has specific advantages and allows novel, unique applications - not least as a versatile front end to a variety of detection techniques. This review presents snd discusses progress to date of the SI......-LOV approach as well as its applications in the automation and micro-miniaturization of on-line sample pre-treatment. Special emphasis is placed on using SI-LOV in conjunction with bead injection (BI) for on-line separation and pre-concentration of ultra-trace levels of metals by exploiting the renewable micro...

  13. Flow Injection Analysis of Histidine with Enhanced Electrogenerated Chemiluminescence of Luminol

    Institute of Scientific and Technical Information of China (English)

    2002-01-01

    A simple and sensitive flow injection method is presented for the determination of histidine based on its enhancement of electrogenerated chemiluminescence (ECL) of luminol. After optimization of the experimental parameters, the working range for histidine was in 1.0 x 10-6 to 1.0 x 10 -3 mol/L with a detection limit (S/N = 3) of 0.56 μmol/L. The relative standard deviation was 1.6% for 11 measurements of 5 x 10 -5 mol/L histidine solution. The proposed method has been successfully applied to the determination of histidine in real pharmaceutical preparation.

  14. Chemiluminescence Determination of Molybdenum by on-Line Reduction with a Flow Injection System

    Institute of Scientific and Technical Information of China (English)

    2000-01-01

    The chemiluminescence (CL) reaction between lucigenin (Lu) and molybdenum (Ⅲ) produced by a Jones reductor was investigated using a flow injection system. On the basis of this, a novel method for the determination of trace amount of molybdenum has been established. The emission intensity was linear with molybdenum concentration in the range of 0.1-1000 ng/mL; the detection limit was 0.02 ng/mL molybdenum; the relative standard deviation was less than 2% for the determination of 0.1 ng/mL molybdenum (n=11). The method has been applied successfully to the analysis of trace molybdenum in water and steel samples.

  15. A new amperometric glucose biosensor based on screen printed carbon electrodes with rhenium(IV - oxide as a mediator

    Directory of Open Access Journals (Sweden)

    ALBANA VESELI

    2012-11-01

    Full Text Available Rhenium(IV-oxide, ReO2, was used as a mediator for carbon paste (CPE and screen printed carbon (SPCE electrodes for the catalytic amperometric determination of hydro-gen peroxide, whose overpotential for the reduction could be lowered to -0.1 V vs. Ag/AgCl in flow injection analysis (FIA using phosphate buffer (0.1 M, pH=7.5 as a carrier. For hydrogen peroxide a detection limit (3σ of 0.8 mg L-1 could be obtained.ReO2-modified SPCEs were used to design biosensors with a template enzyme, i.e. glucose oxidase, entrapped in a Nafion membrane. The resulting glucose sensor showed a linear dynamic range up to 200 mg L-1 glucose with a detection limit (3σ of 0.6 mg L-1. The repeatability was 2.1 % RSD (n = 5 measurements, the reproducibility 5.4 % (n = 5 sensors. The sensor could be applied for the determination of glucose in blood serum in good agreement with a reference method.

  16. Flow-injection Chemiluminescence Determination of Trace Calf Thymus DNA

    Institute of Scientific and Technical Information of China (English)

    Min ZHOU; Yong Jun MA; Xiao Yong JIN; Xiu Lan TENG; Zi Yu ZHANG; Hui CHEN

    2003-01-01

    A flow injection procedure for the determination of calf thymus DNA (CT DNA) overthe range 2.1x10-6~2.1×10-1 μg mL-1 is described, based on measurement of the enhancedchemiluminescence emission of rhodamine B-Ce(Ⅳ) system, activated by imidazole-HCl buffersolution. This method is highly sensitive, with the linearity range broadened to five orders ofmagnitude. It has been applied to determine CT DNA in synthetic sample with satisfactoryresults.

  17. Determination of uranium and zirconium by flow injection analysis

    Energy Technology Data Exchange (ETDEWEB)

    Sousa, Alvaro S.F. de; Domingues, Maria de L.F.; Rocha, Valeska P. de Araujo; Jesus, Camila S. de, E-mail: alvaro@ien.gov.br, E-mail: valeska@ien.gov.br, E-mail: luma@ien.gov.br, E-mail: camilasaj@gmail.com [Instituto de Engenharia Nuclear (IEN/CNEN-RJ), Rio de Janeiro, RJ (Brazil)

    2013-07-01

    As an integral part of chemical quality control of nuclear materials a method for determination of uranium and zirconium, in a mixture is presented. A simple, cheap, selective and quantitative Flow Injection Analysis (FIA) system was developed. Zirconium and uranium were determinate in presence of each other and no prior separation was needed. Arsenazo III was used as a colorimetric reagent and parameters such as acidity and reagents concentration were studied and optimized. An analytical throughput of 30 sample determination per hour was obtained. (author)

  18. Flow injection analysis of picric acid explosive using a copper electrode as electrochemical detector.

    Science.gov (United States)

    Junqueira, João R C; de Araujo, William R; Salles, Maiara O; Paixão, Thiago R L C

    2013-01-30

    A simple and fast electrochemical method for quantitative analysis of picric acid explosive (nitro-explosive) based on its electrochemical reduction at copper surfaces is reported. To achieve a higher sample throughput, the electrochemical sensor was adapted in a flow injection system. Under optimal experimental conditions, the peak current response increases linearly with picric acid concentration over the range of 20-300 μmol L(-1). The repeatability of the electrode response in the flow injection analysis (FIA) configuration was evaluated as 3% (n=10), and the detection limit of the method was estimated to be 6.0 μmol L(-1) (S/N=3). The sample throughput under optimised conditions was estimated to be 550 samples h(-1). Peroxide explosives like triacetone triperoxide (TATP) and hexamethylene triperoxide diamine (HMTD) were tested as potential interfering substances for the proposed method, and no significant interference by these explosives was noticed. The proposed method has interesting analytical parameters, environmental applications, and low cost compared with other electroanalytical methods that have been reported for the quantification of picric acid. Additionally, the possibility to develop an in situ device for the detection of picric acid using a disposable sensor was evaluated.

  19. Application of flow-injection potentiometric system for determination of total concentration of aliphatic carboxylic acids.

    Science.gov (United States)

    Mroczkiewicz, Monika; Górski, Łukasz; Zamojska-Jaroszewicz, Anna; Szewczyk, Krzysztof W; Malinowska, Elżbieta

    2011-09-30

    In this work, flow-injection system with potentiometric detection was tested for determination of total carboxylic acid concentration. Detection part of the examined system consists of ion-selective electrodes (ISEs) with polymer membranes of different compositions. First electrode is based on Zr(IV)-tetraphenylporphyrin as ionophore selective towards carboxylic acid anions, the membrane of second one contains only liphophilic anion exchanger - tridodecylmethylammonium chloride. Final response of the system is a result of combination of EMF signals from both electrodes. Combination of two detectors enables significant decrease of differences between potentiometric signals induced by mixtures of studied anions of various concentrations as compared to results obtained only with metalloporphyrin-based ISE. The use of anion-exchanger based detector allows for elimination of the influence of aliphatic carboxylic acids lipophilicity. Proposed potentiometric flow-injection system was employed for determination of short-chain aliphatic carboxylic acids (so-called VFA - volatile fatty acids) in samples originating from an anaerobic digester. Results obtained for these relatively complicated samples are in good agreement with results obtained with the use of reference colorimetric method. Linear response towards carboxylic acids was observed in the concentration range of 10(-4) to 10(-2)mold m(-3), with the slopes in the range of -110 to -150 mV dec(-1) (for acetate(-) and butyrate(-), respectively). System enables for determination of about 6 samples per hour. Life time of ISEs average about 2 months.

  20. Application of high-performance anion-exchange chromatography with pulsed amperometric detection and statistical analysis to study oligosaccharide distributions--a complementary method to investigate the structure and some properties of alginates.

    Science.gov (United States)

    Ballance, Simon; Holtan, Synnøve; Aarstad, Olav Andreas; Sikorski, Pawel; Skjåk-Braek, Gudmund; Christensen, Bjørn E

    2005-11-04

    Alginates comprised of essentially alternating units of mannuronic (M) acid-guluronic (G) acid (MG-alginate), and G-blocks isolated from a seaweed where subjected to partial acid hydrolysis at pH 3.5 The chain-length distribution of oligosaccharides in the hydrolysate were investigated by statistical analysis after their separation with high-performance anion-exchange chromatography and pulsed amperometric detection (HPAEC-PAD). Simulated depolymerisation of the MG-alginate provided an estimate of the ratio between two acid hydrolysis rate constants (p=8.3+/-1) and the average distribution of the MM linkages in the original sample of polysaccharide chains. In conclusion, we found HPAEC-PAD together with statistical analysis was a useful method to investigate the fine structure and some properties of binary polysaccharides.

  1. Selective determination of chlorine dioxide using gas diffusion flow injection analysis

    Energy Technology Data Exchange (ETDEWEB)

    Hollowell, D.A.; Pacey, G.E.; Gordon, G.

    1985-12-01

    An automated absorbance technique for the determination of aqueous chlorine dioxide has been developed by utilizing gas diffusion flow injection analysis. A gas diffusion membrane is used to separate the donor (sampling) stream from the acceptor (detecting) stream. The absorbance of chlorine dioxide is monitored at 359 nm. The first method uses distilled water as the acceptor stream and gives a detection limit of 0.25 mg/L chlorine dioxide. This system is over 550 times more selective for chlorine dioxide than chlorine. To further minimize chlorine interference, oxalic acid is used in the acceptor stream. The detection limit for this system is 0.45 mg/L chlorine dioxide. This second system is over 5400 times more selective for chlorine dioxide than chlorine. Both methods show excellent selectivity for chlorine dioxide over iron and manganese compounds, as well as other oxychlorinated compounds such as chlorite and perchlorate ions. 18 references, 7 figures, 3 tables.

  2. Flow injection chemiluminescence determination of hydrazine by oxidation with chlorinated isocyanurates.

    Science.gov (United States)

    Safavi, Afsaneh; Karimi, Mohammad Ali

    2002-10-16

    A rapid and sensitive flow injection chemiluminescence (CL) method is described for the determination of hydrazine based on the CL generated during its reaction with either sodium dichloroisocyanurate (SDCC) or trichloroisocyanuric acid (TCCA) in alkaline medium. The emission intensity is greatly enhanced if dichlorofluorescein (DCF) as sensitizer is present in the reaction medium. The presence of citrate prevents the precipitation of some cations in the reaction medium and also causes an enhancement in emission intensity. The effect of analytical and flow injection variables on these CL systems and determination of hydrazine are discussed. The optimum parameters for the determination of hydrazine were studied and were found to be the following: SDCC and TCCA both 1x10(-3) M; NaOH, 2x10(-1) M; DCF, 5x10(-6) M; citrate, 1x10(-3) M and flow rate, 3.8 ml min(-1). The optimized method yielded 3sigma detection limits of 2x10(-7) and 3x10(-7) M for hydrazine with SDCC and TCCA oxidants, respectively. The method is simple, fast, sensitive, and precise and was applied to the determination of hydrazine in water samples.

  3. Tetracycline, oxytetracycline and chlortetracycline determination by flow injection potentiometry.

    Science.gov (United States)

    Couto, C M; Lima, J L; Conceição, M; Montenegro, B S; Reis, S

    1998-12-01

    This paper describes tetracycline (TCH), oxytetracycline (OTCH) and chlortetracycline (CTCH) determination by flow injection potentiometry. In the flow system proposed TC samples are inserted in a carrier solution and converged with a Cu(II) solution of known concentration; the Cu(II) decrease due to its complexation with tetracyclines (TC) was monitored. The detector used was a homogeneous crystalline CuS/Ag2S double membrane tubular electrode with increased sensitivity. The present system allows tetracyclines determinations within a 48.1-4.8 x 10(3) ppm for TCH, 49.1-4.9 x 10(3) ppm for OTCH and 51.5-5.1 x 10(3) ppm for CTCH and a precision better than 0.4% for the three TC species. This procedure accomplishes 150-200 samples h(-1) with a Cu(II) consumption of about 13 microg determination(-1).

  4. Chemiluminometric hydrogen peroxide sensor for flow injection analysis

    Energy Technology Data Exchange (ETDEWEB)

    Preuschoff, F. (Inst. fuer Biotechnologie, Halle Univ. (Germany)); Spohn, U. (Inst. fuer Biotechnologie, Halle Univ. (Germany)); Blankenstein, G. (Inst. fuer Enzymtechnologie am Forschungszentrum Juelich GmbH, Duesseldorf Univ., Juelich (Germany)); Mohr, K.H. (Inst. fuer Biotechnologie, Halle Univ. (Germany)); Kula, M.R. (Inst. fuer Enzymtechnologie am Forschungszentrum Juelich GmbH, Duesseldorf Univ., Juelich (Germany))

    1993-08-01

    A chemiluminometric hydrogen peroxide sensor was developed for fast flow injection analysis. Different peroxidases were covalently immobilized on affinity membranes and compared with respect to the catalytic luminol oxidation. A photomultiplier tube is connected with a fibre bundle to the flow cell. The small cell volume of 5-10 [mu]l allows sampling rates between 90 and 200/h, depending on the flow rate. The highest sensitivity and the best longterm stability can be achieved with microbial peroxidase. Hydrogen peroxide can be determined in the range between 10[sup -3] and 10[sup -8] mol/l with a precision of < 3% (n=6, [alpha] = 0.05). The operational stability of the sensor is longer than 10 weeks. (orig.)

  5. Study of the voltammetric behaviour of metam and its application to an amperometric flow system.

    Science.gov (United States)

    Barroso, M Fátima; Paíga, Paula; Vaz, M Carmo V F; Delerue-Matos, Cristina

    2005-11-01

    The electrochemical behaviour of the pesticide metam (MT) at a glassy carbon working electrode (GCE) and at a hanging mercury drop electrode (HMDE) was investigated. Different voltammetric techniques, including cyclic voltammetry (CV) and square wave voltammetry (SWV), were used. An anodic peak (independent of pH) at +1.46 V vs AgCl/Ag was observed in MT aqueous solution using the GCE. SWV calibration curves were plotted under optimized conditions (pH 2.5 and frequency 50 Hz), which showed a linear response for 17-29 mg L(-1). Electrochemical reduction was also explored, using the HMDE. A well defined cathodic peak was recorded at -0.72 V vs AgCl/Ag, dependent on pH. After optimizing the operating conditions (pH 10.1, frequency 150 Hz, potential deposition -0.20 V for 10 s), calibration curves was measured in the concentration range 2.5 x 10(-1) to 1.0 mg L(-1) using SWV. The electrochemical behaviour of this compound facilitated the development of a flow injection analysis (FIA) system with amperometric detection for the quantification of MT in commercial formulations and spiked water samples. An assessment of the optimal FIA conditions indicated that the best analytical results were obtained at a potential of +1.30 V, an injection volume of 207 muL and an overall flow rate of 2.4 ml min(-1). Real samples were analysed via calibration curves over the concentration range 1.3 x 10(-2) to 1.3 mg L(-1). Recoveries from the real samples (spiked waters and commercial formulations) were between 97.4 and 105.5%. The precision of the proposed method was evaluated by assessing the relative standard deviation (RSD %) of ten consecutive determinations of one sample (1.0 mg L(-1)), and the value obtained was 1.5%.

  6. The Determination of Iodide Based on a Flow-injection Coupling Irreversible Biamperometry

    Institute of Scientific and Technical Information of China (English)

    Li Jun LI; Hao CHENG; Wen Yi HUANG; Hong Xing KONG; Jian Ling WU; Jian Ping LU; Wei GAO; Jun Feng SONG

    2005-01-01

    A novel flow-injection irreversible biamperometric method is described for the direct determination of iodide. The method is based on electrochemical oxidation of iodide at the gold electrode and the reduction of permanganate at the platinum electrode to form an irreversible biamperometric detection system. Under the applied potential difference of 0 V, in the 0.05mol/L sulfuric acid, iodide can be determined over the range 4.00×10-7-l.00×l0-5 mol/L with a sampling frequency of 120 samples per hour. The detection limit for Ⅰ- is 3.0× 10-7 mol/L and the RSD for 40 replicate determinations of 4.0×10-5 mol/L potassium iodide is 1.68%. The new method was applied to the analysis of iodide in table salt with satisfactory results.

  7. "Reagentless" flow injection determination of ammonia and urea using membrane separation and solid phase basification

    Science.gov (United States)

    Akse, J. R.; Thompson, J. O.; Sauer, R. L.; Atwater, J. E.

    1998-01-01

    Flow injection analysis instrumentation and methodology for the determination of ammonia and ammonium ions in an aqueous solution are described. Using in-line solid phase basification beds containing crystalline media. the speciation of ammoniacal nitrogen is shifted toward the un-ionized form. which diffuses in the gas phase across a hydrophobic microporous hollow fiber membrane into a pure-water-containing analytical stream. The two streams flow in a countercurrent configuration on opposite sides of the membrane. The neutral pH of the analytical stream promotes the formation of ammonium cations, which are detected using specific conductance. The methodology provides a lower limit of detection of 10 microgram/L and a dynamic concentration range spanning three orders of magnitude using a 315-microliters sample injection volume. Using immobilized urease to enzymatically promote the hydrolysis of urea to produce ammonia and carbon dioxide, the technique has been extended to the determination of urea.

  8. Determination of resveratrol in red wine by solid phase extraction-flow injection chemiluminescence method

    Institute of Scientific and Technical Information of China (English)

    2007-01-01

    A sensitive flow injection chemiluminescence method has been developed for the detection of resveratrol in red wine based on the fact that resveratrol can greatly enhance chemiluminescence reaction between KMnO4 and HCHO in sulfuric acid medium.Analytes were pre-concentrated on solid sorbents (C18 solid-phase extraction cartridges). Under the optimum conditions, the proposed method allows the measurement of resveratrol over the range of 1.32 × 10-s to 1.32 × 10-5 mol/L with a detection limit of 3.30 × 10-9 mol/L, and the relative standard deviation for 1.32 × 10-5 mol/L resveratrol (n = 11 ) is 3.8%. This method has been successfully applied for the determination of the resveratrol in red wine. Furthermore, the possible reaction mechanism was also discussed.

  9. Automatic flow injection based methodologies for determination of scavenging capacity against biologically relevant reactive species of oxygen and nitrogen.

    Science.gov (United States)

    Magalhães, Luís M; Lúcio, Marlene; Segundo, Marcela A; Reis, Salette; Lima, José L F C

    2009-06-15

    Redox reactions are the heart of numerous biochemical pathways found in cellular chemistry, generating reactive oxygen species (ROS) and reactive nitrogen species (RNS), that includes superoxide anion radical (O2-), hydrogen peroxide (H2O2), hydroxyl radical (HO), singlet oxygen ((1)O2), hypochlorite anion (OCl-), peroxynitrite anion (ONOO-) and nitric oxide radical (NO). The measurement of scavenging capacity against these reactive species presents new challenges, which can be met by flow injection analysis (FIA). In the present review several methods based on FIA and also on its predecessors computer-controlled techniques (sequential injection analysis, multisyringe flow injection analysis, multicommutated and multipumping flow systems) are critically discussed. The selectivity and applicability of the methodology, the generation and detection of the target reactive species, the benefits and limitations of automation when compared to batch methods are some of the issues addressed.

  10. Optimization and application of the gas-diffusion flow injection method for the determination of chloride

    Directory of Open Access Journals (Sweden)

    PREDRAG POLIC

    2001-09-01

    Full Text Available A selective and sensitive procedure for the fast and indirect determination of chloride by the gas-diffusion FIA method has been optimized and applied for the determination of chloride in water samples which contained different amounts of the analyte. The examined samples were: seawater, tap water and very pure water from the water-steam system of the power plant “Nikola Tesla B” in Obrenovac. Application of an amperometric detector (model LC-17A; BAS, West Lafayette, USA enables the detection limit to be decreased down to 0.05 mmol/dm3 of chloride, which corresponds to 35.5 pg, and adjustment of the acceptor flow rate and direction inside the gas-diffusion unit. In this way the optimized FIA system has excellent repeatability. For 5 mmol/dm3 it was found to be 1.11 % (n = 5. The throughput of this method is 60 samples per hour.

  11. Selective spectrofluorimetric determination of zinc in biological samples by Flow Injection Analysis (FIA)

    Energy Technology Data Exchange (ETDEWEB)

    Fernandez, P.; Perez Conde, C.; Gutierrez, A.; Camara, C. (Universidad Complutense, Madrid (Spain). Dept. de Quimica Analitica)

    1992-03-01

    The automatization of a spectrofluorimetric method for the determination of zinc at trace level is described. It is based on the formation of the fluorescent complex Zn(II)-5,7-dibromo-8-quinolinol (Zn(II)-DBQ) followed by extraction into diethylether using flow injection analysis. The optimum fluorescent emission is reached in hexamethylenetetramine (H{sub 2}MTA{sup +}/HMTA) buffer pH 6.0. A membrane phase separator was used. The calibration graph is linear up to 1.5 {mu}g/ml of Zn(II). The proposed method (detection limit 3 ng/ml) is very selective and has been successfully applied to determine Zn(II) in biological samples, tap waters and various food items. (orig.).

  12. [Determination of phenobarbital in human urine and serum using flow injection chemiluminescence].

    Science.gov (United States)

    Li, X; Niu, L C; He, X L; Song, Z H

    2012-01-01

    A sensitive chemiluminescence method, based on the enhancive effect of phenobarbital on the chemiluminescence reaction between luminol and dissolved oxygen in a flow injection system, was proposed for the determination of phenobarbital. The chemiluminescence intensity responded to the concentration of phenobarbital linearly ranging from 0.05 to 10 ng x ml(-1) with the detection limit of 0.02 ng x ml(-1) (3 sigma). At a flow rate of 2.0 ml x min(-1), a complete determination of phenobarbital, including sampling and washing, could be accomplished in 0.5 min, offering the sampling efficiency of 120 h(-1) accordingly. The method was applied successfully in an assay of PB for pharmaceutical preparations, human urine and serum without any pretreatment with recovery from 95.7 to 106.7% and RSDs of less than 3.0%.

  13. Determination of cyanide by a flow injection analysis-atomic absorption spectrometric method.

    Science.gov (United States)

    López Gómez, A V; Martínez Calatayud, J

    1998-10-01

    A new flow injection analysis (FIA) procedure is proposed for the indirect atomic absorption spectrometric determination of cyanide. The FIA manifold is based on the insertion of the sample into a distilled water carrier, then the sample flows through a solid-phase reactor filled with silver iodide entrapped in polymeric resin beads. The calibration graph is linear over the range 0.2-6.0 mg l-1 of cyanide (correlation coefficient 0.9974), the detection limit is 0.1 mg l-1, the sample throughput is 193 h-1 and the RSD is 0.8%. The method is simple, quick and more selective than other published FIA procedures. The reproducibility obtained by using different solid-phase reactors and solutions is in the range 2.2-3.1% (RSD). The method was applied to the determination of cyanide in commercial samples such as pharmaceutical formulations and industrial electrolytic baths.

  14. Reversed flow injection spectrophotometric determination of low residuals of chlorine dioxide in water using chlorophenol red

    Institute of Scientific and Technical Information of China (English)

    2002-01-01

    A novel,simple,rapid,sensitive and highly selective flow injection procedure for the spectrophotometrie determination of chlorine dioxide in the presence of other chlorine species,viz,free chlorine,chlorite,chlorate and hypoehlorite,is developed.The method is based on the discoloration reaction between chlorine dioxide and chlorophenol red and can overcome the shortcomings existed in direct speetrophotometrie determination for chlorine dioxide owing to the serious interference of free and combined chlorine.The procedure gave a linear calibration graph over the range 0-0.71 mg/L of chlorine dioxide.With a detection limit of 0.024 mg/L and a sample throughput of 60 samples/h.

  15. Flow injection fluorescence determination of dopamine using a photo induced electron transfer (PET) boronic acid derivative

    Energy Technology Data Exchange (ETDEWEB)

    Ebru Seckin, Z. [Department of Chemistry, Middle East Technical University, 06531 Ankara (Turkey); Volkan, Muervet [Department of Chemistry, Middle East Technical University, 06531 Ankara (Turkey)]. E-mail: murvet@metu.edu.tr

    2005-08-15

    An automated flow injection analysis system was developed for the fluorometric determination of dopamine in pharmaceutical injections. The method is based on the quenching effect of dopamine on m-dansylaminophenyl boronic acid (DAPB) fluorescence due to the reverse photo induced electron transfer (PET) mechanism. Effects of pH and interfering species on the determination of dopamine were examined. Calibration for dopamine, based on quenching data, was linear in the concentration range of 1.0 x 10{sup -5} to 1.0 x 10{sup -4} M. Detection limit (3 s) of the method was found to be 3.7 x 10{sup -6} M. Relative standard deviation of 1.2% (n = 10) was obtained with 1.0 x 10{sup -5} M dopamine standard solution. The proposed method was applied successfully for the determination of dopamine in pharmaceutical injection sample. The sampling rate was determined as 24 samples per hour.

  16. Optimized and validated flow-injection spectrophotometric analysis of topiramate, piracetam and levetiracetam in pharmaceutical formulations.

    Science.gov (United States)

    Hadad, Ghada M; Abdel-Salam, Randa A; Emara, Samy

    2011-12-01

    Application of a sensitive and rapid flow injection analysis (FIA) method for determination of topiramate, piracetam, and levetiracetam in pharmaceutical formulations has been investigated. The method is based on the reaction with ortho-phtalaldehyde and 2-mercaptoethanol in a basic buffer and measurement of absorbance at 295 nm under flow conditions. Variables affecting the determination such as sample injection volume, pH, ionic strength, reagent concentrations, flow rate of reagent and other FIA parameters were optimized to produce the most sensitive and reproducible results using a quarter-fraction factorial design, for five factors at two levels. Also, the method has been optimized and fully validated in terms of linearity and range, limit of detection and quantitation, precision, selectivity and accuracy. The method was successfully applied to the analysis of pharmaceutical preparations.

  17. Flow-injection chemiluminescence determination of tryptophan using galangin-potassium permanganate-polyphosphoric acid system

    Institute of Scientific and Technical Information of China (English)

    Hui Chen; Li Li; Min Zhou; Yong Jun Ma

    2008-01-01

    A high sensitive flow-injection chemiluminescence (FI-CL)method for the determination of tryptephan has been developed.The method is based on the chemiluminescence reaction of galangin-potassium perrnanganate-tryptophan in polyphosphoric acid (PPA)media.Under the optimized conditions,tryptophan was determined in the range 0.05-10 μg/mL with the detection limit (30)of 5.0× 10-3 μg/mL.The relative standard deviation (RSD)was 1.0% for 11 replicate determinations of 1.0 μg/mL tryptophan.Three synthetic samples were determined selectively with recoveries in the range from 99.6% to 102.0% in the presence of other amino acids.

  18. Rapid antioxidant capacity screening in herbal extracts using a simple flow injection-spectrophotometric system.

    Science.gov (United States)

    Mrazek, Nookrai; Watla-iad, Kanchana; Deachathai, Suwanna; Suteerapataranon, Siripat

    2012-05-01

    A simple flow injection (FI)-spectrophotometric system for the screening of antioxidant capacity in herbal extracts was developed. The analysis was based on the color disappearance due to the scavenging of 2,2-diphenyl-1-picrylhydrazyl (DPPH) radical by antioxidant compounds. DPPH and ascorbic acid were used as reagent and antioxidant standard, respectively. Effects of the DPPH concentration, DPPH flow rate, and reaction coil length on sensitivity were studied. The optimized condition provided the linear range of 0.010-0.300mM ascorbic acid with less than 5%RSD(n=10). Detection limit and quantitation limit were 0.004 and 0.013mM, respectively. Comparison of antioxidant capacity in some herbal extracts determined by the FI system and a standard method was carried out and no significant difference was obtained.

  19. Rapid high performance liquid chromatographic method for determination of clarithromycin in human plasma using amperometric detection: application in pharmacokinetic and bioequivalence studies.

    Science.gov (United States)

    Foroutan, Seyed Mohsen; Zarghi, Afshin; Shafaati, Alireza; Madadian, Babak; Abolfathi, Farshid

    2013-01-01

    A rapid, sensitive and reproducible HPLC method using amperometric detector was developed and validated for the analysis of clarithromycin in human plasma. The separation was achieved on a monolithic silica column (MZ- C8 125×4.0 mm) using acetonitrile-methanol-potassium dihydrogen phosphate buffer (40:6:54,v/v), with pH of 7.5, as the mobile phase at a flow rate of 1.5 mL/min. The assay enables the measurement of clarithromycin for therapeutic drug monitoring with a minimum quantification limit of 20 ng/mL. The method involves simple, protein precipitation procedure and analytical recovery was complete. The calibration curve was linear over the concentration range of 0.1-6 μg/mL. The coefficients of variation for inter-day and intra-day assay were found to be less than 6%. This method was used in bioequivalency and pharmacokinetic studies of the test (generic) product 2 × 500 mg clarithromycin tablets, with respect to the reference product.

  20. Determination of Trace Iodide in Water by Ion Chromatography with Integrated Amperometric Detection%积分安培检测-离子色谱法测定水中痕量碘离子

    Institute of Scientific and Technical Information of China (English)

    郭晶晶; 林冬; 李旭冉

    2016-01-01

    建立了积分安培检测-离子色谱法测定水中痕量碘离子的方法,在0~500μg/L浓度范围内线性良好,实验表明该法检出限低(0.15μg/L),精密度高(相对标准偏差小于2.0%),准确性好(地表水样品和地下水样品的加标回收率分别为97.0%和96.7%),适宜测定地表水和地下水中痕量的碘离子,对于成分复杂,有机物含量高的生活污水和工业废水可采取稀释等预处理措施后再进行分析,是一种易于广泛推广使用的新型分析方法。%A method for determination of trace iodide in water by ion chromatography with integrated amperometric detection was established .A good linear relationship was achieved in the range of 0~500 μg/L.The limit of detection was low (0.15 μg/L).The precision was high (relative standard deviation less than 2.0%).The accuracy was good with the recovery rate of 97.0% and 96.7% of surface water and groundwater samples .This method is applicable to determine trace iodide of surface water and groundwater . The sewage and industrial wastewater with complicated composition and high organic matter can be determined after pretreatment measures such as dilution .Ion chromatography with integrated amperometric detection is a kind of new analysis method of easy to be widely used .

  1. Ion-exchange chromatography combined with direct current amperometric detection at CuNPs/reduced graphene oxide-chitosan composite film modified electrode for determination of monosaccharide composition of polysaccharides from Phellinus igniarius.

    Science.gov (United States)

    Xi, Lingling; Wang, Fengli; Zhu, Zuoyi; Huang, Zhongping; Zhu, Yan

    2014-02-01

    A novel Cu nanoparticles/reduced graphene oxide-chitosan (CuNPs/r-GO-chitosan) composite film modified glassy carbon electrode (GCE) was fabricated by dispersing CuNPs uniformly on a stable r-GO-chitosan thin film through electrodeposition process. The modified electrode was characterized by cyclic voltammetry, scanning electron microscopy (SEM) and electrochemical impedance spectroscopy (EIS), and exhibited efficiently electrocatalytic oxidation toward monosaccharides with high stability. The good electrocatalytic activity of this modified electrode might be attributed to the synergistic effect of r-GO and CuNPs, and the stability might be attributed to the r-GO and chitosan thin matrix film. When the CuNPs/r-GO-chitosan/GCE was used as an electrochemical sensor in high performance anion exchange chromatography-direct current amperometric detection (HPAEC-DC) flowing system for the determination of monosaccharides under constant working potential of +0.55 V, the detection limits (S/N=3) ranged from 0.006 to 0.02 mg L(-1) for the analyzed sugars, and the dynamic linear ranges spanned from 0.02 to 500 mg L(-1). The proposed method has been applied for the determination of monosaccharide composition of crude polysaccharides from phellinus igniarius real samples, and the results were satisfactory.

  2. Universal Signal Conditioning System for Amperometric Sensors

    Directory of Open Access Journals (Sweden)

    CRISTEA, D. G.

    2012-02-01

    Full Text Available In this article the research for developing whole-cell biochips has been presented using both bioluminescent and electrochemical methods. The research was on integrating an electrode cell with both electrochemical and bioluminescent detection using a single VLSI chip. The authors have investigated the signal conditioning system that can work with any kind of amperometric and bioluminescent sensor. During this research the authors focused on the analog front-end unit. The work includes investigating the electronic model for simulation for an electrochemical cell and conceiving a fully integrated 8X8 electrochemical sensor array. The authors are focusing on signal conditioning system and its functionality. The main concern for the authors was to maintain the complexity and the number of electronic devices as low as possible.

  3. Catalytic activity of iron hexacyanoosmate(II) towards hydrogen peroxide and nicotinamide adenine dinucleotide and its use in amperometric biosensors

    Energy Technology Data Exchange (ETDEWEB)

    Kotzian, Petr; Janku, Tereza [Department of Analytical Chemistry, University of Pardubice, Nam. Cs. Legii 565, CZ-532 10 Pardubice (Czech Republic); Kalcher, Kurt [Institute of Chemistry - Analytical Chemistry, Karl-Franzens University, Universitaetsplatz 1, A-8010 Graz (Austria); Vytras, Karel [Department of Analytical Chemistry, University of Pardubice, Nam. Cs. Legii 565, CZ-532 10 Pardubice (Czech Republic)], E-mail: karel.vytras@upce.cz

    2007-09-19

    Hydrogen peroxide and nicotinamide adenine dinucleotide (NADH) may be determined amperometrically using screen-printed electrodes chemically modified with iron(III) hexacyanoosmate(II) (Osmium purple) in flow injection analysis (FIA). The determination is based on the exploitation of catalytic currents resulting from the oxidation/reduction of the modifier. The performance of the sensor was characterized and optimized by controlling several operational parameters (applied potential, pH and flow rate of the phosphate buffer). Comparison has been made with analogous complexes of ruthenium (Ruthenium purple) and iron (Prussian blue). Taking into account the sensitivity and stability of corresponding sensors, the best results were obtained with the use of Osmium purple. The sensor exhibited a linear increase of the amperometric signal with the concentration of hydrogen peroxide in the range of 0.1-100 mg L{sup -1} with a detection limit (evaluated as 3{sigma}) of 0.024 mg L{sup -1} with a R.S.D. 1.5% for 10 mg L{sup -1} H{sub 2}O{sub 2} under optimized flow rate of 0.4 mL min{sup -1} in 0.1 M phosphate buffer carrier (pH 6) and a working potential of +0.15 V versus Ag/AgCl. Afterwards, a biological recognition element - either glucose oxidase or ethanol dehydrogenase - was incorporated to achieve a sensor facilitating the determination of glucose or ethanol, respectively. The glucose sensor gave linearity between current and concentration in the range from 1 to 250 mg L{sup -1} with a R.S.D. 2.4% for 100 mg L{sup -1} glucose, detection limit 0.02 mg L{sup -1} (3{sigma}) and retained its original activity after 3 weeks when stored at 6 deg. C. Optimal parameters in the determination of ethanol were selected as: applied potential +0.45 V versus Ag/AgCl, flow rate 0.2 mL min{sup -1} in 0.1 M phosphate buffer carrier (pH 7). Different structural designs of the ethanol sensor were tested and linearity obtained was up to 1000 mg L{sup -1} with a maximum R.S.D. of 5

  4. Wireless Amperometric Neurochemical Monitoring Using an Integrated Telemetry Circuit

    Science.gov (United States)

    Roham, Masoud; Halpern, Jeffrey M.; Martin, Heidi B.; Chiel, Hillel J.

    2015-01-01

    An integrated circuit for wireless real-time monitoring of neurochemical activity in the nervous system is described. The chip is capable of conducting high-resolution amperometric measurements in four settings of the input current. The chip architecture includes a first-order ΔΣ modulator (ΔΣM) and a frequency-shift-keyed (FSK) voltage-controlled oscillator (VCO) operating near 433 MHz. It is fabricated using the AMI 0.5 μm double-poly triple-metal n-well CMOS process, and requires only one off-chip component for operation. Measured dc current resolutions of ~250 fA, ~1.5 pA, ~4.5 pA, and ~17 pA were achieved for input currents in the range of ±5, ±37, ±150, and ±600 nA, respectively. The chip has been interfaced with a diamond-coated, quartz-insulated, microneedle, tungsten electrode, and successfully recorded dopamine concentration levels as low as 0.5 μM wirelessly over a transmission distance of ~0.5 m in flow injection analysis experiments. PMID:18990633

  5. Prediction of wastewater quality using amperometric bioelectronic tongues.

    Science.gov (United States)

    Czolkos, Ilja; Dock, Eva; Tønning, Erik; Christensen, Jakob; Winther-Nielsen, Margrethe; Carlsson, Charlotte; Mojzíková, Renata; Skládal, Petr; Wollenberger, Ulla; Nørgaard, Lars; Ruzgas, Tautgirdas; Emnéus, Jenny

    2016-01-15

    Wastewater samples from a Swedish chemi-thermo-mechanical pulp (CTMP) mill collected at different purification stages in a wastewater treatment plant (WWTP) were analyzed with an amperometric enzyme-based biosensor array in a flow-injection system. In order to resolve the complex composition of the wastewater, the array consists of several sensing elements which yield a multidimensional response. We used principal component analysis (PCA) to decompose the array's responses, and found that wastewater with different degrees of pollution can be differentiated. With the help of partial least squares regression (PLS-R), we could link the sensor responses to the Microtox® toxicity parameter, as well as to global organic pollution parameters (COD, BOD, and TOC). From investigating the influences of individual sensors in the array, it was found that the best models were in most cases obtained when all sensors in the array were included in the PLS-R model. We find that fast simultaneous determination of several global environmental parameters characterizing wastewaters is possible with this kind of biosensor array, in particular because of the link between the sensor responses and the biological effect onto the ecosystem into which the wastewater would be released. In conjunction with multivariate data analysis tools, there is strong potential to reduce the total time until a result is yielded from days to a few minutes.

  6. O-(β-hydroxyethylrutosides determination by micellar flow injection (FI-spectrofluorimetry

    Directory of Open Access Journals (Sweden)

    Cecilia Mariana Peralta

    2014-12-01

    Full Text Available A simple, eco-friendly, sensitive and economic flow injection spectrofluorimetric method was developed for the determination of O-(β-hydroxyethylrutosides. The procedure was based on the use of an anionic surfactant such as sodium dodecyl sulfate to provide an appreciable O-(β-hydroxyethylrutosides fluorescence enhancement, increasing considerably the sensitivity of detection. All the variables affecting the fluorescence intensity were studied and optimized. The flow rate was 5 mL/min with detection at 450 nm (after excitation at 346 nm. A linear correlation between drug amount and peak area was established for O-(β-hydroxyethylrutosides in the range of 0.01–200 µg/mL with a detection limit of 0.001 µg/mL (s/n=3. Validation processes were performed by recovering studies with satisfactory results. The new methodology can be employed for the routine analysis of O-(β-hydroxyethylrutosides in bulks as well as in commercial formulations.

  7. Automated flow-injection method for cadmium determination with pre-concentration and reagent preparation on-line

    Directory of Open Access Journals (Sweden)

    María S. Di Nezio

    2005-02-01

    Full Text Available The spectrophotometric determination of Cd(II using a flow injection system provided with a solid-phase reactor for cadmium preconcentration and on-line reagent preparation, is described. It is based on the formation of a dithizone-Cd complex in basic medium. The calibration curve is linear between 6 and 300 µg L-1 Cd(II, with a detection limit of 5.4 µg L-1, an RSD of 3.7% (10 replicates in duplicate and a sample frequency of 11.4 h-1. The proposed method was satisfactorily applied to the determination of Cd(II in surface, well and drinking waters.

  8. On-line focusing of 5-hydroxy-tryptamine type 3 receptor antagonists via the combination of field-enhanced sample injection and dynamic pH junction in capillary electrophoresis with amperometric detection.

    Science.gov (United States)

    Li, Libo; Xu, Lei; Huang, Jianshe; You, Tianyan

    2014-02-28

    In the present work, an on-line dual focusing technique based on field-enhance sample injection (FASI) and dynamic pH junction (DypH) was developed for the analysis of two 5-hydroxy-tryptamine type 3 receptor (5-HT3) antagonists ondansetron (Ond) and tropisetron (Tro) by capillary electrophoresis with amperometric detection (CE-AD) system. By preparing the sample in a lower conductivity (FASI condition) and lower pH value (DypH condition) matrix relative to the background electrolyte (BGE) solution, a simple and effective dual focusing approach, FASI-DypH was achieved. In this stacking mode, a large amount of analytes could be electrokinetically injected into the capillary and stacked at the boundary of the sample and the BGE zone as a result of deprotonation and decrease in the electric field. Effects of separation, detection and FASI-DypH focusing conditions were investigated in detail. Under the optimum conditions, good separation for Ond and Tro was achieved within 8min. In comparison with the conventional CE-AD analysis method, the present dual focusing technique enabled the enhancement factors in terms of peak heights to reach 357-fold and 345-fold for Ond and Tro, respectively. The limits of detection (LODs) (S/N=3) for Ond and Tro were 2nM and 5nM, respectively. The intraday and interday repeatabilities (RSDs) were less than 4.5% and 2.9% for peak height and migration time, respectively. The proposed method was successfully applied for the analysis of Ond and Tro in human urine sample. Copyright © 2014 Elsevier B.V. All rights reserved.

  9. Flow injection-chemiluminescence determination of ascorbic acid based on luminol–ferricyanide–gold nanoparticles system

    Energy Technology Data Exchange (ETDEWEB)

    Dong, Yong Ping, E-mail: dongyp@ahut.edu.cn [School of chemistry and chemical engineering, Anhui University of Technology, Maanshan, China, 243002 (China); Gao, Ting Ting; Chu, Xiang Feng; Chen, Jun [School of chemistry and chemical engineering, Anhui University of Technology, Maanshan, China, 243002 (China); Wang, Cheng Ming, E-mail: chmwang@ustc.edu.cn [Hefei National Laboratory for Physical Science at the Microscale, University of Science and Technology of China, Hefei, China, 230026 (China)

    2014-10-15

    A novel flow-injection chemiluminescence (CL) method for the determination of ascorbic acid (AA) is proposed, based upon its enhancing effect on the CL reaction of luminol with ferricyanide catalyzed by gold nanoparticles in alkaline solution. Different sizes gold nanoparticles exhibited different catalyzing effect towards luminol CL and 38 nm gold nanoparticles exhibited the best enhancing effect. Under the optimal experimental conditions, a linear relationship was obtained between the CL intensity and the concentration of ascorbic acid in the range of 1.0×10{sup −10}–1.0×10{sup −6} mol L{sup −1}. The detection limit was 2.0×10{sup –11} mol {sup −1} and the relative standard deviation for 1.0×10{sup −6} mol L{sup −1} ascorbic acid was 0.71% (n=10). This method has been successfully applied in the determination of ascorbic acid in several real samples. - Highlights: • Gold nanoparticles could enhance luminol–K{sub 3}Fe(CN){sub 6} CL signal. • 38 nm gold nanoparticles exhibited the best catalyzing effect. • Ascorbic acid could further enhance luminol–K{sub 3}Fe(CN){sub 6}–gold nanoparticles CL. • Ascorbic acid could be detected sensitively based on its enhancing effect.

  10. Flow injection analysis of ketoprofen based on the order transform second chemiluminescence reaction

    Science.gov (United States)

    Zhuang, Yafeng; Cao, Guiping; Ge, Chuanqin

    2012-01-01

    This paper explores an order-transform-second-chemiluminescence (OTSCL) method combining the flow injection technique for the determination of ketoprofen. When ketoprofen solution was injected into the mixture after the end of the reaction of alkaline luminol and sodium periodate or sodium periodate solution was injected into the reaction mixture of ketoprofen and alkaline luminol, a new chemiluminescence (CL) reaction was initiated and strong CL signal was detected. A mechanism for the OTSCL has been proposed on the basis of the chemiluminescence kinetic characteristic, UV-visible absorption and chemiluminescent spectra. Under optimal experimental conditions, the CL response is proportional to the concentration of ketoprofen over the range of 2.0 × 10 -7 to 1.0 × 10 -5 mol/L with a correlation coefficient of 0.9950 and a detection limit of 8.0 × 10 -9 mol/L (3 σ). The relative standard deviation for 11 repetitive determinations of 1.0 × 10 -6 mol/L ketoprofen is 2.9%. The utility of this method was demonstrated by determining ketoprofen in pharmaceutical formulations without interference from its potential impurities.

  11. Determination of formaldehyde in Brazilian alcohol fuels by flow-injection solid phase spectrophotometry

    Energy Technology Data Exchange (ETDEWEB)

    Teixeira, Leonardo S.G.; Leao, Elsimar S.; Dantas, Alailson F.; Pinheiro, Heloisa L.C.; Costa, Antonio C.S.; De Andrade, Jailson B. [Instituto de Quimica-Universidade Federal da Bahia, Campus Universitario de Ondina, 40.170-280-Salvador, Bahia (Brazil)

    2004-10-20

    In this work, a solid phase spectrophotometric method in association with flow injection analysis for formaldehyde determination has been developed with direct measurement of light-absorption in C{sub 18} material. The 3,5-diacetyl-1,4-dihydrolutidine produced from the reaction between formaldehyde and fluoral P was quantitatively retained on C{sub 18} support and the spectrophotometric detection was performed simultaneously at 412nm. The retained complex was quickly eluted from C{sub 18} material with the eluent stream consisting of a 50% (v/v) ethanol solution. The results showed that the proposed method is simple, rapid and the analytical response is linear in the concentration range of 0.050-1.5mgL{sup -1}. The limit of detection was estimated as 30{mu}mgL{sup -1} and the R.S.D. 2.2% using a sample volume of 625{mu}mL. The system presented an analytical throughput of 20 determinations per hour. The method was successfully applied in the determination of formaldehyde in ethanol fuel.

  12. Determination of formaldehyde in Brazilian alcohol fuels by flow-injection solid phase spectrophotometry.

    Science.gov (United States)

    Teixeira, Leonardo S G; Leão, Elsimar S; Dantas, Alaílson F; Pinheiro, Heloísa L C; Costa, Antonio C S; de Andrade, Jailson B

    2004-10-20

    In this work, a solid phase spectrophotometric method in association with flow injection analysis for formaldehyde determination has been developed with direct measurement of light-absorption in C(18) material. The 3,5-diacetyl-1,4-dihydrolutidine produced from the reaction between formaldehyde and fluoral P was quantitatively retained on C(18) support and the spectrophotometric detection was performed simultaneously at 412nm. The retained complex was quickly eluted from C(18) material with the eluent stream consisting of a 50% (v/v) ethanol solution. The results showed that the proposed method is simple, rapid and the analytical response is linear in the concentration range of 0.050-1.5mgL(-1). The limit of detection was estimated as 30mugL(-1) and the R.S.D. 2.2% using a sample volume of 625muL. The system presented an analytical throughput of 20 determinations per hour. The method was successfully applied in the determination of formaldehyde in ethanol fuel.

  13. Screen-printed sensor for batch and flow injection potentiometric chromium(VI) monitoring

    Energy Technology Data Exchange (ETDEWEB)

    Sanchez-Moreno, Raul A.; Gismera, M.J.; Sevilla, M.T.; Procopio, Jesus R. [Facultad de Ciencias, Universidad Autonoma de Madrid, Departamento de Quimica Analitica y Analisis Instrumental, Madrid (Spain)

    2010-05-15

    A disposable screen-printed electrode was designed and evaluated for direct detection of chromium(VI) in batch and flow analysis. The carbon screen-printed electrode was modified with a graphite-epoxy composite. The optimal graphite-epoxy matrix contains 37.5% graphite powder, 12.5% diphenylcarbohydrazide, a selective compound for chromium(VI), and 50% epoxy resin. The principal analytical parameters of the potentiometric response in batch and flow analysis were optimized and calculated. The screen-printed sensor exhibits a response time of 20 {+-} 1 s. In flow analysis, the analytical frequency of sampling is 70 injections per hour using 0.1 M NaNO{sub 3} solution at pH 3 as the carrier, a flow rate of 2.5 mL.min{sup -1}, and an injection sample volume of 0.50 mL. The sensor shows potentiometric responses that are very selective for chromium(VI) ions and optimal detection limits in both static mode (2.1 x 10{sup -7} M) and online analysis (9.4 x 10{sup -7} M). The disposable potentiometric sensor was employed to determine toxicity levels of chromium(VI) in mineral, tap, and river waters by flow-injection potentiometry and batch potentiometry. Chromium(VI) determination was also carried out with successful results in leachates from municipal solid waste landfills. (orig.)

  14. The use of differential measurements with a glucose biosensor for interference compensation during glucose determinations by flow injection analysis.

    Science.gov (United States)

    McGrath, M J; Iwuoha, E I; Diamond, D; Smyth, M R

    1995-01-01

    A novel detection system for the determination of glucose in the presence of clinically important interferents, based on the use of dual sensors and flow-injection analysis (FIA), is described. The normalisation methodology involves measurement of the interference signal at a reference sensor; this signal can then be subtracted from the glucose sensor signal (post-run) to give a corrected measurement of the glucose concentration. The detection system consists of a thin layer with dual glassy carbon working electrodes. One electrode was surface modified to act as a glucose biosensor by immobilisation of glucose oxidase (GOx) (from Aspergillus niger) with 1% glutaraldehyde and bovine serum albumin. The second electrode (glucose oxidase omitted) was utilised to measure the interference signal responding only to electroactive species present in the injected sample. A computer controlled multichannel potentiostat was used for potential application and current monitoring duties. The sensor responses were saved in ASCII format to facilitate post-run analysis in Microsoft Excel. Cyclic voltammetry (CV) was utilised to investigate the manner in which the interference signal contributed to the total signal obtained at the biosensor in the presence of glucose. The kinetics parameters Imax and the apparent Michaelis-Menten constant, K'm, were calculated for the sensor operating under flow-injection conditions.

  15. Construcción de un Inmunosensor Amperométrico utilizando Apirasa de Solanum tuberosum para la Detección de Esquistosomiasis Construction of an Amperometric Immunosensor using Solanum tuberosum potato Apyrase for the Detection of Schistosomiasis

    Directory of Open Access Journals (Sweden)

    Ninoska I Bojorge Ramírez

    2009-01-01

    Full Text Available Este trabajo presenta el desarrollo de un inmunosensor amperométrico composito a base de una proteína de origen vegetal para la determinación de antí-anticuerpo de S. mansoni. El inmunosensor consiste en una matriz electródica rígida construida con grafito y resina epoxi en la que se inmoviliza covalentemente la Apirasa. La estrategia de inmovilización se basa en silanización de la matriz compósita con 3-aminopropilsilano (3-APTES y su activación mediante glutaraldehído. La inmovilización fue monitoreada mediante voltaamperometría cíclica en Fe(CN6(4-/Fe(CN6³, obteniéndose una respuesta cuasi-reversible del inmunosensor y muy estable en el tiempo. La inmovilización también fue caracterizada mediante ángulos de contactos y microscopía electrónica de barrido. Estas cualidades son aprovechables para la determinación clínica de esquistosomiasis dada la rapidez y sensibilidad de respuesta.This paper presents the development of an amperometric composites inmunosensor based on a vegetable protein for the determination of anti-Ac S. mansoni. The inmunosensor consists of a rigid matrix built with graphite and epoxy resin in which immobilizes covalently the Apyrase. The strategy of immobilization is based in silanization of the matrix composites with 3-Aminopropyltriethoxysilane (3-APTES and its activation by glutaraldehyde. The detection was monitored by cyclic voltammetry Fe(CN6(4-/ Fe(CN6³, obtaining a response quasi-reversible of the immunosensor and very stable over time. The immobilization was also characterized by angles contacts and scanning electron microscopy. These qualities are useful for determination clinical of schistosomiasis given the speed of response and sensitivity.

  16. Simultaneous amperometric detection of ascorbic acid and antioxidant capacity in orange, blueberry and kiwi juice, by a telemetric system coupled with a fullerene- or nanotubes-modified ascorbate subtractive biosensor.

    Science.gov (United States)

    Barberis, Antonio; Spissu, Ylenia; Fadda, Angela; Azara, Emanuela; Bazzu, Gianfranco; Marceddu, Salvatore; Angioni, Alberto; Sanna, Daniele; Schirra, Mario; Serra, Pier Andrea

    2015-05-15

    Four fullerenes- or nanotubes-modified graphite sensor-biosensor systems (SBs), coupled with a dual-channel telemetric device, based on an ascorbate oxidase (AOx) biosensor, were developed for on line simultaneous amperometric detection of ascorbic acid (AA) and antioxidant capacity in blueberry, kiwi and orange juice. Fullerene C60 (FC60), fullerene C70 (FC70), single-walled carbon nanotubes (SWCN) and multi-walled carbon nanotubes (MWCN) increased the sensitivity of graphite toward AA and phenols 1.2, 1.5, 5.1 and 5.1 times respectively. Fullerenes combined with AOx improved the selectivity toward AA more than nanotubes, being able to hold a higher number of AOx molecules on the biosensor surface. The SBs work at an applied potential of +500 mV, in a concentration range between the LOD and 20 μM, with a response time of two minutes. The LOD is 0.10, 0.13, 0.20 and 0.22 μM for SBs modified with FC60, FC70, SWCN and MWCN respectively. Biosensors register lower AA currents than the sensors due to the enzyme capability to oxidize AA before it reaches the transductor surface. Phenols currents registered by sensors and biosensors did not differ. Based on the difference between sensor and biosensor recorded currents a AA selectivity index was developed as an indicator of specificity toward AA and of the capacity to distinguish between AA and phenols contribution to the antioxidant capacity. This value is almost zero for fullerene-modified SBs, 0.13 and 0.22 for SWCN- and MWCN-modified SBs respectively. The results of juices analysis performed with SBs were in accordance with reference methods.

  17. Determination of sulfate in the wet-process of phosphoric acid by reverse flow injection

    Directory of Open Access Journals (Sweden)

    Wenhui Shi

    2014-01-01

    Full Text Available An improved method based on reverse flow injection is proposed for determining sulfate concentration in the wet-process of phosphoric acid (WPA. The effect of reagent composition, flow rate, temperature, acid concentration, length of the reaction coil, and linear response range on the flow system is discussed in detail. Optimal conditions are established for determining sulfate in the WPA samples. Baseline drift is avoided by a periodic washing step with EDTA in an alkaline medium. A linear response is observed within a range of 20 - 360 mg L-1, given by the equation A = 0.0020C (mg L-1 + 0.0300, R² = 0.9991. The detection limit of the proposed method for sulfate analysis is 3 mg L-1, and the relative standard deviation (n = 12 of sulfate absorbance peak is less than 1.60%. This method has a rate of up to 29 samples per hour, and the results compare well with those obtained with gravimetric method.

  18. A spectrophotometric flow injection system for streptomycin determination in veterinary samples

    Science.gov (United States)

    Frugeri, Pedro Marcos; Lago, Ayla Campos do; Wisniewski, Célio; Luccas, Pedro Orival

    2014-01-01

    In this work a spectrophotometric flow injection analysis system for streptomycin determination in veterinary samples, is being proposed. The method is based on streptomycin alkaline hydrolysis that forms guanidine, followed by the reaction with Fe(II). The colored product has absorption peak at 520 nm. To evaluate and optimize the system parameters, chemometrics tools, such as factorial design, Pareto chart and Doelhert design, were used. The veterinary samples are diluted in water and introduced in the FIA system, therefore no sample preparation is required. The optimized system presented: linear range of 60 up to 1000 mg L-1, limit of detection of 18 mg L-1 and sampling rate of 36 readings per hour. The precision was checked and the CV for veterinary sample readings were always less than 6.5%. The accuracy was studied by comparison with chromatographic method, thus, five samples of pharmaceutical veterinary were determined by HPLC and by the proposed method, and the results are in agreement (t-test, p = 0.05).

  19. Ultra-sensitive Flow Injection Analysis (FIA) determination of calcium in ice cores at ppt level.

    Science.gov (United States)

    Traversi, R; Becagli, S; Castellano, E; Maggi, V; Morganti, A; Severi, M; Udisti, R

    2007-07-02

    A Flow Injection Analysis (FIA) spectrofluorimetric method for calcium determination in ice cores was optimised in order to achieve better analytical performances which would make it suitable for reliable calcium measurements at ppt level. The method here optimised is based on the formation of a fluorescent compound between Ca and Quin-2 in buffered environment. A careful evaluation of operative parameters (reagent concentration, buffer composition and concentration, pH), influence of interfering species possibly present in real samples and potential favourable effect of surfactant addition was carried out. The obtained detection limit is around 15 ppt, which is one order of magnitude lower than the most sensitive Flow Analysis method for Ca determination currently available in literature and reproducibility is better than 4% for Ca concentrations of 0.2 ppb. The method was validated through measurements performed in parallel with Ion Chromatography on 200 samples from an alpine ice core (Lys Glacier) revealing an excellent fit between the two chemical series. Calcium stratigraphy in Lys ice core was discussed in terms of seasonal pattern and occurrence of Saharan dust events.

  20. Flow-injection Spectrophotometric Determination of Uric Acid in Urine via Prussian Blue Reaction

    Institute of Scientific and Technical Information of China (English)

    WASEEM Amir; YAQOOB Mohammad; NABI Abdul; MURTAZA Ghulam; HUSSAIN Izhar

    2011-01-01

    A simple and sensitive flow injection(FI)spectrophotometric method was reported for the determination of uric acid based on the reduction of Fe(Ⅲ)/ferricyanide in the presence of uric acid.The in situ reduced ions reacted with unreduced portion of ferricyanide/Fe(Ⅲ)to form soluble Prussian blue,which was monitored at an absorption wavelength of 735 nm.The optimized conditions allow a linear calibration graph in a concentration range of 1-100μmol/L.The relative standard deviation was in a range of 0.5%-2.5%,with a detection limit(3σ blank)of 0.3 μmol/L and a sampling frequency of 60 injection/h was obtained.The effect of common substances present in human physiological fluids on the determination of uric acid was examined.The method was applied to determining uric acid in human urine samples with the recoveries in a range of 96%-105%.The results agree well with those by spectrophotometric reference method at a confidence level of 95%.Spectrophotometric procedures for uric acid determination in clinical samples were reviewed briefly.

  1. Photoelectrocatalytic determination of NADH in a flow injection system with electropolymerized methylene blue

    Energy Technology Data Exchange (ETDEWEB)

    Dilgin, Yusuf, E-mail: ydilgin@yahoo.co [Canakkale Onsekiz Mart University, Science and Art Faculty, Department of Chemistry, TR-17100 Canakkale (Turkey); Dilgin, Didem Giray [Canakkale Onsekiz Mart University, Biga Vocational College, TR-17200 Biga Canakkale (Turkey); Ege University, Science Faculty, Department of Chemistry, TR-35100 Bornova/Izmir (Turkey); Dursun, Zekerya; Goekcel, H. Ismet [Ege University, Science Faculty, Department of Chemistry, TR-35100 Bornova/Izmir (Turkey); Gligor, Delia [Department of Environmental Physics, Chemistry and Engineering, ' Babes-Bolyai' University, 30 Fantanele St., 400294 Cluj-Napoca (Romania); Bayrak, Burcu; Ertek, Bensu [Canakkale Onsekiz Mart University, Science and Art Faculty, Department of Chemistry, TR-17100 Canakkale (Turkey)

    2011-01-01

    It was firstly described that a glassy carbon electrode electropolymerized with methylene blue shows an efficient photoelectrocatalytic activity towards NADH oxidation in a phosphate buffer solution (pH 7.0). In order to perform the photoelectrocatalytic determination of NADH in a flow injection analysis (FIA) system, a home-made flow electrochemical cell with a suitable transparent window for the irradiation of the electrode surface was constructed. The currents obtained from the photoamperometric measurements in the FIA system at optimum conditions (flow rate of carrier solution, 1.3 mL min{sup -1}; transmission tubing length, 10 cm; injection volume, 100 {mu}L; and constant applied potential, +150 mV vs. Ag/AgCl) were linearly dependent on the NADH concentration and linear calibration curves were obtained in the range of 1.0 x 10{sup -7}-2.0 x 10{sup -4} M. The detection limit was found to be 4.0 x 10{sup -8} M for photoamperometric determination of NADH.

  2. Flow-injection determination of isoniazid using sodium dichloroisocyanurate- and trichloroisocyanuric acid-luminol chemiluminescence systems.

    Science.gov (United States)

    Safavi, A; Karimi, M A; Hormozi Nezhad, M R

    2004-06-01

    A chemiluminescent (CL) method for the determination of isoniazid is described. The method is based on the CL generated during the oxidation of luminol by sodium dichloroisocyanurate (SDCC) and trichloroisocyanuric acid (TCCA) in alkaline medium. It was found that isoniazid greatly enhances this CL intensity when present in the luminol solution. Based on this observation, a new flow-injection CL method for the determination of isoniazid has been proposed in this paper. The detection limits were 2 and 3 ng ml(-1) isoniazid for the SDCC-luminol and TCCA-luminol CL systems, respectively. The relative CL intensity was linear with the isoniazid concentration in the range of 4-100 and 100-200 ng ml(-1) for the SDCC-luminol CL system, and 6-200 and 200-1000 ng ml(-1) for the TCCA-luminol CL system. The results obtained for the assay of pharmaceutical preparations compared well with those obtained by the official methods and demonstrated good accuracy and precision.

  3. A new sensitive flow-injection chemiluminescence method for the determination of H(2)-receptor antagonists.

    Science.gov (United States)

    Tang, Yu-Hai; Wang, Nan-Nan; Xiong, Xun-Yu; Xiong, Feng-Mei; Sun, Si-Juan

    2007-01-01

    Based on the chemiluminescence (CL) intensity generated from the potassium ferricyanide [K(3)Fe(CN)(6)]-rhodamine 6G system in sodium hydroxide (NaOH) medium, a new sensitive flow-injection chemiluminescence (FI-CL) method has been developed, validated and applied for the determination of three kinds of H(2)-receptor antagonists: cimetidine (CIMT), ranitidine (RANT) hydrochloride and famotidine (FAMT). Under the optimum conditions, the linear range for the determination was 1.0 x 10(-9)-7.0 x 10(-5) g/ml for CIMT, 1.0 x 10(-9)-5.0 x 10(-5) g/mL for RANT hydrochloride and 5.0 x 10(-9)-7.0 x 10(-5) g/mL for FAMT. During 11 repeated measurements of 1.0 x 10(-6) g/mL sample solutions, the relative standard deviations (RSDs) were all <5%. The detection limit was 8.56 x 10(-10) g/mL for CIMT, 8.69 x 10(-10) g/mL for RANT hydrochloride and 2.35 x 10(-9) g/mL for FAMT (S:N = 3). This method has been successfully implemented for the analysis of H(2)-receptor antagonists in pharmaceuticals.

  4. Selective and Sensitive Chemiluminescence Determination of MCPB: Flow Injection and Liquid Chromatography.

    Science.gov (United States)

    Meseguer-Lloret, Susana; Torres-Cartas, Sagrario; Catalá-Icardo, Mónica; Gómez-Benito, Carmen

    2016-02-01

    Two new chemiluminescence (CL) methods are described for the determination of the herbicide 4-(4-chloro-o-tolyloxy) butyric acid (MCPB). First, a flow injection chemiluminescence (FI-CL) method is proposed. In this method, MCPB is photodegraded with an ultraviolet (UV) lamp and the photoproducts formed provide a great CL signal when they react with ferricyanide in basic medium. Second, a high-performance liquid chromatography chemiluminescence (HPLC-CL) method is proposed. In this method, before the photodegradation and CL reaction, the MCPB and other phenoxyacid herbicides are separated in a C18 column. The experimental conditions for the FI-CL and HPLC-CL methods are optimized. Both methods present good sensitivity, the detection limits being 0.12 µg L(-1) and 0.1 µg L(-1) (for FI-CL and HPLC-CL, respectively) when solid phase extraction (SPE) is applied. Intra- and interday relative standard deviations are below 9.9%. The methods have been satisfactorily applied to the analysis of natural water samples. FI-CL method can be employed for the determination of MCPB in simple water samples and for the screening of complex water samples in a fast, economic, and simple way. The HPLC-CL method is more selective, and allows samples that have not been resolved with the FI-CL method to be solved.

  5. Determination of arsenic in a nickel alloy by flow injection hydride generation atomic absorption spectrometry

    Science.gov (United States)

    Hanna, C. P.; Tyson, J. F.; Offley, S. G.

    1992-08-01

    The development of a method for the direct determination of trace arsenic quantities in nickel alloy digests, by flow injection hydride generation atomic absorption spectrometry, is described. An optimization study of the manifold and chemical parameters produced system performance, in terms of tolerance of the nickel matrix and sensitivity, such that matrix removal and pre-reduction of As(V) to As (III) prior to arsine generation were eliminated. Full recovery of the As(V) signal from a solution containing 5 ng ml -1 in the presence of 60 μg ml -1 nickel was obtained. Validation of the method was achieved by analyzing a British Chemical Standard (BCS) Certified Reference Material (CRM) #346 IN nickel alloy containing arsenic at a concentration of 50 μg g -1. Following dissolution in nitric and hydrofluoric acids by a microwave assisted procedure, the only subsequent preparation required was dilution by the appropriate factor. Up to 60 injections h -1 may be made, with a detection limit of 0.5 ng ml -1 arsenic (250 pg absolute) as As(V) in a 500 μl sample. The peak height characteristic concentration is 0.46 ng ml -1, with a relative standard deviation of 3.5% for a 10 ng ml -1 As(V) standard ( n = 6).

  6. Sequential flow injection determination of chlorine species using a triiodide-selective electrode detector.

    Science.gov (United States)

    Saad, Bahruddin; Wai, Wan Tatt; Ali, Abdussalam Salhin M; Saleh, Muhammad Idiris

    2006-01-01

    A flow injection analysis (FIA) method for the determination of four residual chlorine species, namely combined available chlorine (CAC), free available chlorine (FAC), total available chlorine (TAC) and chlorite (ClO2-) was developed using a flow-through triiodide-selective electrode as a detector. An important strategy of speciation studies utilized the kinetic discrimination of reactions between the CAC and FAC with Fe2+, which was applied to the speciation of FAC, CAC and TAC. The speciation of available chlorine species and chlorite (an oxychlorine species) was achieved by using the same set-up, but using flow streams of different pH. The effects of the pH of the carrier stream, the flow rate and the sample volume were studied. The method exhibited linearity from 2.8 x 10(-6) to 2.8 x 10(-4) M active chlorine (expressed as OCl-) with a detection limit of 1.4 x 10(-6) M. The selectivity of the method was studied by examining the minimum pH for the oxidation of iodide by other oxidants, and also by assessing the potentiometric selectivity coefficients. The proposed method was successfully applied to the determination of chlorine species in tap water, and disinfecting formulations where good agreement occurred between the proposed and standard methods were found.

  7. Flow injection colorimetric method using acidic ceric nitrate as reagent for determination of ethanol.

    Science.gov (United States)

    Pinyou, Piyanut; Youngvises, Napaporn; Jakmunee, Jaroon

    2011-05-15

    Ceric ammonium nitrate has been used for qualitative analysis of ethanol. It forms an intensely colored unstable complex with alcohol. In this work, a simple flow injection (FI) colorimetric method was developed for the determination of ethanol, based on the reaction of ethanol with ceric ion in acidic medium to produce a red colored product having maximum absorption at 415 nm. Absorbance of this complex could be precisely measured in the FI system. A standard or sample solution was injected into a deionized water donor stream and flowed to a gas diffusion unit, where the ethanol diffused through a gas permeable membrane made of plumbing PTFE tape into an acceptor stream to react with ceric ammonium nitrate in nitric acid. Color intensity of the reddish product was monitored by a laboratory made LED based colorimeter and the signal was recorded on a computer as a peak. Peak height obtained was linearly proportional to the concentration of ethanol originally presented in the injected solution in the range of 0.1-10.0% (v/v) (r(2)=0.9993), with detection limit of 0.03% (v/v). With the use of gas diffusion membrane, most of the interferences could be eliminated. The proposed method was successfully applied for determination of ethanol in some alcoholic beverages, validating by gas chromatographic method.

  8. Flow injection analysis of nitrate and nitrite in commercial baby foods.

    Science.gov (United States)

    Chetty, Adrian A; Prasad, Surendra

    2016-04-15

    Commercial baby foods are an easy alternative to home-made meals especially for working parents in a nuclear family therefore it is imperative to determine the nitrate and nitrite content in commercially available baby foods varieties marketed in Fiji. A total of 108 baby food samples were analyzed for nitrate and nitrite using our standardized flow injection analysis (FIA) technique with colorimetric detection technique employing sulfanilamide and N-(1-naphthyl)ethylenediamine dihydrochloride as color reagents where the samples throughput was 38 h(-1). The commercial baby food varieties chosen comprised of vegetables, cereals, fruits and milk. The study shows that the nitrate content of the baby foods studied ranges from 2.10 to 220.67 mg kg(-1) whereas the nitrite content ranges from 0.44 to 3.67 mg kg(-1). Typical recoveries of spiked nitrate residues ranged from 92% to 106%. The study shows that the average nitrate content of commercially available baby foods in Fiji descends below the maximum level proposed by the European Union Legislation. Copyright © 2015 Elsevier Ltd. All rights reserved.

  9. Flow injection spectrophotometry using natural reagent from Morinda citrifolia root for determination of aluminium in tea.

    Science.gov (United States)

    Tontrong, Sopa; Khonyoung, Supada; Jakmunee, Jaroon

    2012-05-01

    A flow injection (FI) spectrophotometric method with using natural reagent extracted from Morinda citrifolia root has been developed for determination of aluminium. The extract contained anthraquinone compounds which could react with Al(3+) to form reddish complexes which had maximum absorption wavelength at 499.0nm. The extract could be used as a reagent in FI system without further purification to obtain pure compound. A sensitive method for determination of aluminium in concentration range of 0.1-1.0mgL(-1), with detection limit of 0.05mgL(-1) was achieved. Relative standard deviations of 1.2% and 1.7% were obtained for the determination of 0.1 and 0.6mgL(-1) Al(3+) (n=11). Sample throughput of 35h(-1) was achieved with the consumption of 3mL each of carrier and reagent solutions per injection. The developed method was successfully applied to tea samples, validated by the FAAS standard method. The method is simple, fast, economical and could be classified as a greener analytical method.

  10. Screening and determination of sulphonamide residues in bovine milk samples using a flow injection system.

    Science.gov (United States)

    Fernandes, Flávio Cesar Bedatty; Silva, Aline Santana; Rufino, José Luiz; Pezza, Helena Redigolo; Pezza, Leonardo

    2015-01-01

    A new, simple, rapid and sensitive flow injection spectrophotometric method was developed for the screening and determination of sulphonamides in bovine milk samples. The method is based on the condensation of sulphathiazole, sulphamethazine, and sulphadimethoxine with p-dimethylaminobenzaldehyde (p-DAB) in acid medium, in the presence of sodium dodecyl sulphate (SDS), producing a yellow compound (λmax=465 nm). Optimisation of the experimental parameters was performed using a multivariate methodology. The linear range was 90-500 μg/L and the limits of detection and quantification were in the ranges 25-29 μg/L and 84-88 μg/L, respectively. The procedure was applied for the determination of sulphonamide antibiotics in bovine milk samples submitted to a prior extraction procedure based on QuEChERS (Quick, Easy, Cheap, Effective, Rugged and Safe) methodology. Recoveries of 60.5-70.5% were achieved for milk samples spiked with 0.09, 0.1, 0.2, and 0.3 μg/g of each sulphonamide.

  11. Evaluation of Antibacterial Enrofloxacin in Eggs by Matrix Solid Phase Dispersion-Flow Injection Chemiluminescence

    Directory of Open Access Journals (Sweden)

    Xiaocui Duan

    2014-01-01

    Full Text Available The study based on the chemiluminescence (CL reaction of potassium ferricyanide and luminol in sodium hydroxide medium, enrofloxacin (ENRO could dramatically enhance CL intensities and incorporated with matrix solid-phase dispersion (MSPD technique (Florisil used as dispersant, dichloromethane eluted the target compounds. A simple flow injection chemiluminescence (FL-CL method with MSPD technique for determination of ENRO in eggs was described. Under optimal conditions, the CL intensities were linearly related to ENRO concentration ranging from 4.0×10-8 g.L−1 to 5.0×10-5 g.L−1, with a correlation coefficient of 0.9989 and detection limit of 5.0×10-9 g.L−1. The relative standard deviation was 3.6% at an ENRO concentration of 2.0×10-6 g.L−1. Our testing technique can help ensure food safety, and thus, protect public health.

  12. Determination of Melatonin in Rat Pineal Gland and Drug with Flow-Injection Chemiluminescence

    Institute of Scientific and Technical Information of China (English)

    WEI,Shou-Lian; ZHAO,LI-Xia; CHENG,Xiang-Lei; LIN,Jin-Ming

    2007-01-01

    A flow-injection chemiluminescence(CL)method for the determination of melatonin based on the CL reaction of melatonin with hydrogen peroxide and sodium hypochlorite(NaOCl)in a basic alkaline solution was developed.The possible CL mechanism has been discussed,and a proposal for the reaction pathway was given that singlet oxygen was clarified to be produced in this reaction system and was responsible for the CL emission.Under the optimized conditions.the linear concentration range of application was 1.0 X 10-7-2.5×10-4 mol·L-1 with a detection Iimit of 5.0X 10-8 mol·L-1(S/N=3).The relative standard deviation for eight repeated measurements of 1.0×10-6 mol·L-1 melatonin was 2.8%.The interferences of several important biological substances.some indole compound,cations and anions were studied.No interference was found for the anions,glucose,starch,most of cations and low concentration(less than 3.0×10-6 mol·L-1)of some biological substances and indole compound.The method was applied to the determination of melatonin in rat pineal gland and drug with satisfactory results.The sample throughput was 90 injections per hour.

  13. Flow injection analysis as a tool for enhancing oceanographic nutrient measurements--a review.

    Science.gov (United States)

    Worsfold, Paul J; Clough, Robert; Lohan, Maeve C; Monbet, Philippe; Ellis, Peter S; Quétel, Christophe R; Floor, Geerke H; McKelvie, Ian D

    2013-11-25

    Macronutrient elements (C, N and P) and micronutrient elements (Fe, Co, Cu, Zn and Mn) are widely measured in their various physico-chemical forms in open ocean, shelf sea, coastal and estuarine waters. These measurements help to elucidate the biogeochemical cycling of these elements in marine waters and highlight the ecological and socio-economic importance of the oceans. Due to the dynamic nature of marine waters in terms of chemical, biological and physical processes, it is advantageous to make these measurements in situ and in this regard flow injection analysis (FIA) provides a suitable shipboard platform. This review, therefore, discusses the role of FIA in the determination of macro- and micro-nutrient elements, with an emphasis on manifold design and detection strategies for the reliable shipboard determination of specific nutrient species. The application of various FIA manifolds to oceanographic nutrient determinations is discussed, with an emphasis on sensitivity, selectivity, high throughput analysis and suitability for underway analysis and depth profiles. Strategies for enhancing sensitivity and minimizing matrix effects, e.g. refractive index (schlieren) effects and the important role of uncertainty budgets in underpinning method validation and data quality are discussed in some detail.

  14. Ceramic Carbon/Polypyrrole Materials for the Construction of Bienzymatic Amperometric Biosensor for Glucose

    Institute of Scientific and Technical Information of China (English)

    2001-01-01

    A novel amperometric glucose biosensor was constructed by electrochemical formation of a polypyrrole (PPy) membrane in the presence of glucose oxidase (GOD) on the surface of a horseradish peroxidase (HRP) modified ferrocenecarboxylic acid (FCA) mediated sol-gel derived ceramic carbon electrode. The amperometric detection of glucose was carried out at +0.16 V (vs. SCE) in 0.1 mol/L phosphate buffer solution (pH 6.9) with a linear response range between 8.0×10-5 and 1.3×10-3 mol/L of glucose. The biosensor showed a good suppression of inter- ference and a negligible deviation in the amperometric detection.

  15. The Analysis of Saccharides in Chrysanthemi Flos by Capillary Electrophoresis-Amperometric Detection%菊花中糖类组分的毛细管电泳——安培检测研究

    Institute of Scientific and Technical Information of China (English)

    朱金坤; 姚孝林; 郑胜彪; 唐婧

    2012-01-01

    本文采用毛细管区带电泳-安培检测法(CZE-AD),研究了四类菊花中的常见单糖及蔗糖的分离、检测方法。在选定的实验条件下,可在20分钟内实现对葡萄糖、果糖、半乳糖、蔗糖的有效分离;待测糖类在铜电极上具有良好的电流响应、检测灵敏度(LOD:~1.0×10-6mol/L)及适宜的线性范围(5.0×10-6~5.0×10-4mol/L)。实验对滁菊、杭黄菊、贡菊、亳菊中的糖类组分进行了CZE-AD分离检测,方法具有良好的重现性及应用前景。检测结果表明,四类菊花中常见糖类组分的含量差异较大,可为相关植物资源的开发利用提供参考;检测方法简单、快速、有效,可用于菊花中常见糖类成分的测定及质量控制。%In this paper,the determination of normal saccharides in four kinds of Chrysanthemi Flos was investigated with capillary zone electrophoresis-amperometric detection method(CZE-AD).Under the optimized conditions,glucose,fructose,galactose and sucrose could be separated in 20 min.These analyzed saccharides gained excellent current response,detection limits(LOD): ~1.0×10-6mol/L and adequate linear ranges(5.0×10-6~5.0×10-4mol/L).The saccharides in four kinds of Chrysanthemi Flos(Chu-Ju,Hanghuang-Ju,Gong-Ju,Bo-Ju) were analyzed,and the results indicated good reproducibility and applicability of this proposed CZE-AD method.It could be found that the concerns of saccharides varied from one kind of Chrysanthemi Flos to another,and the detection data would provide reference to exploit the corresponding plant resources efficiently.This proposed detection method was simple,quick and effective with potential application in the analysis of saccharides for quality control of Chrysanthemi Flos.

  16. Development and validation of 2-deoxy-2-chloro-D-glucose impurity analysis in [{sup 18}F]FDG by three potential-time waveforms of high-performance liquid chromatography/pulsed amperometric detection

    Energy Technology Data Exchange (ETDEWEB)

    Farn, S.-S. [Isotope Application Division, Institute of Nuclear Energy Research, Taoyuan County, Taiwan (China)], E-mail: amanda@iner.gov.tw; Yeh, Y.-H.; Lin, W.-J.; Shen, L.-H. [Isotope Application Division, Institute of Nuclear Energy Research, Taoyuan County, Taiwan (China)

    2009-02-15

    A suitable three potential-time waveforms for the electrochemical detection of 2-deoxy-2-chloro-D-glucose (ClDG) by gold working electrode and palladium reference electrode have been developed and method validation was performed on Waters 2796 Bioalliance HPLC system coupled with pulsed amperometric detection (HPLC/PAD). FDG and ClDG could be completely separated by 50 mM NaOH mobile phase at a flow rate of 1.0 ml/min; 30 deg. C analytical column temperature; and E1 of 200 mV, T1 of 900 mS; E2 of -770 mV, T2 of 10 mS; E3 of 1400 mV, T3 of 10 mS; acquisition delay (AD) of 300 mS. The validation results were shown as follows: (1) in specificity study, mannose, FDG and ClDG could be completely separated and the retention times of these were 6.2, 11.1 and 13.5 min, respectively, with a total run time of 20 min; (2) the intraday repeatable precision expressed with the CV% in six successive analysis was 0.52% (for FDG) and 0.83% (for ClDG); (3) the interday variability precision expressed with the CV% value of the repeatable precision of 3 days was 0.99%, 0.52% and 0.58% for FDG and 0.71%, 0.83% and 1.24% for ClDG; both the CV% of intraday and interday reproducibilities of FDG and ClDG were better than 1.5%; (4) the accuracy and recovery of FDG and ClDG expressed with the percentage of mean value of three successive analysis were 99.75% (for FDG) and 100.68% (for ClDG) which were all greater than 95%; (5) under optimum conditions, the limit of detection of FDG and ClDG was 0.41 and 0.68 {mu}g/ml, and the limit of quantization of FDG and ClDG was 1.24 and 2.04 {mu}g/ml; (6) the correlation coefficient (r) value of linearity is over 0.999 by 5-50 {mu}g/ml ranges of both compounds, respectively; (7) no interference peak effects by composition of mobile phase or increasing/decreasing flow rate or change of temperature was observed.

  17. Determination of Monosaccharides and Disaccharides in Dairy Product by Ions Chromatography and Pulsed Amperometric Detection%离子色谱脉冲安培法测定乳制品中5种单双糖

    Institute of Scientific and Technical Information of China (English)

    杨晓敏

    2015-01-01

    提出了一种以离子色谱-脉冲安培检测法测定乳制品中5种单双糖(半乳糖、葡萄糖、果糖、蔗糖、乳糖)的方法。乳制品经前处理后采用CarboPac PA10色谱柱为分离柱,氢氧化钾为淋洗液,梯度洗脱,脉冲安培检测器( PAD)检测,以保留时间定性,外标法定量。结果表明,半乳糖、葡萄糖、果糖、蔗糖、乳糖在0.1~20.0 mg/kg浓度范围内呈良好的线性关系,回收率分别为:84.3%~91.0%、83.2%~93.5%、88.0%~93.3%、89.2%~98.0%、85.9%~96.9%,检出限分别为0.18、0.75、2.3、1.5、3.0 mg/kg,精密度分别为2.65%~4.55%、3.29%~5.01%、3.45%~4.10%、1.89%~3.62%、2.31%~4.57%。对市场上主要的几种乳制品进行检测,效果良好。%A chromatographic method was developed for the determination of monosaccharides and disaccharides (galactose, glucose, fructose, sucrose and lactose) in dairy product. CarboPac PA10 high performance anion exchange column ( HPAEC ) as splitter, KOH as eluent, gradient elution, pulsed amperometric detection ( PAD ) , qualitative analysis with retaining time, quantitative analysis with external reference method. The results showed that the linear relation of galactose, glucose, fructose, sucrose and lactose was well in the range of 0. 1~20. 0 mg/kg, the recoveries of these using PAD were 84. 3% ~91. 0%, 83. 2% ~93. 5%, 88. 0% ~93. 3%, 89. 2% ~98. 0%, 85. 9% ~96. 9%, the detection limits of these were 0. 18, 0. 75, 2. 3, 1. 5, 3. 0 mg/kg, the precision of these were 2. 65% ~4. 55%, 3. 29% ~5. 01%, 3. 45% ~4. 10%, 1. 89% ~3. 62%, 2. 31% ~4. 57%. The result about the detection of several main dairy product showed the effect was good.

  18. Fast spectrophotometric determination of fluoride in ground waters by flow injection using partial least-squares calibration

    Energy Technology Data Exchange (ETDEWEB)

    Arancibia, Juan A.; Rullo, Anabel; Olivieri, Alejandro C.; Di Nezio, Susana; Pistonesi, Marcelo; Lista, Adriana; Fernandez Band, Beatriz S

    2004-06-04

    The presence of sulphate constitutes a serious interference in the usual zirconium lake-based spectrophotometric method for the determination of fluoride in water. In this report, full spectral data have been recorded for the zirconium lake of 2-(parasulfophenylazo)-1,8-dihydroxy-3,6-naphthalene-disulfonate (SPADNS) in the simultaneous presence of fluoride and sulphate, as obtained with a flow injection system with a diode-array detector. The information has been processed with partial least-squares (PLS) multivariate calibration. Adequate modeling using a sixteen-sample calibration set allows fluoride to be determined in ground waters by the automated flow injection method, even in the presence of sulphate in concentrations up to 1000 mg l{sup -1}. In the calibration range 0-1.50 mg l{sup -1} for fluoride, the limit of detection is 0.1 mg l{sup -1}. The fluoride contents in real samples, as determined with the present method, were satisfactorily compared with those provided by ion selective potentiometry.

  19. Combination of Flow Injection and Electrothermal Atomic Absorption Spectrometry

    DEFF Research Database (Denmark)

    Hansen, Elo Harald; Nielsen, Steffen

    1999-01-01

    The paper discusses the advantages gained by exploiting this combination, FI-ETAAS. Emphasis is placed on illlustrating various avenues to perform on-line preconcentration of metal ions in order to obtain very low limits of detection of the measurand, and ways and means to enhance the selectivity...

  20. Development and characterization of a microfluidic glucose sensing system based on an enzymatic microreactor and chemiluminescence detection

    NARCIS (Netherlands)

    Moon, B. -U; de Vries, M. G.; Westerink, B. H. C.; Verpoorte, E.

    2012-01-01

    Chemiluminescence detection was developed as an alternative to amperometric detection for glucose analysis in a portable, microfluidics-based continuous glucose monitoring system. Amperometric detection allows easy determination of hydrogen peroxide, a product of the glucose oxidase-catalyzed reacti

  1. Development and characterization of a microfluidic glucose sensing system based on an enzymatic microreactor and chemiluminescence detection

    NARCIS (Netherlands)

    Moon, B. -U; de Vries, M. G.; Westerink, B. H. C.; Verpoorte, E.

    Chemiluminescence detection was developed as an alternative to amperometric detection for glucose analysis in a portable, microfluidics-based continuous glucose monitoring system. Amperometric detection allows easy determination of hydrogen peroxide, a product of the glucose oxidase-catalyzed

  2. Amperometric Bioelectronic Tongue for glucose determination

    Directory of Open Access Journals (Sweden)

    Yazan Al-Issa

    2015-03-01

    Full Text Available An amperometric Bioelectronic Tongue is reported for glucose determination that contains eight sensor electrodes constructed using different metal electrodes (Pt, Au, oxidoreductase enzymes (glucose oxidase, ascorbate oxidase, uricase, and membrane coatings (Nafion, chitosan. The response to varying concentrations of glucose, ascorbic acid, uric acid, and acetaminophen was tested for two models, concentration determination by current density measurements at individual electrodes and concentration determination by a linear regression model for the entire electrode array. The reduced chi-squared for the full array model was found to be about one order of magnitude lower than that for the individual-electrode model. Discrimination of glucose from chemical interference by the other three species is accomplished through a combination of enzyme catalysis, metal electrocatalysis, and membrane surface charge. The benefit of incorporating enzyme electrodes into the sensor array is illustrated by the lower correlation coefficients between different enzyme electrodes relative to non-enzyme coated electrodes. This approach can be more generally applied to detection of other substrates of oxidoreductase enzymes.

  3. Highly sensitive amperometric sensor for micromolar detection of trichloroacetic acid based on multiwalled carbon nanotubes and Fe(II)–phtalocyanine modified glassy carbon electrode

    Energy Technology Data Exchange (ETDEWEB)

    Kurd, Masoumeh [Department of Chemistry, University of Kurdistan, P. O. Box 416, Sanandaj (Iran, Islamic Republic of); Salimi, Abdollah, E-mail: absalimi@uok.ac.ir [Department of Chemistry, University of Kurdistan, P. O. Box 416, Sanandaj (Iran, Islamic Republic of); Research Center for Nanotechnology, University of Kurdistan, P. O. Box 416, Sanandaj (Iran, Islamic Republic of); Hallaj, Rahman [Department of Chemistry, University of Kurdistan, P. O. Box 416, Sanandaj (Iran, Islamic Republic of)

    2013-04-01

    A highly sensitive electrochemical sensor for the detection of trichloroacetic acid (TCA) is developed by subsequent immobilization of phthalocyanine (Pc) and Fe(II) onto multiwalled carbon nanotubes (MWCNTs) modified glassy carbon (GC) electrode. The GC/MWCNTs/Pc/Fe(II) electrode showed a pair of well-defined and nearly reversible redox couple correspondent to (Fe(III)Pc/Fe(II)Pc) with surface-confined characteristics. The surface coverage (Γ) and heterogeneous electron transfer rate constant (k{sub s}) of immobilized Fe(II)–Pc were calculated as 1.26 × 10{sup −10} mol cm{sup −2} and 28.13 s{sup −1}, respectively. Excellent electrocatalytic activity of the proposed GC/MWCNTs/Pc/Fe(II) system toward TCA reduction has been indicated and the three consequent irreversible peaks for electroreduction of CCl{sub 3}COOH to CH{sub 3}COOH have been clearly seen. The observed chronoamperometric currents are linearly increased with the concentration of TCA at concentration range up to 20 mM. Detection limit and sensitivity of the modified electrode were 2.0 μM and 0.10 μA μM{sup −1} cm{sup −2}, respectively. The applicability of the sensor for TCA detection in real samples was tested. The obtained results suggest that the proposed system can serve as a promising electrochemical platform for TCA detection. Highlights: ► Phthalocyanine (PC) and Fe(II) immobilized onto MWCNTs modified GC electrode. ► A pair of well-defined redox couple correspondent to (Fe(III)Pc/Fe(II)Pc) observed. ► Modified electrode shows excellent catalytic activity to electroreduction of CCl{sub 3}COOH. ► Amperometry and cyclic voltammetry techniques were used for detection of CCl{sub 3}COOH. ► Detection limit and sensitivity were 2.0 μM and 0.10 μA μM{sup −1} cm{sup −2}, respectively.

  4. A novel way for detection of antiparkinsonism drug entacapone via electrodeposition of silver nanoparticles/functionalized multi-walled carbon nanotubes as an amperometric sensor

    Energy Technology Data Exchange (ETDEWEB)

    Baghayeri, Mehdi, E-mail: m.baghayeri@hsu.ac.ir [Department of Chemistry, Faculty of Science, Hakim Sabzevari University, P.O. Box 397, Sabzevar (Iran, Islamic Republic of); Tehrani, Maliheh Barazandeh [Department of Medicinal Chemistry, Faculty of Pharmacy, Pharmaceutical Research Center, Tehran University of Medical Sciences, Tehran (Iran, Islamic Republic of); Amiri, Amirhassan; Maleki, Behrooz; Farhadi, Samaneh [Department of Chemistry, Faculty of Science, Hakim Sabzevari University, P.O. Box 397, Sabzevar (Iran, Islamic Republic of)

    2016-09-01

    Silver (Ag) nanoparticles were electrochemically deposited on the film of a metformin functionalized multi-walled carbon nanotube modified glassy carbon electrode (Met-MWCNT/GCE), which fabricated an Ag@Met-MWCNT nanocomposite sensor (Ag@Met-MWCNT/GCE) to detect entacapone (ENT). The Ag@Met-MWCNT nanocomposite was characterized by field emission scanning electrochemical microscopy (FESEM), X-ray diffraction (XRD) analysis, FT-IR and electrochemical tests. The modified electrode showed a large electrocatalytic activity for reduction of ENT. This improved activity indicates that Met@MWCNT plays a crucial role in the dispersion and stabilization of Ag nanoparticles on GCE. Under the optimized conditions the linear range for the detection of the ENT was obtained to be 0.05 to 70.0 μM with a low detection limit of 15.3 nM. The proposed sensor can effectively analyse ENT concentration in pharmaceutical formulations and human urine samples, avoiding interference, and is a promising ENT sensor due to good sensitivity, stability and low cost. - Graphical abstract: Schematic graph for fabrication and application of sensor. Display Omitted - Highlights: • Silver nanoparticles were electrochemically deposited on the modified glassy carbon electrode. • The modified electrode showed a large electrocatalytic activity for reduction of entacapone. • The proposed sensor can effectively analyse entacapone concentration in pharmaceutical formulations and human urine samples.

  5. A choline oxidase amperometric bioassay for the detection of mustard agents based on screen-printed electrodes modified with Prussian Blue nanoparticles.

    Science.gov (United States)

    Arduini, Fabiana; Scognamiglio, Viviana; Covaia, Corrado; Amine, Aziz; Moscone, Danila; Palleschi, Giuseppe

    2015-02-13

    In this work a novel bioassay for mustard agent detection was proposed. The bioassay is based on the capability of these compounds to inhibit the enzyme choline oxidase. The enzymatic activity, which is correlated to the mustard agents, was electrochemically monitored measuring the enzymatic product, hydrogen peroxide, by means of a screen-printed electrode modified with Prussian Blue nanoparticles. Prussian Blue nanoparticles are able to electrocatalyse the hydrogen peroxide concentration reduction at low applied potential (-50 mV vs. Ag/AgCl), thus allowing the detection of the mustard agents with no electrochemical interferences. The suitability of this novel bioassay was tested with the nitrogen mustard simulant bis(2-chloroethyl)amine and the sulfur mustard simulants 2-chloroethyl ethyl sulfide and 2-chloroethyl phenyl sulfide. The bioassay proposed in this work allowed the detection of mustard agent simulants with good sensitivity and fast response, which are excellent premises for the development of a miniaturised sensor well suited for an alarm system in case of terrorist attacks.

  6. Flame AAS determination of lead in water with flow-injection preconcentration and speciation using functionalized cellulose sorbent.

    Science.gov (United States)

    Naghmush, A M; Pyrzyńska, K; Trojanowicz, M

    1995-06-01

    The on-line solid phase extraction of trace amount of lead in flow-injection system with flame AAS detection was investigated using cellulose sorbents with phosphonic acid and carboxymethyl groups, C(18) sorbent non-modified and modified with Pyrocatechol Violet or 8-quinolinol, commercial chelating sorbents Chelex 100 and Spheron Oxin 1000, non-polar sorbent Amberlite XAD-2 modified with Pyrocatechol Violet and several cation-exchange resins. The best dynamic characteristics of retention were observed for functionalized cellulose sorbents. For Cellex P assumed as optimum sorbent, elution with a separate fractions of nitric acid and ethanol allows the differentiation between tetraalkyllead and sum of inorganic lead and organolead species of smaller number of alkyl groups. The detection limit for the determination of inorganic Pb(II) was estimated as 0.17 microg/l. at preconcentration from 50 ml sample at a flow rate of 7 ml/min.

  7. Amperometric Biosensors for Real Time Assays of Organophosphates

    Directory of Open Access Journals (Sweden)

    Kamil Kuca

    2008-09-01

    Full Text Available An amperometric biosensor based on acetylcholinesterase (AChE immobilized in gelatin was used to develop an assay for the organophosphate paraoxon. The more traditional manner employing preincubation was used for comparison between measurement procedures, although the aim of the study was to examine the performance of the biosensor for real time monitoring of organophosphates. The biosensor was immersed in a reaction chamber and paraoxon was injected inside. We were able to detect 200 pg of paraoxon within one minute or 2.5 ppb when the biosensor was preincubed in the sample solution for 15 minutes. The practical impact and expectations are discussed.

  8. Flow injection-chemical vapor generation atomic fluorescence spectrometry hyphenated system for organic mercury determination: A step forward

    Energy Technology Data Exchange (ETDEWEB)

    Angeli, Valeria [National Research Council of Italy, C.N.R., Istituto di Chimica dei Composti Organo Metallici - ICCOM-UOS Pisa, Area di Ricerca, Via G. Moruzzi 1, 56124 Pisa (Italy); Biagi, Simona [National Research Council of Italy, C.N.R., Istituto per i Processi Chimico-Fisici - IPCF-UOS Pisa, Area di Ricerca, Via G. Moruzzi 1, 56124 Pisa (Italy); Ghimenti, Silvia [University of Pisa, Department of Chemistry and Industrial Chemistry, Via Risorgimento 35, 56126 Pisa (Italy); Onor, Massimo; D' Ulivo, Alessandro [National Research Council of Italy, C.N.R., Istituto di Chimica dei Composti Organo Metallici - ICCOM-UOS Pisa, Area di Ricerca, Via G. Moruzzi 1, 56124 Pisa (Italy); Bramanti, Emilia, E-mail: bramanti@pi.iccom.cnr.it [National Research Council of Italy, C.N.R., Istituto di Chimica dei Composti Organo Metallici - ICCOM-UOS Pisa, Area di Ricerca, Via G. Moruzzi 1, 56124 Pisa (Italy)

    2011-11-15

    Monomethylmercury and ethylmercury were determined on line using flow injection-chemical vapor generation atomic fluorescence spectrometry without neither requiring a pre-treatment with chemical oxidants, nor UV/MW additional post column interface, nor organic solvents, nor complexing agents, such as cysteine. Inorganic mercury, monomethylmercury and ethylmercury were detected by atomic fluorescence spectrometry in an Ar/H{sub 2} miniaturized flame after sodium borohydride reduction to Hg{sup 0}, monomethylmercury hydride and ethylmercury hydride, respectively. The effect of mercury complexing agent such as cysteine, ethylendiaminotetracetic acid and HCl with respect to water and Ar/H{sub 2} microflame was investigated. The behavior of inorganic mercury, monomethylmercury and ethylmercury and their cysteine-complexes was also studied by continuous flow-chemical vapor generation atomic fluorescence spectrometry in order to characterize the reduction reaction with tetrahydroborate. When complexed with cysteine, inorganic mercury, monomethylmercury and ethylmercury cannot be separately quantified varying tetrahydroborate concentration due to a lack of selectivity, and their speciation requires a pre-separation stage (e.g. a chromatographic separation). If not complexed with cysteine, monomethylmercury and ethylmercury cannot be separated, as well, but their sum can be quantified separately with respect to inorganic mercury choosing a suitable concentration of tetrahydroborate (e.g. 10{sup -5} mol L{sup -1}), thus allowing the organic/inorganic mercury speciation. The detection limits of the flow injection-chemical vapor generation atomic fluorescence spectrometry method were about 45 nmol L{sup -1} (as mercury) for all the species considered, a relative standard deviation ranging between 1.8 and 2.9% and a linear dynamic range between 0.1 and 5 {mu}mol L{sup -1} were obtained. Recoveries of monomethylmercury and ethylmercury with respect to inorganic mercury were

  9. Assembly of graphene and nickel nanoparticles on anion exchange resin microspheres for the amperometric detection of carbohydrates in combination with capillary electrophoresis.

    Science.gov (United States)

    Zhang, Ren; Lu, Sijie; Zhang, Luyan; Chen, Gang

    2014-12-29

    Graphene and nickel nanoparticles (NiNPs) were assembled on anion exchange resin (AER) microspheres based on the electrostatic interaction between graphene oxide sheets and AER and the subsequent chemical reduction. The prepared AER@graphene-NiNP composite core-shell microspheres were characterized by scanning electron microscopy, energy dispersive spectroscopy, X-ray diffraction, and Fourier transform infrared spectroscopy. Moreover, they were embedded in the bores of pipette tips to fabricate electrodes. The performance of the novel electrodes was demonstrated by measuring sucrose, glucose and fructose in combination with capillary electrophoresis. The three analytes were well separated within 8min in a 40cm long capillary at a separation voltage of 12kV. The graphene-NiNP composite microsphere electrodes exhibited higher sensitivity (213.578-317.064nAmM(-1)), lower detection limits (0.75-1.05μM) and enhanced separation efficiency in the detection of these carbohydrates. The advantages of the electrodes include ease of fabrication, low cost and pronounced electrocatalytic activity toward carbohydrates, indicating great promise for a wide range of applications.

  10. Ultrasensitive amperometric immunosensor for PSA detection based on Cu2O@CeO2-Au nanocomposites as integrated triple signal amplification strategy.

    Science.gov (United States)

    Li, Faying; Li, Yueyun; Feng, Jinhui; Dong, Yunhui; Wang, Ping; Chen, Lei; Chen, Zhiwei; Liu, Hui; Wei, Qin

    2017-01-15

    In this work, a novel label-free electrochemical immunosensor was developed for the quantitative detection of prostate specific antigen (PSA). To this end, the amino functionalized cuprous oxide @ ceric dioxide (Cu2O@CeO2-NH2) core-shell nanocomposites were prepared to bond gold nanoparticles (Au NPs) by constructing stable Au-N bond between Au NPs and -NH2. Because the synergetic effect presents in Cu2O@CeO2 core-shell loaded with Au NPs (Cu2O@CeO2-Au), it shows better electrocatalytic activity towards the reduction of hydrogen peroxide (H2O2) than single Cu2O, Au NPs and Cu2O@CeO2. Featured by large specific surface area, good biocompatibility and good electrochemical properties which can greatly improve the electronic transmission rate, Cu2O@CeO2-Au was used as transducing materials to achieve efficiently capture antibodies and triple signal amplification of the proposed immunosensor. Under the optimal conditions, the proposed immunosensor exhibited a wide linear range from 0.1pg/mL to 100ng/mL with a low detection limit of 0.03pg/mL (S/N=3). Furthermore, the proposed label-free immunosensor has been used to determine PSA in human serum with satisfactory results. Meanwhile, it displayed good reproducibility, acceptable selectivity, and long-term stability, which had promising application in bioassay analysis.

  11. Fast fluorometric flow injection analysis of formaldehyde in atmospheric water

    Energy Technology Data Exchange (ETDEWEB)

    Dong, S.; Dasgupta, P.K.

    1987-06-01

    Formaldehyde can be determined in aqueous solution at a rate of 45 samples/h with a small sample requirement (100 ..mu..L). The fluorescence of 3,5-diacetyl-1,4-dihydrolutidine formed upon reaction of formaldehyde with ammonium acetate and 2,4-pentanedione (25 s, 95 /sup 0/C) is monitored with a filter fluorometer. The detection limit is 0.1 ..mu..M (3 ..mu..g/L) or 10 pmol of HCHO. The response is linear up to 3.3 ..mu..M (100 ..mu..g/L), the departure from linearity at 0.33 mM is 21%, but high levels are satisfactorily determined with a second-order calibration equation. Interference from S(IV) has been investigated in detail and completely eliminated by addition of H/sub 2/O/sub 2/ before rendering the sample alkaline. There are no effects from commonly occurring metal ions and anions; the method is very selective to formaldehyde compared to other carbonyl compounds. A S(IV)-containing preservative has been formulated for the stabilization of low concentrations of HCHO. Results are presented for fogwater samples. 8 figures, 41 references.

  12. 离子色谱-脉冲安培法检测酸奶中大豆低聚糖%Determination of Soybean Oligosaccharide in Yogurt by Ion Chromatography-pulsed Amperometric Detection

    Institute of Scientific and Technical Information of China (English)

    黄秋研; 郦明浩; 赵丹霞

    2015-01-01

    建立离子色谱-脉冲安培法检测酸奶中大豆低聚糖的方法。酸奶经处理后其大豆低聚糖含量(包括蔗糖、棉子糖、水苏糖3种成分)以CarboPac PA1高效阴离子交换柱为分析柱,醋酸钠为淋洗液,等度洗脱,脉冲安培检测器(PAD)检测,以保留时间定性,外标法定量。结果表明蔗糖、棉子糖、水苏糖在CarboPac PA1上可以在20 min内完成分离,且均具有较宽的线性范围。蔗糖、棉子糖、水苏糖平均回收率分别为98.67%,100.9%,98.91%,精密度测试结果的RSD分别为0.22%,0.41%,0.34%。该方法检测样品前处理操作简单,分离效果好,保留时间短,可作为酸奶中大豆低聚糖含量的一种快速检测方法。%An ion chromatography-pulsed amperometric detection method was developed for the determination of soybean oligosaccharide in Yogurt. The sucrose,raffinose and stachyose in soybean oligosaccharide were separated on a CarboPac PA1 high performance anion-exchange column by PAD and eluted in the isocratic elution mode with sodium acetate solution. The soybean oligosaccharide contents were finally qualitatived by retention time and quantitatived by external standard method. The results showed that sucrose ,raffinose and stachyose can be completely separated in 20 minutes on the CarboPac PA1 column with a wide range of linears. The average spike recoveries of sucrose,raffinose ,stachyose were 98.67%,100.9%,98.91%respectively and the RSD were 0.22 %,0.41 % and 0.34 %respectively. This method demonstrated to be simple with good seperation effects and short retention time,and thus had a promising potential for reapid determination of soybean oligosaccharide in Yogurt.

  13. Determination of total iodine in serum and urine samples by ion chromatography with pulsed amperometric detection - studies on analyte loss, optimization of sample preparation procedures, and validation of analytical method.

    Science.gov (United States)

    Błażewicz, Anna; Klatka, Maria; Dolliver, Wojciech; Kocjan, Ryszard

    2014-07-01

    A fast, accurate and precise ion chromatography method with pulsed amperometric detection was applied to evaluate a variety of parameters affecting the determination of total iodine in serum and urine of 81 subjects, including 56 obese and 25 healthy Polish children. The sample pretreatment methods were carried out in a closed system and with the assistance of microwaves. Both alkaline and acidic digestion procedures were developed and optimized to find the simplest combination of reagents and the appropriate parameters for digestion that would allow for the fastest, least time consuming and most cost-effective way of analysis. A good correlation between the certified and the measured concentrations was achieved. The best recoveries (96.8% for urine and 98.8% for serum samples) were achieved using 1ml of 25% tetramethylammonium hydroxide solution within 6min for 0.1ml of serum/urine samples. Using 0.5ml of 65% nitric acid solution the best recovery (95.3%) was obtained when 7min of effective digestion time was used. Freeze-thaw stability and long-term stability were checked. After 24 weeks 14.7% loss of iodine in urine, and 10.9% in serum samples occurred. For urine samples, better correlation (R(2)=0.9891) of various sample preparation procedures (alkaline digestion and application of OnGuard RP cartidges) was obtained. Significantly lower iodide content was found in samples taken from obese children. Serum iodine content in obese children was markedly variable in comparison with the healthy group, whereas the difference was less evident when urine samples were analyzed. The mean content in serum was 59.12±8.86μg/L, and in urine 98.26±25.93 for obese children when samples were prepared by the use of optimized alkaline digestion reinforced by microwaves. In healthy children the mean content in serum was 82.58±6.01μg/L, and in urine 145.76±31.44μg/L.

  14. Determination of gallic acid with rhodanine by reverse flow injection analysis using simplex optimization.

    Science.gov (United States)

    Phakthong, Wilaiwan; Liawruangrath, Boonsom; Liawruangrath, Saisunee

    2014-12-01

    A reversed flow injection (rFI) system was designed and constructed for gallic acid determination. Gallic acid was determined based on the formation of chromogen between gallic acid and rhodanine, resulting in a colored product with a λmax at 520 nm. The optimum conditions for determining gallic acid were also investigated. Optimizations of the experimental conditions were carried out based on the so-call univariate method. The conditions obtained were 0.6% (w/v) rhodanine, 70% (v/v) ethanol, 0.9 mol L(-1) NaOH, 2.0 mL min(-1) flow rate, 75 μL injection loop and 600 cm mixing tubing length, respectively. Comparative optimizations of the experimental conditions were also carried out by multivariate or simplex optimization method. The conditions obtained were 1.2% (w/v) rhodanine, 70% (v/v) ethanol, 1.2 mol L(-1) NaOH, flow rate 2.5 mL min(-1), 75 μL injection loop and 600 cm mixing tubing length, respectively. It was found that the optimum conditions obtained by the former optimization method were mostly similar to those obtained by the latter method. The linear relationship between peak height and the concentration of gallic acid was obtained over the range of 0.1-35.0 mg L(-1) with the detection limit 0.081 mg L(-1). The relative standard deviations were found to be in the ranges 0.46-1.96% for 1, 10, 30 mg L(-1) of gallic acid (n=11). The method has the advantages of simplicity extremely high selectivity and high precision. The proposed method was successfully applied to the determination of gallic acid in longan samples without interferent effects from other common phenolic compounds that might be present in the longan samples collected in northern Thailand.

  15. Emerging flow injection mass spectrometry methods for high-throughput quantitative analysis.

    Science.gov (United States)

    Nanita, Sergio C; Kaldon, Laura G

    2016-01-01

    Where does flow injection analysis mass spectrometry (FIA-MS) stand relative to ambient mass spectrometry (MS) and chromatography-MS? Improvements in FIA-MS methods have resulted in fast-expanding uses of this technique. Key advantages of FIA-MS over chromatography-MS are fast analysis (typical run time quantitative screening of chemicals needs to be performed rapidly and reliably. The FIA-MS methods discussed herein have demonstrated quantitation of diverse analytes, including pharmaceuticals, pesticides, environmental contaminants, and endogenous compounds, at levels ranging from parts-per-billion (ppb) to parts-per-million (ppm) in very complex matrices (such as blood, urine, and a variety of foods of plant and animal origin), allowing successful applications of the technique in clinical diagnostics, metabolomics, environmental sciences, toxicology, and detection of adulterated/counterfeited goods. The recent boom in applications of FIA-MS for high-throughput quantitative analysis has been driven in part by (1) the continuous improvements in sensitivity and selectivity of MS instrumentation, (2) the introduction of novel sample preparation procedures compatible with standalone mass spectrometric analysis such as salting out assisted liquid-liquid extraction (SALLE) with volatile solutes and NH4(+) QuEChERS, and (3) the need to improve efficiency of laboratories to satisfy increasing analytical demand while lowering operational cost. The advantages and drawbacks of quantitative analysis by FIA-MS are discussed in comparison to chromatography-MS and ambient MS (e.g., DESI, LAESI, DART). Generally, FIA-MS sits 'in the middle' between ambient MS and chromatography-MS, offering a balance between analytical capability and sample analysis throughput suitable for broad applications in life sciences, agricultural chemistry, consumer safety, and beyond.

  16. Pharmacokinetic of pseudoephedrine in rat serum with luminol-pepsin chemiluminescence system by flow injection analysis.

    Science.gov (United States)

    Luo, Kai; Li, Yajuan; Zheng, Xiaohui; Song, Zhenghua

    2015-02-01

    Pepsin (Pep) accelerated the electron transferring rate of excited 3-aminophathlate and enhanced luminol-dissolved oxygen chemiluminescence (CL) intensity, and the flow injection (FI) luminol-Pep CL system was first developed. It was found that the CL intensity of luminol-Pep reaction could be remarkably inhibited by pseudoephedrine (PE); the decrement of CL intensity was linear to the logarithm of PE concentration in the range of 0.1∼100.0 nmol L(-1) with a detection limit of 0.03 nmol mL(-1) (3σ). At a flow rate of 2.0 mL min(-1), the complete process including washing and sampling was performed within 40 s, offering a sample throughput of 90 h(-1). This proposed method was successfully applied to determining PE in rat serum for 18 h after intragastric administration with the elimination ratio of 42.34 % and recoveries from 90.3 to 110.6 %. The pharmacokinetic results showed that PE could be rapidly absorbed into serum with peak concentration (C max) of 1.45 ± 0.18 g L(-1) at the time (T max) of 1.49 ± 0.02 h; the absorption half-life (0.35 ± 0.04 h), elimination half-life (1.86 ± 0.24 h), the area under curve (109.81 ± 6.03 mg L(-1) h(-1)), mean residence time (3.82 ± 0.27 h), and elimination rate constant (2.26 ± 0.23 L g(-1) h(-1)) in rats vivo were derived, respectively. The possible CL mechanism of luminol-Pep-PE reaction was discussed by FI-CL, fluorescence, and molecular docking (MD) methods.

  17. Amperometric detection of hydrogen peroxide at nano-nickel oxide/thionine and celestine blue nanocomposite-modified glassy carbon electrodes

    Energy Technology Data Exchange (ETDEWEB)

    Noorbakhsh, Abdollah [Department of Chemistry, University of Kurdistan, P.O. Box 416, Sanandaj (Iran, Islamic Republic of); Salimi, Abdollah [Department of Chemistry, University of Kurdistan, P.O. Box 416, Sanandaj (Iran, Islamic Republic of); Research Center for Nanotechnology, University of Kurdistan, P.O. Box 426, Sanandaj (Iran, Islamic Republic of)], E-mail: absalimi@uok.ac.ir

    2009-11-01

    A simple procedure was developed to prepare a glassy carbon (GC) electrode modified with nickel oxide (NiOx) nanoparticles and water-soluble dyes. By immersing the GC/NiOx modified electrode into thionine (TH) or celestine blue (CB) solutions for a short period of time (5-120 s), a thin film of the proposed molecules was immobilized onto the electrode surface. The modified electrodes showed stable and a well-defined redox couples at a wide pH range (2-12), with surface confined characteristics. In comparison to usual methods for the immobilization of dye molecules, such as electropolymerization or adsorption on the surface of preanodized electrodes, the electrochemical reversibility and stability of these modified electrodes have been improved. The surface coverage and heterogeneous electron transfer rate constants (k{sub s}) of thionin and celestin blue immobilized on a NiOx-GC electrode were approximately 3.5 x 10{sup -10} mol cm{sup -2}, 6.12 s{sup -1}, 5.9 x 10{sup -10} mol cm{sup -2} and 6.58 s{sup -1}, respectively. The results clearly show the high loading ability of the NiOx nanoparticles and great facilitation of the electron transfer between the immobilized TH, CB and NiOx nanoparticles. The modified electrodes show excellent electrocatalytic activity toward hydrogen peroxide reduction at a reduced overpotential. The catalytic rate constants for hydrogen peroxide reduction at GC/NiOx/CB and GC/NiOx/TH were 7.96 ({+-}0.2) x 10{sup 3} M{sup -1} s{sup -1} and 5.5 ({+-}0.2) x 10{sup 3} M{sup -1} s{sup -1}, respectively. The detection limit, sensitivity and linear concentration range for hydrogen peroxide detection were 1.67 {mu}M, 4.14 nA {mu}M{sup -1} nA {mu}M{sup -1} and 5 {mu}M to 20 mM, and 0.36 {mu}M, 7.62 nA {mu}M{sup -1}, and 1 {mu}M to 10 mM for the GC/NiOx/TH and GC/NiOx/CB modified electrodes, respectively. Compared to other modified electrodes, these modified electrodes have many advantages, such as remarkable catalytic activity, good

  18. Flow-injection analysis with multidetection as a useful technique for metal speciation.

    Science.gov (United States)

    Ruz, J; Rios, A; de Castro, M D; Valcarcel, M

    1986-03-01

    The analytical potential of a closed flow-injection system with multidetection by a single detector (for calculation of rate constants, reaction rate, dilution and amplification methods, etc.) is extended to simultaneous determinations for chromium speciation, with injection of the reagent(s) into the sample solution (which acts as the carrier).

  19. Continuous, pulsed and stopped flow in a u-flow injection system (numerical vs experimental)

    NARCIS (Netherlands)

    van Akker, E.B.; Bos, M.; van der Linden, W.E.

    1999-01-01

    The effects of continuous, pulsed and stopped flow on the dispersion of a sample injected into a μ-flow injection system were studied. A channel with a volume of 1 μl was used to compare experimental results with numerical results. The injection was 0.067 μl of bromocresolgreen solution into a borax

  20. Flow injection chemiluminescence determination of loxoprofen and naproxen with the acidic permanganate-sulfite system

    Institute of Scientific and Technical Information of China (English)

    Li-Juan Wang; Yu-Hai Tang; Yang-Hao Liu

    2011-01-01

    A novel flow injection chemiluminescence(CL)method for the determination of loxoprofen and naproxen was proposed based on the CL system of KMnO4 and Na2SO3 in acid media.The CL intensity of KMnO4-Na2SO3 was greatly enhanced in the presence of loxoprofen a

  1. Continuous, pulsed and stopped flow in a μ-flow injection system (numerical vs experimental)

    NARCIS (Netherlands)

    Akker, van E.B.; Bos, M.; Linden, van der W.E.

    1999-01-01

    The effects of continuous, pulsed and stopped flow on the dispersion of a sample injected into a μ-flow injection system were studied. A channel with a volume of 1 μl was used to compare experimental results with numerical results. The injection was 0.067 μl of bromocresolgreen solution into a borax

  2. Flow injection-chemical vapor generation atomic fluorescence spectrometry hyphenated system for organic mercury determination: A step forward

    Science.gov (United States)

    Angeli, Valeria; Biagi, Simona; Ghimenti, Silvia; Onor, Massimo; D'Ulivo, Alessandro; Bramanti, Emilia

    2011-11-01

    Monomethylmercury and ethylmercury were determined on line using flow injection-chemical vapor generation atomic fluorescence spectrometry without neither requiring a pre-treatment with chemical oxidants, nor UV/MW additional post column interface, nor organic solvents, nor complexing agents, such as cysteine. Inorganic mercury, monomethylmercury and ethylmercury were detected by atomic fluorescence spectrometry in an Ar/H 2 miniaturized flame after sodium borohydride reduction to Hg 0, monomethylmercury hydride and ethylmercury hydride, respectively. The effect of mercury complexing agent such as cysteine, ethylendiaminotetracetic acid and HCl with respect to water and Ar/H 2 microflame was investigated. The behavior of inorganic mercury, monomethylmercury and ethylmercury and their cysteine-complexes was also studied by continuous flow-chemical vapor generation atomic fluorescence spectrometry in order to characterize the reduction reaction with tetrahydroborate. When complexed with cysteine, inorganic mercury, monomethylmercury and ethylmercury cannot be separately quantified varying tetrahydroborate concentration due to a lack of selectivity, and their speciation requires a pre-separation stage (e.g. a chromatographic separation). If not complexed with cysteine, monomethylmercury and ethylmercury cannot be separated, as well, but their sum can be quantified separately with respect to inorganic mercury choosing a suitable concentration of tetrahydroborate (e.g. 10 - 5 mol L - 1 ), thus allowing the organic/inorganic mercury speciation. The detection limits of the flow injection-chemical vapor generation atomic fluorescence spectrometry method were about 45 nmol L - 1 (as mercury) for all the species considered, a relative standard deviation ranging between 1.8 and 2.9% and a linear dynamic range between 0.1 and 5 μmol L - 1 were obtained. Recoveries of monomethylmercury and ethylmercury with respect to inorganic mercury were never less than 91%. Flow injection

  3. Determination of Myo-Inositol in Infant, Pediatric, and Adult Formulas by Liquid Chromatography-Pulsed Amperometric Detection with Column Switching: Collaborative Study, Final Action 2011.18.

    Science.gov (United States)

    Butler-Thompson, Linda D; Jacobs, Wesley A; Schimpf, Karen J

    2015-01-01

    AOAC First Action Method 2011.18, Myo-Inositol (Free and Bound as Phosphatidylinositol) in Infant and Pediatric Formulas and Adult Nutritionals, was collaboratively studied. With this method free myo-inositol and phosphatidylinositol bound myo-inositol are extracted using two different sample preparation procedures, separated by ion chromatography using a combination of Dionex Carbo Pac PA1 and MA1 columns with column switching, and detected with pulsed amperometry using a gold electrode. Free myo-inositol is extracted from samples with dilute hydrochloric acid and water. Phosphatidylinositol is extracted from samples with chloroform and separated from other fats with silica SPE cartridges. Myo-inositol is then released from the glycerol backbone with concentrated acetic and hydrochloric acids at 120°C. During this collaborative study, nine laboratories from five different countries analyzed blind duplicates of nine infant and pediatric nutritional formulas for both free and phosphatidylinositol bound myo-inositol, and one additional laboratory only completed the free myo-inositol analyses. The method demonstrated acceptable repeatability and reproducibility and met the AOAC Stakeholder Panel on Infant Formula and Adult Nutritionals (SPIFAN) Standard Method Performance Requirements (SMPRs®) for free myo-inositol plus phosphatidylinositol bound myo-inositol for all the matrixes analyzed. SMPRs for repeatability were ≤5% RSD at myo-inositol concentrations of 2-68 mg/100 g ready-to-feed (RTF) liquid. SMPRs for reproducibility were ≤8% RSD in products with myo-inositol concentrations ranging from 2 to 68 mg/100 g RTF liquid. During this collaborative study, repeatability RSDs ranged from 0.51 to 3.22%, and RSDs ranged from 2.66 to 7.55% for free myo-inositol plus phosphatidylinositol bound myo-inositol.

  4. Modeling of Amperometric Immunosensor for CMOS Integration

    Institute of Scientific and Technical Information of China (English)

    Ce Li; Haigang Yang; Shanhong Xia; Chao Bian

    2006-01-01

    A circuit model of the Amperometric immunosensor for use in the biosensor system-on-chip simulation is proposed in this paper. The model parameters are extracted with several methods and verified by MATLAB and SPICE simulation. A CMOS potentiostat circuit required for conditioning the Amperometric immunosensor is also included in the circuit model. The mean square error norm of the simulated curve against the measured one is 8.65 × 10-17. The whole circuit has been fabricated in a 0.35am CMOS process.

  5. Kinetic flow-injection-spectrofluorimetric determination of aluminium(III) using Eriochrome Red B, sensitized by traces of fluoride

    Energy Technology Data Exchange (ETDEWEB)

    Carrillo, F. [Universidad Complutense de Madrid (Spain). Dept. de Quimica Analitica; Perez-Conde, C. [Universidad Complutense de Madrid (Spain). Dept. de Quimica Analitica; Camara, C. [Universidad Complutense de Madrid (Spain). Dept. de Quimica Analitica

    1996-01-01

    A flow injection-spectrofluorimetric method is reported for the determination of Al(III) based on the use of Eriochrome Red B and hexamethylenetetramine buffer, sensitized by the presence of fluoride at 80 C. Various chemical and physical variables affecting the reaction in the flow system were evaluated. The method is very sensitive with a detection limit of 0.1 {mu}g 1{sup -1} and a precision at the 5 {mu}g 1{sup -1} level of 2.6%. The calibration range is linear up to 1000 {mu}g 1{sup -1}. The method has been successfully applied to the determination of Al (III) in tap and mineral waters and urine samples. (orig.)

  6. Determination of zinc in edible oils by flow injection FAAS after extraction induced by emulsion breaking procedure.

    Science.gov (United States)

    Bakircioglu, Dilek; Topraksever, Nukte; Kurtulus, Yasemin Bakircioglu

    2014-05-15

    A new procedure using extraction induced by emulsion breaking (EIEB) procedure has been developed for extraction/preconcentration of zinc in various edible oils (canola oil, corn oil, hazelnut oil, olive oil, and sunflower oil) prior to its determination by the single line flow injection (FI) flame atomic absorption spectrometry (FAAS). Several parameters affecting the extraction efficiency of the procedure were investigated including the type and concentrations of surfactant, the concentration of HNO3, and the other operational conditions (emulsion breaking time and temperature). The limits of detection of 1.1 and 1.0 μg L(-1) were observed for zinc when aqueous standard and oil-based standards were added to the emulsions for calibration, respectively. The proposed procedure of combining EIEB and single line FI-FAAS can be regarded as a new procedure for the determination of zinc in edible oil samples.

  7. Method for the simultaneous determination of total polyphenol and anthocyan indexes in red wines using a flow injection approach.

    Science.gov (United States)

    González-Rodríguez, J; Pérez-Juan, P; Luque de Castro, M D

    2002-01-04

    A simultaneous and fast method for the determination of total polyphenol index (t.p.i.) and total anthocyan index (t.a.i.) has been developed by a flow injection approach and a diode array spectrophotometer for monitoring at 280 and 520 nm, respectively. Linear ranges were obtained from 20 to 70 index units and from 20 to 500 mg l(-1) for the t.p.i. and t.a.i., respectively. The results provided by the proposed method agree with those obtained using the polyphenol index at 280 nm and the Ribereau-Gayon method for the determination of total anthocyans. The sample throughout was 25-30 samples per hour. Analytical features such as repeatability, reproducibility and detection and quantification limits as well as the results of a robustness study based on the Steiner-Younden procedure are also given.

  8. Determination of mercury in estuarine sediments by flow injection-cold vapour atomic absorption spectrometry after microwave extraction

    Energy Technology Data Exchange (ETDEWEB)

    Martinez-Garcia, M.L.; Carlosena, A.; Lopez-Mahia, P.; Muniategui, S.; Prada, D. [University of La Coruna (Spain). Dept. Analytical Chemistry

    1999-01-01

    A flow injection-cold vapour atomic absorption spectrometric (CVAAS) method was developed for the determination of mercury at trace level in estuarine sediments using sodium tetra-hydro-borate (III) as reductant. The mercury was solubilized with nitric acid in closed vessels nd microwave oven heating. Instrumental and operational conditions (volume and concentration of reagents, reaction time, etc.) were optimized. The effect of several ions on the analytical signal was also studied; no interferences were recorded excepting for copper and nickel which caused a serious depressing effect. The detection limit obtained was 0.01 {mu}g g{sup -1}. The validation of the method was performed analyzing a certified reference sediment, BCR CRM 277 Estuarine Sediment. Good recovery (c.a. 98 %) and precision (< 3 %, RSD) were achieved. The proposed method was successfully applied to the determination of mercury in sediment samples from Ares-Betanzos Estuary (Galicia, NW Spain). (authors) 19 refs.

  9. Measuring the concentrations of drinking water disinfection by-products using capillary membrane sampling-flow injection analysis.

    Science.gov (United States)

    Geme, Gija; Brown, Michael A; Simone, Paul; Emmert, Gary L

    2005-10-01

    A capillary membrane sampling-flow injection analysis method is presented for selectively measuring the concentrations of total trihalomethanes (THMs) and total haloacetic acids (HAAs) in drinking water. The method is based on the reaction between nicotinamide and THM or HAA species to yield a fluorescent product. Two configurations are presented, one selective for total THMs and another selective for total HAAs. The construction of a capillary membrane sampler is described, and the results of method detection limit, accuracy and precision studies are reported for each method. Interference, selectivity and linearity studies are reported as well as the effect of temperature and ionic strength changes. Drinking water samples were analyzed by each proposed method and the results were compared to USEPA methods 502.2 and 552.3.

  10. Determination of Trace Amounts of Chromium(III) in Water Samples Using Online Flow Injection Catalytic Spectrophotometry

    Science.gov (United States)

    Zhao, Z. X.; Zhang, X. S.

    2017-01-01

    A new online flow injection spectrophotometric method for the determination of trivalent chromium was developed. This method is based on the property of trivalent chromium to be a catalyst for the oxidation of Indigo Carmine (IC) with potassium periodate and to lose its color in the presence of ethylenediaminetetraacetic acid and sodium tripolyphosphate. It was shown that Tween-20 serves as an additional accelerator of the catalytic oxidation. The linear dynamic range of the determination of Cr(III) was 1-40.0 μg/L, while the limit of detection was 0.05 μg/L. The correlation coefficient r was 0.998, while the relative standard deviation for 5 μg/L of the Cr(III) solution was 3.83%. The feasibility of this method was checked by its application to trivalent chromium determination in real water samples.

  11. Extraction and analysis of lead in sweeteners by flow-injection Donnan dialysis with flame atomic absorption spectroscopy.

    Science.gov (United States)

    Antonia, A; Allen, L B

    2001-10-01

    Flow-injection Donnan dialysis is demonstrated for the extraction of lead in sweeteners using flame atomic absorption spectroscopy (FAAS). For spiked concentrations in the low microgram per gram range, recoveries were greater than 90%, and the relative standard deviation was typically less than 10% for a 15-min dialysis procedure. The method detection limit is 350 ng/g. Donnan dialysis is shown to be successful for the extraction of lead in sucrose, corn syrup, and honey but limited in performance for molasses and artificial syrup. This paper also includes a comparison to other procedures for the determination of lead in sweeteners and presents options for realizing improved method performance with Donnan dialysis.

  12. Flow-injection chemiluminescence determination of acetylsalicylic acid based on its enhancing effect on the lucigenin–hydrogen peroxide system.

    Science.gov (United States)

    Wabaidur, S M; Alam, S M; Alothmana, Z A; Eldesokya, Gaber

    2014-09-01

    A sensitive flow-injection chemiluminescence method for the determination of acetylsalicylic acid is described. It is based on the enhanced chemiluminescent emission of the alkaline lucigenin–H2O2 system by acetylsalicylic acid. The difference in chemiluminescent intensity of alkaline lucigenin–H2O2 in the presence of acetylsalicylic acid from that in the absence of acetylsalicylic acid was linear at acetylsalicylic acid concentrations in the range of 0.0029–47.37 μg/mL, with detection and quantification limits of 0.0011 and 0.0029 μg/mL, respectively. The correlation coefficient of the working curve was 0.9983. The relative standard deviation (n = 10) for 25 μg/mL acetylsalicylic acid is 1.95%. All experimental parameters were optimized. The method was successfully applied to the determination of acetylsalicylic acid in pharmaceutical preparations. The recovery results obtained by the method were satisfactory.

  13. Simple flow injection colorimetric system for determination of paraquat in natural water.

    Science.gov (United States)

    Chuntib, Prakit; Jakmunee, Jaroon

    2015-11-01

    A simple and low cost flow injection colorimetric system has been developed for determination of paraquat in natural water. The developed method is based on the reduction of paraquat by using sodium dithionite as a reducing agent in an alkaline medium to produce a blue free radical ion that can be detected by a simple light emitting diode-light dependent resistor (LED-LDR) colorimeter. The standard or sample solution was injected via a set of 3-way solenoid valves into a water carrier stream and flowed to merge with reagent to generate a colored product which is proportional to the concentration of paraquat ion in the solution. Under the optimum condition of the system, i.e., mixing coil length 30 cm, flow rate 2.0 mL min(-1), sample volume 100 μL, concentrations of dithionite 0.1% (w/v) and sodium hydroxide 0.06 mol L(-1), a linear calibration graph in the range of 0.2-10.0 mg L(-1) with a correlation coefficient of 0.9996, and a limit of detection of 0.15 mg L(-1) were achieved. Relative standard deviation for 9 replicate injections of 1 mg L(-1) paraquat is 3.7%. A sample throughput of 40 injections h(-1) was achieved. The limit of detection can be improved by off-line preconcentration of paraquat employing a column packed with Dowex 50WX8-100 (H) cation exchange resin and eluted with 10% (w/v) ammonium chloride in ammonium buffer solution pH 10. The eluting solution was then injected into the FI system for paraquat determination. The proposed system did not suffer from interferences of some possible ions in natural water and other herbicides. Recoveries obtained by spiking 0.5 and 5.0 mg L(-1) paraquat standard into water samples were in the range of 104-110% and 101-105%, respectively. The developed system can be conveniently applied for screening of paraquat contaminated in natural water.

  14. Novel amperometric glucose biosensor based on MXene nanocomposite

    KAUST Repository

    Rakhi, R. B.

    2016-11-10

    A biosensor platform based on Au/MXene nanocomposite for sensitive enzymatic glucose detection is reported. The biosensor leverages the unique electrocatalytic properties and synergistic effects between Au nanoparticles and MXene sheets. An amperometric glucose biosensor is fabricated by the immobilization of glucose oxidase (GOx) enzyme on Nafion solubilized Au/ MXene nanocomposite over glassy carbon electrode (GCE). The biomediated Au nanoparticles play a significant role in facilitating the electron exchange between the electroactive center of GOx and the electrode. The GOx/Au/MXene/Nafion/GCE biosensor electrode displayed a linear amperometric response in the glucose concentration range from 0.1 to 18 mM with a relatively high sensitivity of 4.2 μAmM−1 cm−2 and a detection limit of 5.9 μM (S/N = 3). Furthermore, the biosensor exhibited excellent stability, reproducibility and repeatability. Therefore, the Au/MXene nanocomposite reported in this work is a potential candidate as an electrochemical transducer in electrochemical biosensors.

  15. BIENZYME REACTOR FOR ELECTROCHEMICAL DETECTION OF LOW CONCENTRATIONS OF URIC-ACID AND GLUCOSE

    NARCIS (Netherlands)

    ELEKES, O; MOSCONE, D; VENEMA, K; KORF, J

    1995-01-01

    An enzyme-based flow-injection amperometric analysis system (FIA) for monitoring of uric acid and glucose is described, The oxidase and peroxidase enzymes are physically co-immobilised in a sandwich-type reactor and ferrocene serves as a mediator. The assays are based on the measurement of a reducti

  16. 高效阴离子交换-脉冲安培法测定化妆品中葡萄糖酸锌含量%DETERMINATION OF ZINC GLUCONATE IN COSMETICS BY HIGH PERFORMANCE ION EXCHANGE CHROMATOGRAPHY WITH PULSED AMPEROMETRIC DETECTION

    Institute of Scientific and Technical Information of China (English)

    施超欧; 丁卉; 刘菊; 王荣; 杨柳

    2012-01-01

    A new practical method for determination of zinc gluconate in cosmetics by high performance ion exchange chromatography with pulsed amperometric detection was established. The sample was prepared by removing the hydrophobic components with On Guard II RP column after extracting by the ultra pure water. The sample was separated by connecting the CarboPac PA20 guard column and CarboPac PA1 guard column in series and detected by pulsed amperometric detection. The linear range was 0.1~5.0mg/L (r2=0.9999) for zinc gluconate and the recovery was 98.9~107.7%. The detection limit of zinc gluconate in sample was 4.2mg/kg while the detection limit of method was 0.042mg/L. High performance and good sensitivity was obtained.%建立了高效阴离子交换-脉冲安培法测定化妆品中葡萄糖酸锌的含量.样品用水超声提取后,离心取上清液过On Guard Ⅱ RP柱除去疏水性化合物,再经CarboPac PA1和CarboPacPA20保护柱分离,脉冲安培检测,葡萄糖酸锌在0.1~5.0mg/L范围内线性关系良好(r2=0.9999),加标回收率在98.9~107.7%之间,方法检出限为0.042mg/L,对应样品中检出限为4.2mg/kg,方法简单,灵敏度高.

  17. Recent Development in Optical Chemical Sensors Coupling with Flow Injection Analysis

    Directory of Open Access Journals (Sweden)

    Fuensanta Sánchez Rojas

    2006-10-01

    Full Text Available Optical techniques for chemical analysis are well established and sensors based on thesetechniques are now attracting considerable attention because of their importance in applications suchas environmental monitoring, biomedical sensing, and industrial process control. On the other hand,flow injection analysis (FIA is advisable for the rapid analysis of microliter volume samples and canbe interfaced directly to the chemical process. The FIA has become a widespread automatic analyticalmethod for more reasons; mainly due to the simplicity and low cost of the setups, their versatility, andease of assembling. In this paper, an overview of flow injection determinations by using opticalchemical sensors is provided, and instrumentation, sensor design, and applications are discussed. Thiswork summarizes the most relevant manuscripts from 1980 to date referred to analysis using opticalchemical sensors in FIA.

  18. Determination of Ciprofloxacin by Flow Injection Analysis Based on Chemiluminescence System

    Institute of Scientific and Technical Information of China (English)

    2006-01-01

    A novel flow injection chemiluminescence (CL) method for the determination of ciprofloxacin (CPLX) was reported. The proposed method is based on luminescence produced by KMnO4-Na2S2O4-Tb3+-CPLX chemiluminescence (CL) system. The effects of some critical experimental conditions were discussed and the optimization of working condithe recoveries of real sample analyses were in the range from 110 ± 4 to 104 ± 4.

  19. Theoretical considerations of Flow Injection Analysis in the Absence of Chemical Reactions

    DEFF Research Database (Denmark)

    Andersen, Jens Enevold Thaulov

    2000-01-01

    The fundamental mechanism of flow injection analysis (FIA) is assumed to be simple dissusion and the response of the detector is included in a model description that provide information about the shape of the FIA peak in terms of, basically, five parameters. Two of the five parameters are associa...... that any deviation from the features of the present model and the results of a tentative chemical reaction with one of the test compounds, is related to chemical kinetics....

  20. Micelle-mediated methodology for the preconcentration of uranium prior to its determination by flow injection

    Energy Technology Data Exchange (ETDEWEB)

    Fernandez Laespada, M.E.; Perez Pavon, J.L.; Moreno Cordero, B. (Univ. de Salamanca (Spain). Dept. de Quimica Analitica, Nutricion y Bromatologia)

    1993-02-01

    Cloud point extraction has been used for the preconcentration of uranium, prior to its determination by flow injection. The non-ionic surfactant employed was Triton X-114 and the reagent chosen to form a hydrophobic chelate of uranium was 1-(2-pyridylazo)-2-naphthol. The optimum conditions for the preconcentration and determination of uranium have been studied. This methodology has been applied to the determination of trace amounts of uranium in tap and river waters from Salamanca. (Author).

  1. Study on the luminescence behavior of lanthanide ions with luminol by flow injection chemiluminescence analysis

    Energy Technology Data Exchange (ETDEWEB)

    Liu, Xiaoqing [College of Chemistry and Material Science, Northwest University, 710069 Xi' an (China); Wang, Zhuming [College of Earth Sciences and Land Resources, Chang' an University, 710054 Xi' an (China); Li, Yajuan [College of Chemistry and Material Science, Northwest University, 710069 Xi' an (China); Zhang, Yun [Department of pharmacy, Xi' an Medical University, 710021 Xi' an (China); Guo, Jie; Zhao, Jingchan [College of Chemistry and Material Science, Northwest University, 710069 Xi' an (China); Song, Zhenghua, E-mail: songzhenghua@hotmail.com [College of Chemistry and Material Science, Northwest University, 710069 Xi' an (China)

    2015-06-15

    This work first described the linear quenching of Ln{sup III} (including La{sup III}, Ce{sup III}, Pr{sup III}, Nd{sup III}, Sm{sup III}, Eu{sup III}, Gd{sup III}, Tb{sup III}, Dy{sup III}, Ho{sup III}, Er{sup III}, Tm{sup III}, Yb{sup III} and Lu{sup III}) on luminol–dissolved oxygen chemiluminescence system and possible quenching mechanism by flow injection analysis. The general equation of the decrement of CL intensity with Ln{sup III} concentration, ΔI=AlnC{sub Ln}+B, was given and the interaction model of Ln{sup III} with luminol, lg[(I{sub 0}−I)/I]=rlg[Ln]+lgK, was established. The sensitive factor A was found to be linear with the physical parameters (Z, γ{sub ±}, E{sup o} and ΔH{sub hyd}). By plotting A against Z, it could be seen light lanthanides (LL) and heavy lanthanides (HL) presented a good symmetry. The results showed that the reaction of Ln{sup III} with luminol was a spontaneous process by the electrostatic force with the association constants K at 10{sup 6}–10{sup 7} level. The binding constants K{sub D} (about 10{sup 4}–10{sup 5}) and the number of binding sites n (about 1) of Ln{sup III} (La{sup III}, Eu{sup III}, Gd{sup III}, Tb{sup III} and Lu{sup III}) to bovine serum albumin were first given by FI–CL, and the binding ability of Ln{sup III} followed the pattern: La{sup III}detecting Ln{sup III} with luminol.

  2. An Investigation of Glutathione-Platinum(II Interactions by Means of the Flow Injection Analysis Using Glassy Carbon Electrode

    Directory of Open Access Journals (Sweden)

    Rene Kizek

    2007-07-01

    Full Text Available Despite very intensive research in the synthesising of new cytostatics, cisplatin isstill one of the most commonly used anticancer drugs. Therefore, an investigation ofinteractions of cisplatin with different biologically important amino acids, peptides andproteins is very topical. In the present paper, we utilized flow injection analysis coupledwith electrochemical detection to study and characterize the behaviour of various forms ofglutathione (reduced glutathione – GSH, oxidized glutathione – GSSG and S-nitrosoglutathione – GSNO. The optimized conditions were as follows: mobile phase consistedof acetate buffer (pH 3 with a flow rate of 1 mL min-1. Based on results obtained we chose850 mV as the optimal potential for detection of GSH and 1,100 mV as the optimalpotential for detection of GSSG and GSNO. The detection limits of GSH, GSSG andGSNO were 100 pg mL-1, 50 ng mL-1 and 300 pg mL-1, respectively. Further, the optimized technique was used for investigation of interactions between cisplatin and GSH. We were able to observe the interaction between GSH and cisplatin via decrease in the signal corresponding to glutathione. Moreover, we evaluated the formation of the complex by spectrometry. The spectrometric results obtained were in good agreement with electrochemical ones.

  3. Application of Ionic Liquids in Amperometric Gas Sensors.

    Science.gov (United States)

    Gębicki, Jacek; Kloskowski, Adam; Chrzanowski, Wojciech; Stepnowski, Piotr; Namiesnik, Jacek

    2016-01-01

    This article presents an analysis of available literature data on metrological parameters of the amperometric gas sensors containing ionic liquids as an electrolyte. Four mechanism types of signal generation in amperometric sensors with ionic liquid are described. Moreover, this article describes the influence of selected physico-chemical properties of the ionic liquids on the metrological parameters of these sensors. Some metrological parameters are also compared for amperometric sensors with GDE and SPE electrodes and with ionic liquids for selected analytes.

  4. THE STUDY OF INTERACTION OF SOLID-LIQUID ADSORPTION SYSTEM BY USING THE FLOW INJECTION-SPECTROPHOTOMETRY SYSTEM

    Institute of Scientific and Technical Information of China (English)

    2001-01-01

    The flow injection analysis was firstly used for studying a solid-liquid adsorption system,and the dynamics process in the adsorption of dyestuff with regenerable chitin was traced by an online method of flow injection-spectrophotometry. Experimental results indicate that there is a linearization between the tested signals and the height of peaks with reciprocity coefficient 0.9999by using the flow injection-spectrophotometry system to study the dynamics adsorption process in solid-liquid system. The method shows a good stability and reproducibility. It provides a new method for the studies on adsorption dynamics in solid- liquid system.

  5. Replacing immunoassays for mephedrone, ketamines and six amphetamine-type stimulants with flow injection analysis tandem mass spectrometry.

    Science.gov (United States)

    Lua, Ingrid A; Lin, Shiou-Ling; Lin, Huei R; Lua, Ahai C

    2012-10-01

    A screening procedure was developed for the simultaneous detection of mephedrone, six amphetamine-type stimulants (ATS), ketamine and its two metabolites with electrospray ionization flow injection analysis tandem mass spectrometry (FIA-MS-MS). Urine samples were fortified with deuterated analogues as internal standards, extracted with ethyl acetate and analyzed with FIA-MS-MS. The mass analyzer was operated in multiple reaction monitoring mode. Two product ions were monitored for each drug and internal standards. For each analyte, the limit of detection was less than 4 µg/L, within-day and between-day precisions (percent coefficient of variation) at three different concentrations were less than 7.3% and bias was between -17.3 and 11.8%. Total analysis time with FIA-MS-MS is 1.8 min per sample. A group of 215 urine samples were screened with immunoassay for ATS and analyzed with FIA-MS-MS and gas chromatography-mass spectrometry (GC-MS) for ketamines and ATS. The analysis of ATS by immunoassay and GC-MS was 96.7% concordant. The analysis of three ketamines and seven ATS by FIA-MS-MS and GC-MS was 97.2% concordant. The FIA-MS-MS procedure is efficient, accurate, flexible and capable of detecting analytes of different chemical groups. It can replace immunoassays for the screening of new designer drugs when commercial immunoassays are unavailable.

  6. A flow injection system for the spectrophotometric determination of lead after preconcentration by solid phase extraction onto Amberlite XAD-4

    Directory of Open Access Journals (Sweden)

    Jintana Klamtet

    2008-07-01

    Full Text Available An on-line flow injection analysis (FIA system for determination of lead (II in water samples with a preconcentration step and spectrophotometric detection was investigated. The system is based on preconcentration of lead (II on a column packed with Amberlite XAD-4 resin and detection by means of 4-(2-pyridylazoresorcinol (PAR–lead complex formation with maximum absorption at 523 nm. Chemical and FIA variables influencing performance of the system were optimised. Two linear calibration curves with a range of 0.01 - 0.40 and 0.40 – 0.80 mg L-1 were obtained. The developed system allowed a throughput rate of 16 samples h-1 with a 9-fold enrichment factor and a detection limit of 7 µg L-1. Relative standard deviation for 10 replicated injections of 0.25 mg L-1 was 2.3%. Recoveries of the method were in the range of 80-94 %. The procedure was validated by analysis of lead (II in real water samples, and the results were statistically compared with those obtained by flame atomic absorption spectrophotometry (FAAS. The results obtained both by the proposed method and by FAAS were in good agreement.

  7. Numerical model based on amperometric measurements

    OpenAIRE

    Daungruthai Jarukanont; Imelda Bonifas Arredondo; Ricardo Femat; Garcia, Martin E.

    2015-01-01

    Chromaffin cells release catecholamines by exocytosis, a process that includes vesicle docking, priming and fusion. Although all these steps have been intensively studied, some aspects of their mechanisms, particularly those regarding vesicle transport to the active sites situated at the membrane, are still unclear. In this work, we show that it is possible to extract information on vesicle motion in Chromaffin cells from the combination of Langevin simulations and amperometric measurements. ...

  8. Simultaneous Determination of Gold and Platinum by Double Artificial Neural Network Analysis with Flow-injection Chemiluminescence

    Institute of Scientific and Technical Information of China (English)

    Ming Yang LIU; Hai Tao ZHANG; Jun Feng LI; Shu Gui CHEN; Hong Yan WANG

    2006-01-01

    A highly sensitive double artificial neural network (DANN) analysis with flow-injection chemiluminescence (FI-CL) has been developed to simultaneously determine the trace amounts of the gold and platinum in simulated mixed samples, without the boring process.

  9. Amperometric and impedance monitoring systems for biomedical applications

    CERN Document Server

    Punter-Villagrasa, Jaime; del Campo, Francisco J; Miribel, Pere

    2017-01-01

    The book presents the conception and realization of a pervasive electronic architecture for electrochemical applications, focusing on electronic instrumentation design and device development, particularly in electrochemical Point-of-Care and Lab-on-a-Chip devices, covering examples based on amperometric (DC) and impedance detection (AC) techniques. The presented electronics combine tailored front-end instrumentation and back-end data post-processing, enabling applications in different areas, and across a variety of techniques, analytes, transducers and environments. It addresses how the electronics are designed and implemented with special interest in the flow process: starting from electronic circuits and electrochemical biosensor design to a final validation and implementation for specific applications. Similarly, other important aspects are discussed throughout the book, such as electrochemical techniques, different analytes, targets, electronics reliability and robustness. The book also describes the use ...

  10. Measurement system for nitrous oxide based on amperometric gas sensor

    Science.gov (United States)

    Siswoyo, S.; Persaud, K. C.; Phillips, V. R.; Sneath, R.

    2017-03-01

    It has been well known that nitrous oxide is an important greenhouse gas, so monitoring and control of its concentration and emission is very important. In this work a nitrous oxide measurement system has been developed consisting of an amperometric sensor and an appropriate lab-made potentiostat that capable measuring picoampere current ranges. The sensor was constructed using a gold microelectrode as working electrode surrounded by a silver wire as quasi reference electrode, with tetraethyl ammonium perchlorate and dimethylsulphoxide as supporting electrolyte and solvent respectively. The lab-made potentiostat was built incorporating a transimpedance amplifier capable of picoampere measurements. This also incorporated a microcontroller based data acquisition system, controlled by a host personal computer using a dedicated computer program. The system was capable of detecting N2O concentrations down to 0.07 % v/v.

  11. Novel miniaturized sensors for potentiometric batch and flow-injection analysis (FIA) of perchlorate in fireworks and propellants.

    Science.gov (United States)

    Almeer, Saeed H M A; Zogby, Ibrahim A; Hassan, Saad S M

    2014-11-01

    Three planar miniaturized perchlorate membrane sensors (3×5 mm(2)) are prepared using a flexible Kaptan substrate coated with nitron-perchlorate (NT-ClO4) [sensor 1], methylene blue-perchlorate (MB-ClO4) [sensor II] and indium-porphyrin (In-Por) [sensor III] as electroactive materials in PVC membranes plasticized with 2-NPPE. Sensors I, II and III display near-Nernstian response for 1.0×10(-5)-1.0×10(-2), 3.1×10(-5)-1.0×10(-2) and 3.1×10(-6)-1.0×10(-2) mol L(-1) ClO4(-) with lower detection limits of 6.1×10(-6), 6.9×10(-6) and 1.2×10(-6) mol L(-1), and anionic calibration slopes of 50.9±0.4, 48.4±0.4 and 57.7±0.3 mV decade(-1), respectively. Methods for determining perchlorate using these sensors offer many attractive advantages including simplicity, flexibility, cost effectiveness, wide linear dynamic response range (0.1-1000 ppm), low detection limit (sensors show high selectivity in the presence of some inorganic ions (e.g., PO4(3-), SO4(2-), S2O3(2-), NO2(-), NO3(-), N3(-), CN(-), Cl(-), Br(-), I(-)) and automation feasibility. Indium-porphyrin based membrane sensor (sensor III) is used as a detector in a wall-jet flow injection set-up to enable accurate flow injection analysis (FIA) of perchlorate in some fireworks without interferences from the associated reducing agents (sulfur and charcoal), binders (dextrin, lactose), coloring agents (calcium, strontium, copper, iron, sodium), color brighten (linseed oil) and regulators (aluminum flakes) which are commonly used in the formulations. The sensor is also used for perchlorate assessment in some propellant powders. The results fairly agree with data obtained by ion-chromatography.

  12. Multisyringe flow injection analysis of stable and radioactive strontium in samples of environmental interest.

    Science.gov (United States)

    Fajardo, Y; Gómez, E; Mas, F; Garcias, F; Cerdà, V; Casas, M

    2004-01-01

    A multisyringe flow injection (MSFIA) method for the determination of stable and radioactive strontium, using a solid phase resin (Sr-Resin), has been developed. Strontium concentrations are determined by atomic emission spectroscopy and by a low background proportional counter. The method has been applied to different samples (water, milk and soil) of environmental interest. The LLD of the stable and radioactive Sr were 10 microg/l and 0.01 Bq, respectively. The standard deviation of the separation procedure is 2% (n=10).

  13. The potentials of the third generation of flow injection analysis for nutrient monitoring and fractionation analysis

    DEFF Research Database (Denmark)

    Miró, Manuel; Hansen, Elo Harald; Buanuam, Janya

    2006-01-01

    In the present communication, the third generation of flow injection analysis, the so-called micro sequential-injection Laboratory-on-Valve (μSI-LOV), is presented as a miniaturized, automated approach for on-line monitoring of nutrients in different environmental compartments as effected under...... enclosed and strictly controlled conditions. Special emphasis is placed on coupling μSI-LOV on-line with a recently developed microcolumn to perform dynamic fractionation schemes for ascertaining the availability of phosphorous forms in solid substrates for biota uptake under simulated environmental...

  14. Method for 236U Determination in Seawater Using Flow Injection Extraction Chromatography and Accelerator Mass Spectrometry

    DEFF Research Database (Denmark)

    Qiao, Jixin; Hou, Xiaolin; Steier, Peter;

    2015-01-01

    An automated analytical method implemented in a flow injection (FI) system was developed for rapid determination of 236U in 10 L seawater samples. 238U was used as a chemical yield tracer for the whole procedure, in which extraction chromatography (UTEVA) was exploited to purify uranium, after......, on the basis of studying the coprecipitation behavior of uranium with iron hydroxide. The analytical results indicate that the developed method is simple and robust, providing satisfactory chemical yields (80−100%) and high analysis speed (4 h/sample), which could be an appealing alternative to conventional...... manual methods for 236U determination in its tracer application....

  15. On the possibility to improve the performance of flow injection analysis by deconvolution of spectrophotometric data

    DEFF Research Database (Denmark)

    Andersen, Jens Enevold Thanulov

    2001-01-01

    The concentration profile of chemical species pumped through a tubular system of 0.5 mm inner diameter is found to be trapezial shaped, as described theoretically by including the spatial resolution of the instrument, friction and diffusion. By applying the theory, which is based on the concept...... of segment flow, to experiments, it is shown that an injected segment of solute is diluted predominantly at the front and at the tail proportion of the segment in motion. A double-peaked structure in experiments of Flow-Injection Analysis (FIA) was identified and by including all the data...

  16. DETERMINATION OF TETRACYCLINE AND OXYTETRACYCLINE BY FLOW-INJECTION CHEMILUMINESCENCE METHOD

    Institute of Scientific and Technical Information of China (English)

    2006-01-01

    Tetracycline and oxytetracycline are broad-spec-trumantibiotics.They are not only used in humanpathologies,but alsoin veterinary medicine,ani malnutrition and feed additives for cattle breeding.In the past few years,the deter mination meth-ods of tetracycline and oxytetracycline were repor-ted,which involved in difference spectrophotome-try[1],HPLC[2,3],spectrophotometry[4-7],HPLC-MS[8-9],spectrofluori metry[10],solid-phase extrac-tion[11]and kinetic methods.Recently,flow-injection CL method has beenpaid mo...

  17. Flow-injection-enhanced chemiluminescence method for the determination of three β-blockers

    Institute of Scientific and Technical Information of China (English)

    2010-01-01

    Objective To develop a rapid,simple and sensitive chemiluminescence method for the determination of three β-blockers (bisoprolol,atenolol and propranolol). Methods The chemiluminescence of cerium (Ⅳ)-sulfite system was obviously sensitized by adding anyone of three β-blockers in acid media. A new chemiluminescence method was set up by combining with flow-injection technique and used to determine the three β-blockers. Results Good linear ranges were obtained at the concentrations of 2.0×10-7g/mL-4.0×10-5g/mL...

  18. Flow injection determination of Se in dietary supplements using TiO2 mediated ultraviolet-photochemical volatile species generation

    Science.gov (United States)

    Nováková, E.; Linhart, O.; Červený, V.; Rychlovský, P.; Hraníček, J.

    2017-08-01

    This paper proposes a method for determination of selenium content in samples of dietary supplements using TiO2 mediated UV-photochemical vapor generation with quartz furnace atomic spectrometric detection. The flow-injection method was optimized for determination of selenium in the form of selenite or selenate ions. The limits of detection of the proposed method are 0.89 ng mL- 1 and 0.68 ng mL- 1 for selenite and selenate, respectively. Extraction in neutral medium was used for the leaching of selenate and NaOH solution was used for the leaching of selenite. The methods accuracy was verified against the declared amounts of Se in five different samples of over-the-counter dietary supplements and on NIST SRM 3280. The method was also compared to results achieved with determination by electrothermal atomization atomic absorption spectrometry following microwave decomposition. The recovery of selenium during sample preparation was tested by spiking the tablets prior to extraction and estimated to be approximately 100%. An interference study has been carried out to estimate the effect of concomitant elements on the methods accuracy.

  19. Flow-injection chemiluminescence determination of phentolamine based on its enhancing effect on the luminol-potassium ferricyanide system.

    Science.gov (United States)

    Huang, Yuming; Liu, Weibing

    2005-07-01

    It was found that the light emission produced by the oxidation of luminol by potassium ferricyanide in the basic medium was enhanced by phentolamine, a drug recently used to treatment of male and female sexual dysfunction. The optimum conditions for this chemiluminescent reaction were studied in detail by a flow-injection system. A new, simple and rapid method has been developed under the optimum conditions for determination of phentolamine. This method has the advantages of high sensitivity, good reproducibility and low detection limit. On the basis of investigation of chemiluminescent, fluorescent and UV spectra of phentolamine in basic solution containing potassium ferricyanide and luminol, a possible mechanism of this reaction was proposed. In the optimum conditions, CL intensities are proportional to concentrations of the phentolamine in the 0.01-1 microg/mL range. The limit of detection is 3.0 ng/mL for phentolamine. The method has been applied to the determination of phentolamine in the commercial preparations, synthetic samples and biological fluids with satisfactory results.

  20. Flow injection analysis of chemical oxygen demand (COD) by using a boron-doped diamond (BDD) electrode.

    Science.gov (United States)

    Yu, Hongbin; Ma, Chuanjun; Quan, Xie; Chen, Shuo; Zhao, Huimin

    2009-03-15

    A simple, environmentally friendly and continuous flow method was developed for the determination of COD based on a flow injection analysis (FIA) system, in which a BDD electrode was employed as the detecting element. The structure and the electrochemical behavior of BDD were investigated by a scanning electron microscope, Raman spectroscopy, and cyclic voltammetry, respectively. The results demonstrated thatthe high-quality BDD film prepared here was suitable to be used as an electrode, with which the COD measurement could be conducted. The effect of several important experimental parameters, such as applied potentials, pH, flow rates, and supporting electrolyte concentrations, on the analytical performance was investigated. Under optimized testing conditions, the proposed method was successfully applied in the COD analysis of synthetic samples. The linear range and the detection limit were 2-175 and 1 mg L(-1), respectively. In addition, the COD values determined by the proposed method compared well with those analyzed bythe conventional method as demonstrated by small relative errors.

  1. Flow injection conductometric system with gas diffusion separation for the determination of Kjeldahl nitrogen in milk and chicken meat.

    Science.gov (United States)

    Junsomboon, Jaroon; Jakmunee, Jaroon

    2008-10-10

    A simple flow injection (FI) conductometric system with gas diffusion separation was developed for the determination of Kjeldahl nitrogen (or proteins) in milk and chicken meat. The sample was digested according to the Kjeldahl standard method and the digest was diluted and directly injected into the donor stream consisting of 4M NaOH. In alkaline medium, ammonium was converted to ammonia, which diffused through the PTFE membrane to dissolve in an acceptor stream (water). Dissociation of ammonia caused a change in conductance of the acceptor solution, which was linearly proportional to the concentration of ammonium originally present in the injected solution. A conductometric flow through cell and an amplifier circuit was fabricated, which helped improve sensitivity of the conductometric detection system. With using a plumbing Teflon tape as a gas diffusion membrane and without thermostating control of the system, a linear calibration graph in range of 10-100mgL(-1) N-NH(4) was obtained, with detection limit of 1mgL(-1) and good precision (relative standard deviation of 0.3% for 11 replicate injections of 50mgL(-1) N-NH(4)). The developed method was validated by the standard Kjeldahl distillation/titration method for the analysis of milk and chicken meat samples. The proposed system had sample throughput of 35h(-1) and consumed much smaller amounts of chemical than the standard method (275mg vs 17.5g of NaOH per analysis, respectively).

  2. Flow injection on-line solid phase extraction for ultra-trace lead screening with hydride generation atomic fluorescence spectrometry.

    Science.gov (United States)

    Wan, Zhuo; Xu, Zhangrun; Wang, Jianhua

    2006-01-01

    A flow injection (FI) on-line solid phase extraction (SPE) procedure for ultra-trace lead separation and preconcentration was developed, followed by hydride generation and atomic fluorescence spectrometric (AFS) detection. Lead is retained on an iminodiacetate chelating resin packed microcolumn, and is afterward eluted with 2.5% (v/v) hydrochloric acid to facilitate the hydride generation by reaction with alkaline tetrahydroborate solution with 1% (m/v) potassium ferricyanide as an oxidizing (or sensitizing) reagent. The hydride was separated from the reaction medium in the gas-liquid separator and swept into the atomizer for quantification. The chemical variables and the FI flow parameters were carefully optimized. With a sample loading volume of 4.8 ml, quantitative retention of lead was obtained, along with an enrichment factor of 11.3 and a sampling frequency of 50 h(-1). A detection limit of 4 ng l(-1), defined as 3 times the blank standard deviation (3 sigma), was achieved along with a RSD value of 1.6% at the 0.4 microg l(-1) level. The procedure was validated by determining lead contents in two certified reference materials, and its practical applicability was further demonstrated by analysing a variety of biological and environmental samples.

  3. Microchip Capillary Electrophoresis with an End-Channel Amperometric Detector and Its Preliminary Application

    Institute of Scientific and Technical Information of China (English)

    吴友谊; 屈锋; 林金明

    2005-01-01

    An end-channel amperometric detector with a guide tube for working electrode was designed and integrated on a home-made glass microchip. The guide tube was directly patterned and fabricated at the end of the detection reservoir, which made the fixation and alignment of working electrode relatively easy. The fabrication was carried out in a two-step etching process. A 30 μm carbon fiber microdisk electrode and Pt cathode were also integrated onto the amperometric detector. The baseline separation of dopamine (DA), catechol (CA) and epinephrine (EP) was achieved within 80 s. Relative standard deviations of not more than 5.2% were obtained for both peak currents and migration times of DA and CA (n=5). Using standard adding method, DA in tLrine and plasma samples was detected. The recoveries were in the range of 83%—103%.

  4. Amperometric Determination of Sulfite by Gas Diffusion-Sequential Injection with Boron-Doped Diamond Electrode

    OpenAIRE

    Orawon Chailapakul; Toshihiko Imato; Narong Praphairaksit; Kulwadee Pinwattana; Chakorn Chinvongamorn

    2008-01-01

    A gas diffusion sequential injection system with amperometric detection using aboron-doped diamond electrode was developed for the determination of sulfite. A gasdiffusion unit (GDU) was used to prevent interference from sample matrices for theelectrochemical measurement. The sample was mixed with an acid solution to generategaseous sulfur dioxide prior to its passage through the donor channel of the GDU. Thesulfur dioxide diffused through the PTFE hydrophobic membrane into a carrier solution...

  5. A New Amperometric Glucose Biosensor with Naphthol Green B as Mediator

    Institute of Scientific and Technical Information of China (English)

    Qin ZHAO; Ruo YUAN; Chang Li MO; Ya Qin CHAI; Xia ZHONG

    2004-01-01

    Naphthol green B was used, for the first time, as a new mediator in an amperometric glucose biosensor. It is a good mediator, promoting electron transfer from glucose oxidase to graphite electrode. The biosensor shows high sensitivity to glucose at low potential with response time of 30 seconds. The linear range is from 1.5 to 18 μmol/L glucose with detection limit of 0.5 μmol/L glucose.

  6. Speciation of mercury in fish samples by flow injection catalytic cold vapour atomic absorption spectrometry.

    Science.gov (United States)

    Zhang, Yanlin; Adeloju, Samuel B

    2012-04-01

    A rapid flow injection catalytic cold vapour atomic absorption spectrometric (FI-CCV-AAS) method is described for speciation and determination of mercury in biological samples. Varying concentrations of NaBH(4) were employed for mercury vapour generation from inorganic and mixture of inorganic and organic (total) Hg. The presence of Fe(3+), Cu(2+) and thiourea had catalytic effect on mercury vapour generation from methylmercury (MeHg) and, when together, Cu(2+) and thiourea had synergistic catalytic effect on the vapour generation. Of the two metal ions, Fe(3+) gave the best sensitivity enhancement, achieving the same sensitivity for MeHg and inorganic Hg(2+). Due to similarity of resulting sensitivity, Hg(2+) was used successfully as a primary standard for quantification of inorganic and total Hg. The catalysis was homogeneous in nature, and it was assumed that the breaking of the C-Hg bond was facilitated by the delocalization of the 5d electron pairs in Hg atom. The extraction of MeHg and inorganic mercury (In-Hg) in fish samples were achieved quantitatively with hydrochloric acid in the presence of thiourea and determined by FI-CCV-AAS. The application of the method to the quantification of mercury species in a fish liver reference material DOLT-4 gave 91.5% and 102.3% recoveries for total and methyl mercury, respectively. The use of flow injection enabled rapid analysis with a sample throughput of 180 h(-1).

  7. A Numerical study for the efficacy of flow injection on the diminution of rudder cavitation

    Science.gov (United States)

    Seo, Dae Won; Lee, Seung-Hee; Kim, Hyo Chul; Oh, Jung Keun

    2010-06-01

    The complete avoidance of cavitation, as a result of gap flow between the fixed and movable portion of a horn type rudder system, is difficult. To reduce gap flow, it is a common practice to attach a half round prismatic bar that protrudes beyond the concave surface of the horn facing the gap and laid along the centerplane of the rudder. However the employment of such a device does not always yield satisfactory results. Previously, the authors have shown that a pair of blocking bars, attached on the convex surface of the movable portion, better enhance the blocking ability of gap flow to that of a single centre bar installed on the concave surface. This also circumvents difficulties that might occur in practical applications. In the present study, a series of numerical computations show that flow injected into the gap of a rudder may also block the flow within, without employment of any physical devices, such as a half circular bar. This study also shows that the combination of flow injection and blocking bars may result in the synergic augmentation of blocking efficiency of gap flow, as demonstrated in computations for a three dimensional rudder system.

  8. Development of mediated BOD biosensor system of flow injection mode for shochu distillery wastewater.

    Science.gov (United States)

    Oota, Shinichi; Hatae, Yuta; Amada, Kei; Koya, Hidekazu; Kawakami, Mitsuyasu

    2010-09-15

    Although microbial biochemical oxygen demand (BOD) sensors utilizing redox mediators have attracted much attention as a rapid BOD measurement method, little attempts have been made to apply the mediated BOD biosensors to the flow injection analysis system. In this work, a mediated BOD sensor system of flow injection mode, constructed by combining an immobilized microbial reactor with an electrochemical flow cell of three electrodes configuration, has been developed to estimate BOD of shochu distillery wastewater (SDW). It was demonstrated consequently that the mediated sensing was realized by employing phosphate buffer containing potassium hexacyanoferrate as the carrier. The output current was found to yield a peak with a sample injection, and to result from reoxidation of reduced mediator at the electrode. By employing the peak area as the sensor response, the effects of flow rate and pH of the carrier on the sensitivity were investigated. The sensor system using a microorganism of high SDW-assimilation capacity showed good performance and proved to be available for estimation of BOD of SDW.

  9. Chemiluminescent determination of vanadium(IV) using a cinchomeronic hydrazide-H{sub 2}O{sub 2} system and flow injection analysis

    Energy Technology Data Exchange (ETDEWEB)

    Pradana Perez, J.A. [Departamento de Ciencias Analiticas, Facultad de Ciencias, Universidad Nacional de Educacion a Distancia, c/Senda del Rey 9, 28040 Madrid (Spain); Alegria, J.S. Durand [Departamento de Ciencias Analiticas, Facultad de Ciencias, Universidad Nacional de Educacion a Distancia, c/Senda del Rey 9, 28040 Madrid (Spain); Hernando, P. Fernandez [Departamento de Ciencias Analiticas, Facultad de Ciencias, Universidad Nacional de Educacion a Distancia, c/Senda del Rey 9, 28040 Madrid (Spain)]. E-mail: pfhernando@ccia.uned.es; Sierra, A. Narros [Departamento de Ingenieria Quimica y del Medio Ambiente, Escuela Tecnica Superior de Ingenieros Industriales, Universidad Politecnica de Madrid, Madrid (Spain)

    2005-04-22

    This paper proposes a new chemiluminescent flow injection analysis (FIA) method for the determination of vanadium(IV) ions in aqueous media. The method is based on the chemiluminescent reaction that occurs between cinchomeronic hydrazide (CH) and hydrogen peroxide in a strongly alkaline medium, in which vanadium(IV) acts as a catalyst. The chemical and physical variables involved in the flow injection system are optimised using a modified simplex method. Vanadium ions can be detected in the 0.08 and 1.00 {mu}g mL{sup -1} range; the detection limit for a signal-to-noise ratio of 3 is 0.08 {mu}g mL{sup -1}. Great variations in the quantum yield were observed when cobalt(II), chromium(III), copper(II) and/or nickel(II) were present in the reaction medium. The proposed method is selective and simple, and can be successfully used to analyse water samples without the need for separation or preconcentration processes.

  10. Determination of Gallic Acid by Flow Injection Analysis Based on LuminoI-AgNO3-Ag NPs Chemiluminescence System

    Institute of Scientific and Technical Information of China (English)

    李世凤; 孙惠敏; 王东; 钱莉; 朱燕; 陶善军

    2012-01-01

    A novel flow injection procedure has been developed for the determination of gallic acid based on the en- hancement function for luminol-AgNO3-Ag NPs chemiluminescence (CL) system by gallic acid. The enhancement mechanism was proposed for the reinforcing effect of the gallic acid on the CL system. The UV-vis absorption spectrum and CL emission spectrum were applied to confirm the mechanism. The method is simple, rapid and sen- sitive with a detection limit of 5 × 10^-10 g.mL-l and a linear range of 8.0 × 10^-10- 1.0 × 10-7 g.mL-1. The relative standard deviation (RSD) is 1.3% for eleven measurements of 5 × 10^-8 g-mL-1 gallic acid. The method has been successfully applied to the determination of gallic acid in Chinese proprietary medicine--Jianmin Yanhou tablets and synthesized samples.

  11. A simple and selective spectrophotometric flow injection determination of trace amounts of ruthenium by catalytic oxidation of safranin-O.

    Science.gov (United States)

    Rezaei, Behzad; Keyvanfard, Mohsen

    2008-03-01

    In this work, a simple, selective and rapid flow injection method has been developed for determination of ruthenium. The method is based on its catalytic effect on the oxidation of safranin-O by metaperiodate. The reaction was monitored spectrophotometrically by measuring safranin-O absorbance at lambdamax=521. The reagents and manifold variables, which have influences on the sensitivity, were investigated and the optimum conditions were established. The optimized conditions made it possible to determine ruthenium in the ranges of 0.4-20.0 ng/mL (DeltaA=0.2819CRu+1.1840) and 20.0-100.0 ng/mL (DeltaA=0.0984CRu+7.9391) with a detection limit of 0.095 ng/mL and a sample rate of 30+/-5 samples/h. Relative standard deviation for the five replicate measurements was less than 1.84%. The proposed method has been successfully applied for analysis of ultra trace amounts of ruthenium in real samples.

  12. Miniaturized ionophore-based potentiometric sensors for the flow-injection determination of metformin in pharmaceutical formulations and biological fluids.

    Science.gov (United States)

    Khaled, Elmorsy; Kamel, Manal S; Hassan, Hassan N; Abd El-Alim, Sameh H; Aboul-Enein, Hassan Y

    2012-12-01

    Miniaturized potentiometric sensors based on β-cyclodextrins (β-CDs) are described for determination of metformin (Mf) in pharmaceutical preparations and biological fluids. Electrode matrix compositions are optimized on the basis of the nature and content of sensing ionophore, ionic sites and plasticizers. Coated wire electrodes (CWEs) modified with heptakis(2,3,6-tri-O-methyl)-β-CD, sodium tetrakis(4-fluorophenyl)borate (NaTFPB) and 2-fluorophenyl 2-nitrophenyl ether (f-NPE), work satisfactorily in the concentration range from 10(-6) to 10(-1) mol L(-1) with Nernstian compliance (55.7 ± 0.4 mV per decade activity) and a detection limit of 8 × 10(-7) mol L(-1). Incorporation of β-CD as a molecular recognition element improved the electrode sensitivity and selectivity due to encapsulation of Mf into the β-CD cavity (host-guest interaction). The developed electrodes have been successfully applied for the potentiometric determination of Mf under batch and flow injection analysis (FIA). FIA allows analysis of 90 samples per h offering the advantages of simplicity, accuracy and automation feasibility. The dissolution profile for metformin pharmaceutical samples (Cidophage®) was monitored using the proposed electrode in comparison with the official spectrophotometric methods. Characterization of the formed Mf-β-CD inclusion complexes is discussed in detail.

  13. A simple and selective spectrophotometric flow injection determination of trace amounts of ruthenium by catalytic oxidation of safranin-O

    Energy Technology Data Exchange (ETDEWEB)

    Rezaei, Behzad [Department of Chemistry, Isfahan University of Technology, Isfahan 84156-84111 (Iran, Islamic Republic of)], E-mail: rezaei@cc.iut.ac.ir; Keyvanfard, Mohsen [Faculty of Science, Majlesi Campus, Islamic Azad University, Isfahan (Iran, Islamic Republic of)

    2008-03-01

    In this work, a simple, selective and rapid flow injection method has been developed for determination of ruthenium. The method is based on its catalytic effect on the oxidation of safranin-O by metaperiodate. The reaction was monitored spectrophotometrically by measuring safranin-O absorbance at {lambda}{sub max} = 521. The reagents and manifold variables, which have influences on the sensitivity, were investigated and the optimum conditions were established. The optimized conditions made it possible to determine ruthenium in the ranges of 0.4-20.0 ng/mL ({delta}A = 0.2819C{sub Ru} + 1.1840) and 20.0-100.0 ng/mL ({delta}A = 0.0984C{sub Ru} + 7.9391) with a detection limit of 0.095 ng/mL and a sample rate of 30 {+-} 5 samples/h. Relative standard deviation for the five replicate measurements was less than 1.84%. The proposed method has been successfully applied for analysis of ultra trace amounts of ruthenium in real samples.

  14. Automatic determination of insolubles in lubricating oils by flow injection analysis employing an LED-photometer detector.

    Science.gov (United States)

    Pignalosa, Gustavo; Sixto, Alexandra; Knochen, Moisés

    2007-10-31

    A flow injection system is presented for the determination of the insolubles content in used lubricating oil samples. The system is based on the injection of an aliquot of the sample in a stream of organic solvent where it is dispersed, and measurement of the scattered radiation (measured as apparent absorbance) in the visible range (lambda=640nm). An LED-based photometer was used for this purpose. The whole system including sample injection and data acquisition was controlled by a personal computer. Calibration curves exhibited good linearity (h=0.415+/-0.016C+0.00+/-0.03, r(2)=0.9995, confidence level of 95%) in the range up to 2.68% (insolubles in pentane). Detection and quantification limits were respectively 0.07% and 0.16% (w/w). The method was validated by analysis of 25 real samples by the proposed method and the FTIR method finding high correlation. Waste generation and reactive consumption is much less than in the official method (ASTM D-893). The proposed method employs 25mL of kerosene per sample while the official method employs 200mL of pentane.

  15. Flow-injection technique for determination of uranium and thorium isotopes in urine by inductively coupled plasma mass spectrometry.

    Science.gov (United States)

    Benkhedda, Karima; Epov, Vladimir N; Evans, R Douglas

    2005-04-01

    A sensitive and efficient flow-injection (FI) preconcentration and matrix-separation technique coupled to sector field ICP-mass spectrometry (SF-ICP-MS) has been developed and validated for simultaneous determination of ultra-low levels of uranium (U) and thorium (Th) in human urine. The method is based on selective retention of U and Th from a urine matrix, after microwave digestion, on an extraction chromatographic TRU resin, as an alternative to U/TEVA resin, and their subsequent elution with ammonium oxalate. Using a 10 mL sample, the limits of detection achieved for 238U and 232Th were 0.02 and 0.03 ng L(-1), respectively. The accuracy of the method was checked by spike-recovery measurements. Levels of U and Th in human urine were found to be in the ranges 1.86-5.50 and 0.176-2.35 ng L(-1), respectively, well in agreement with levels considered normal for non-occupationally exposed persons. The precision obtained for five replicate measurements of a urine sample was 2 and 3% for U and Th, respectively. The method also enables on-line measurements of the 235U/238U isotope ratios in urine. Precision of 0.82-1.04% (RSD) was obtained for 235U/238U at low ng L(-1) levels, using the FI transient signal approach.

  16. FLOW INJECTION ANALYSIS SYSTEM COUPLED WITH ICP-EOS FOR DETERMINATION OF SOME METALLIC ELEMENTS IN DRINKING WATER

    Directory of Open Access Journals (Sweden)

    Cristina Dinu

    2009-06-01

    Full Text Available The European Drinking Water Directive (98/83/EC, transposed in Romanian Legislation as Low 458/2002, amended by Low 311/2004, imposes the limit of concentration for metallic elements in water intended for human consumption. The toxic metals arsenic and selenium are among these elements and the limit value is 10 μg/L. In the paper there are presented the working conditions for determination of As and Se from drinking water using modern techniques based on the fl ow injection-hydride generation with the inductively coupled plasma atomic emission spectrometry (FIAS-ICP-EOS. The analyses were performed on Optima 5300 DV Perkin Elmer equipment with FIAS 400 Flow Injection System, Perkin Elmer type. For the hydride generation two types of solution were used: 10% (v/v HCl as a carrier solution and 0.2 % NaBH4 in 0.05%NaOH solution as a reducing agent [1]. The treatment step of the samples and standard solutions consisted in reducing with mixed solutions of KI and ascorbic acid in acidic condition (HCl for As and only with HCl and high temperature for Se [2,3]. The paper contains the characteristic parameters of the methods, such as: low detection limit, quantifi cation limit, repeatability, precision, recovery, which were evaluated using Certifi ed Reference Materials for each element.

  17. Flow injection preconcentration system using a new functionalized resin for determination of cadmium and nickel in tobacco samples

    Energy Technology Data Exchange (ETDEWEB)

    Lemos, Valfredo Azevedo [Laboratorio de Quimica Analitica (LQA), Universidade Estadual do Sudoeste da Bahia, Campus de Jequie, Jequie-BA 45206-190 (Brazil)], E-mail: vlemos@uesb.br; Novaes, Cleber Galvao; Lima, Adriana da Silva; Vieira, Daniel Rodrigues [Laboratorio de Quimica Analitica (LQA), Universidade Estadual do Sudoeste da Bahia, Campus de Jequie, Jequie-BA 45206-190 (Brazil)

    2008-06-30

    A solid-phase extraction method combined with flow injection (FI) on-line flame atomic absorption spectrometry (FAAS) for the determination of cadmium and nickel in tobacco samples is presented. The 2-aminothiophenol functionalized Amberlite XAD-4 (AT-XAD) resin was synthesized by covalent coupling of the ligand with the copolymer through a methylene group. A minicolumn packed with AT-XAD was connected into the automated on-line preconcentration system. Elution of metal ions from minicolumn can be made with 0.50 mol L{sup -1} hydrochloric acid solution. With a consumption of 21.0 mL of sample solution, detection limits (3 s) of 0.3 (Cd) and 0.8 {mu}g L{sup -1} (Ni) were achieved at a sample throughput of 18 h{sup -1}. Enrichment factors (EF) of 99 (cadmium) and 43 (nickel) were obtained compared with the slope of the linear portion of the calibration curves before and after preconcentration. The contents of Cd and Ni in a certified reference material (NIST 1570a, spinach leaves) determined by the present method was in good agreement with the certified value. The developed procedure was also successfully applied to the determination of Cd and Ni in local tobacco samples.

  18. Flow Injection Photosensitized Chemiluminescence of Luminol with Cu(II-Rose Bengal: Mechanistic Approach and Vitamin A and C Determination

    Directory of Open Access Journals (Sweden)

    Muhammad Asgher

    2014-01-01

    Full Text Available Rose Bengal photosensitized flow injection chemiluminescence method is reported using luminol-Cu(II for the determination of vitamins A and C in pharmaceutical formulations. The reaction is based on the enhancement effect of analyte in the production of anion radicals of Rose Bengal (RB•− which rapidly interact with dissolved oxygen and generate superoxide anions radicals (O2•− and hydrogen peroxide (H2O2. Highly reactive hydroxyl radicals (•OH were produced via dismutation of H2O2 by catalyst (Cu2+. The generated superoxide anions radicals and hydroxyl radicals thus oxidize luminol in alkaline medium to generate strong chemiluminescence. The limit of detection (3s of the blank, n=6 of vitamins A and C and RB was found to be 0.008, 0.005, and 0.05 μg mL−1, respectively. The sample throughput of 70 h−1 for vitamins A and C and 30 h−1 for RB was found. Calibration curve was linear in the range of 0.05–15, 0.01–20, and 0.1–50 μg mL−1 for vitamins A and C and RB, respectively, with relative standard deviations (RSDs; n=3 in the range 1.6–3.6%. The method was successfully applied to pharmaceutical formulations and the results obtained were in good agreement with the labeled values.

  19. Separation and determination of four active anthraquinones in Chinese herbal preparations by flow injection-capillary electrophoresis.

    Science.gov (United States)

    Liu, Lihong; Fan, Liuyin; Chen, Hongli; Chen, Xingguo; Hu, Zhide

    2005-08-01

    A simple, rapid, and accurate method for the separation and determination of physcion, chrysophanol, aloe-emodin, and emodin in Rhubarb, Juemingzi, and Chinese herbal preparations was developed by combination of flow injection-capillary zone electrophoresis for the first time. The analysis was carried out using an unmodified fused-silica capillary (75 mm x 50 microm ID x 375 microm OD, effective separation length of 48 mm) and direct ultraviolet detection at 254 nm. By a series of optimization, the sample solvent consisted of NaOH (100 mmol/L) and ACN (1:1 v/v), and a running buffer composed of 15 mmol/L sodium borate - 12.5 mmol/L sodium dihydrogen phosphate - 42% v/v ACN (pH 10.1) was applied for the separation of the four anthraquinones. The separation was rapid and highly reproducible, with complete resolution of all four compounds within 6 min. The sample throughput rate could reach up to 12 per h. The repeatability (defined as relative standard deviation) was 4.45, 4.44, 4.34, 0.61% with peak height evaluation and 1.62, 0.89, 2.49, 2.19% with peak area evaluation for physcion, chrysophanol, aloe-emodin, and emodin, respectively.

  20. Flow injection chemiluminescence determination of lercanidipine based on N-chlorosuccinimide-eosin Y post-chemiluminescence reaction.

    Science.gov (United States)

    Wang, Guowei; Zhao, Fang; Gao, Ying

    2014-12-01

    A novel post-chemiluminescence (PCL) reaction was discovered when lercanidipine was injected into the CL reaction mixture of N-chlorosuccinimide with alkaline eosin Y in the presence of cetyltrimethylammonium bromide (CTAB), where eosin Y was used as the CL reagent and CTAB as the surfactant. Based on this observation, a simple and highly sensitive PCL method combined with a flow injection (FI) technique was developed for the assay of lercanidipine. Under optimum conditions, the CL signal was linearly related to the concentration of lercanidipine in the range 7.0 × 10(-10) to 3.0 × 10(-6)  g/mL with a detection limit of 2.3 × 10(-10) g/mL (3σ). The relative standard deviation (RSD) was 2.1% for 1.0 × 10(-8) g/mL lercanidipine (n = 13). The proposed method had been applied to the estimation of lercanidipine in tablets and human serum samples with satisfactory results. The possible CL mechanism is also discussed briefly.

  1. Flow injection chemiluminescence sensor based on core-shell magnetic molecularly imprinted nanoparticles for determination of sulfadiazine.

    Science.gov (United States)

    Lu, Fuguang; Li, Huaijiang; Sun, Min; Fan, Lulu; Qiu, Huamin; Li, Xiangjun; Luo, Chuannan

    2012-03-09

    A novel flow injection chemiluminescence (FI-CL) sensor for determination of sulfadiazine (SDZ) using core-shell magnetic molecularly imprinted polymers (MMIPs) as recognition element is developed. Briefly, a hydrophilic MMIPs layer was produced at the surface of Fe(3)O(4)@SiO(2) magnetic nanoparticles (MNPs) via combination of molecular imprinting and reversible stimuli responsive hydrogel. And it provided the MMIPs with excellent adsorption capacity and rapid adsorption rate due to the imprinted sites mostly situated on the surface of MMIPs. Then the prepared SDZ-MMIPs were packed into flow cell to establish a novel FI-CL sensor. The sensor provided a wide linear range for SDZ of 4.0×10(-7) to 1.0×10(-4) mol L(-1) with a detection limit of 1.54×10(-7) mol L(-1). And the relative standard deviation (RSD) for the determination of 1.0×10(-6) mol L(-1) SDZ was 2.56% (n=11). The proposed method was applied to determine SDZ in urine samples and satisfactory results were obtained.

  2. Lanthanides determination in red wine using ultrasound assisted extraction, flow injection, aerosol desolvation and ICP-MS.

    Science.gov (United States)

    Bentlin, Fabrina R S; dos Santos, Clarissa M M; Flores, Erico M M; Pozebon, Dirce

    2012-01-13

    This paper deals with the determination of the fourteen naturally occurring elements of the lanthanide series in red wine. Ultrasound (US) was used for sample preparation prior lanthanides determination using ICP-MS. Flow injection (FI) and pneumatic nebulization/aerosol desolvation were used for nebulization of aliquots of 50 μL of sample and its subsequent transportation to plasma. Sample preparation procedures, matrix interference and time of sonication were evaluated. Better results for lanthanides in red wine were obtained by sonication with US probe for 90 s and sample 10-fold diluted. The limits of detection of La, Ce, Nd, Sm, Gd, Pr, Eu, Tb, Dy, Ho, Er, Tm, Lu and Yb were 6.57, 10.8, 9.97, 9.38, 2.71, 1.29, 1.22, 0.52, 2.35, 0.96, 2.30, 0.45, 0.24 and 1.35 ng L(-1), respectively. Red wines of different varieties from three countries of South America were discriminated according to the country of origin by means of multivariate analysis of lanthanides concentration. Copyright © 2011 Elsevier B.V. All rights reserved.

  3. Separation and determination of aloperine, sophoridine, matrine and oxymatrine by combination of flow injection with microfluidic capillary electrophoresis.

    Science.gov (United States)

    Cheng, Yuqiao; Chen, Hongli; Li, Yuqin; Chen, Xingguo; Hu, Zhide

    2004-05-28

    A novel, rapid and accurate method for the separation and determination of aloperine (ALP), sophoridine (SRI), matrine (MT) and oxymatrine (OMT) has been developed by combination of flow injection (FI) with microfluidic capillary electrophoresis (CE) for the first time. In the present paper, a continuous sample introduction interface was described. The interface with an H-channel structure was produced using a non-lithographic approach. The H-channel structure was fixed on a planar plastic base utilizing a horizontal 6.5cm-long separation capillary with two vertical sidearm tubes on each end that served as inlet and outlet flow-through electrode reservoirs. The inlet reservoir also functioned as interface for coupling to the FI system. The buffer solution used was a 50mmoll(-1) borate solution with the pH adjusted to 8.80 with 2moll(-1) HCl. The performance of the system was demonstrated in the separation and determination of ALP, SRI, MT and OMT with UV detection at 215nm, achieving baseline separation within 2min. A series of samples was injected repeatedly without current interruption and subsequent rinsing, and the contents of these four bio-alkaloids in two marketed drugs were determined with satisfactory recovery by this proposed method.

  4. Online spectrophotometric determination of Fe(II) and Fe(III) by flow injection combined with low pressure ion chromatography

    Science.gov (United States)

    Chen, Shujuan; Li, Nan; Zhang, Xinshen; Yang, Dongjing; Jiang, Heimei

    2015-03-01

    A simple and new low pressure ion chromatography combined with flow injection spectrophotometric procedure for determining Fe(II) and Fe(III) was established. It is based on the selective adsorption of low pressure ion chromatography column to Fe(II) and Fe(III), the online reduction reaction of Fe(III) and the reaction of Fe(II) in sodium acetate with phenanthroline, resulting in an intense orange complex with a suitable absorption at 515 nm. Various chemical (such as the concentration of colour reagent, eluant and reductive agent) and instrumental parameters (reaction coil length, reductive coil length and wavelength) were studied and were optimized. Under the optimum conditions calibration graph of Fe(II)/Fe(III) was linear in the Fe(II)/Fe(III) range of 0.040-1.0 mg/L. The detection limit of Fe(III) and Fe(II) was respectively 3.09 and 1.55 μg/L, the relative standard deviation (n = 10) of Fe(II) and Fe(III) 1.89% and 1.90% for 0.5 mg/L of Fe(II) and Fe(III) respectively. About 2.5 samples in 1 h can be analyzed. The interfering effects of various chemical species were studied. The method was successfully applied in the determination of water samples.

  5. Simultaneous determination of vanadium(IV) and vanadium(V) by flow injection analysis using kinetic spectrophotometry with Xylenol Orange.

    Science.gov (United States)

    Oguma, Koichi; Yoshioka, Osamu; Noro, Junji; Sakurai, Hiroki

    2012-07-15

    A flow injection method of analysis has been developed for the simultaneous determination of V(IV) and V(V) using the difference in the rate of complex formation between vanadium in two different oxidation states and Xylenol Orange in acidic media. The proposed method used a spectrophotometric detector equipped with two flow cells aligned with the same optical path to yield two successive peaks per each sample injection. V(IV) and V(V) were determined by solving simultaneous equations in two unknowns, the concentrations of V(IV) and V(V), obtained from measurements of the two peak heights. The detection limit calculated as 3σ of noise signals was 0.01μg/mL for both V(IV) and V(V). The relative standard deviations for V(IV) and V(V) at the 1μg/mL level were 1.6 and 2.4%, respectively. The sample throughput was found to be about 19h(-1). The proposed method was successfully applied to the simultaneous determination of V(IV) and V(V) in synthetic scrubbing solutions used in desulphurization with reasonable accuracy.

  6. Determination of lead in wine and rum samples by flow injection-hydride generation-atomic absorption spectrometry.

    Science.gov (United States)

    Elçi, Latif; Arslan, Zikri; Tyson, Julian F

    2009-03-15

    A method for direct determination of lead in wine and rum samples was developed, using a flow injection hydride generation system coupled to an atomic absorption spectrometer with flame-quartz atomizer (FI-HG-AAS). Lead hyride (PbH(4)) was generated using potassium ferricyanide (K(3)Fe(CN)(6)), as oxidant and sodium tetrahydroborate (NaBH(4)) as reductant. Samples were acidified to 0.40% (v/v) HCl for wine and to 0.30% (v/v) HCl for rum, which were then mixed on-line with 3% (m/v) K(3)Fe(CN)(6) solution in 0.03% (v/v) HCl prior to reaction with 0.2% (m/v) alkaline NaBH(4) solution. Lead contents of a rum and two different red wine samples were determined by FI-HG-AAS agreed with those obtained by ICP-MS. The analytical figures of merit of method developed were determined. The calibration curve was linear up to 8.0 microg L(-1) Pb with a regression coefficient of 0.998. The relative error was lower than 4.58%. The relative standard deviation (n=7) was better than 12%. A detection limit of 0.16 microg L(-1) was achieved for a sample volume of 170 microL.

  7. Assembling Amperometric Biosensors for Clinical Diagnostics

    Directory of Open Access Journals (Sweden)

    Claudia Marina Lagier

    2007-02-01

    Full Text Available Clinical diagnosis and disease prevention routinely require the assessment ofspecies determined by chemical analysis. Biosensor technology offers several benefits overconventional diagnostic analysis. They include simplicity of use, specificity for the targetanalyte, speed to arise to a result, capability for continuous monitoring and multiplexing,together with the potentiality of coupling to low-cost, portable instrumentation. This workfocuses on the basic lines of decisions when designing electron-transfer-based biosensorsfor clinical analysis, with emphasis on the strategies currently used to improve the deviceperformance, the present status of amperometric electrodes for biomedicine, and the trendsand challenges envisaged for the near future.

  8. Thin-film amperometric multibiosensor for simultaneous determination of lactate and glucose in wine.

    Science.gov (United States)

    Shkotova, Lyudmyla V; Piechniakova, Nataliia Y; Kukla, Oleksandr L; Dzyadevych, Sergei V

    2016-04-15

    An amperometric multi-biosensor based on lactate and glucose oxidases has been developed for determination of lactate and glucose in wine. Gold thin-film amperometric electrodes were used as multi-transducers. Analytical characteristics of the multi-biosensor developed were studied. The minimum detectable concentration was 5×10(-6) mol/l for both glucose and lactate. High reproducibility and storage stability of the multi-biosensor are demonstrated in this paper. Lactate and glucose were determined in wine, and a good correlation was obtained with concentrations determined using high-performance liquid chromatography (correlation coefficient for glucose R(2)=0.998, for lactate R(2)=0.718).

  9. Pulsed Amperometry for Anti-fouling of Boron-doped Diamond in Electroanalysis of β-Agonists: Application to Flow Injection for Pharmaceutical Analysis

    Directory of Open Access Journals (Sweden)

    Duangjai Nacapricha

    2006-01-01

    Full Text Available This work presents the construction and application of boron-doped diamond(BDD thin film electrode as sensor for the determination of three β-agonists, viz.salbutamol, terbutaline and clenbuterol. Although well-known as a chemically inertmaterial, BDD film however shows fouling in detection of these compounds using fixedpotentialmode amperometry. A suitable waveform for pulsed amperometric detection(PAD was developed and used to determine the agonist compounds. It was seen that thedeveloped PAD significantly refreshed the BDD surface for long-term detection in flowinjection analysis. Linear working ranges were 0.5-100 μM, 1.0-100 μM and 0.5-50 μM forsalbutamol, terbutaline and clenbuterol, respectively. The developed PAD-BDD system wasapplied to successfully determine salbutamol and terbutaline in commercial pharmaceuticalproducts. The methods were validated with a capillary electrophoresis method.

  10. Fluorescence method using on-line sodium cholate coacervate surfactant mediated extraction for the flow injections analysis of Rhodamine B.

    Science.gov (United States)

    Acosta, Gimena; Talio, María C; Luconi, Marta O; Hinze, Willie L; Fernández, Liliana P

    2014-11-01

    An on-line surfactant mediated extraction method in a flow injection analysis format with fluorescence detection was developed for the determination of Rhodamine B (RhB) in food condiments. The sample was extracted using the phase separation behavior exhibited by the bile salt surfactant, sodium cholate (NaC), upon addition of sodium dodecylsulfate (SDS) in the presence of acid at room temperature. The RhB in the sample was incorporated into the NaC/SDS coacervate phase which was then collected on a glass-wool packed mini column from which it was subsequently eluted using a 1.00 mol L(-1) HCl solution. The inherent fluorescence (λex=555 nm; λem=575 nm) of RhB was employed for detection. Good linearity (r(2)=0.9933) was obtained over the concentration range 0.4-4794-479.0 µg L(-1) RhB. The detection (LOD) and quantification (LOQ) limits were 0.12 and 0.40 µg L(-1), respectively. The method was successfully applied for analysis of RhB in food condiments and spiked samples. The average recoveries ranged from 95.3% to 118.9% at spiked concentration levels of 1.19 and 2.39 µg L(-1). Under optimized conditions, a throughput of 50 samples per hour was achieved. The proposed method may be a valuable tool not only for quality control of food condiments and similar food confectioneries but for the analysis of a variety of other RhB-containing samples as well.

  11. Quantitative Analysis of Piroxicam Using Temperature-Controlled Ionic Liquid Dispersive Liquid Phase Microextraction Followed By Stopped-Flow Injection Spectrofluorimetry

    Directory of Open Access Journals (Sweden)

    Mohammad Reza Ganjali

    2013-07-01

    Full Text Available Background:Piroxicam (PXM belongs to the wide class of non-steroidal anti-inflammatory drugs (NSAIDs. PXM has been widely applied in the treatment of rheumatoid arthritis, gonarthrosis, osteoarthritis, backaches, neuralgia, mialgia. In the presented work, a green and benign sample pretreatment method called temperature-controlled ionic liquid dispersive liquid phase microextraction (TCIL-DLPME was followed with stopped-flow injection spectrofluorimetry (SFIS for quantitation of PXM in pharmaceutical formulations and biological samples.Methods:Temperature-controlled ionic liquid dispersive liquid phase microextraction (TCIL-DLPME was applied as an environmentally friendly sample enrichment method to extract and isolate PXM prior to quantitation. Dispersion of 1-hexyl-3-methylimidazolium hexafluorophosphate ([Hmim][PF6] ionic liquid (IL through the sample aqueous solution was performed by applying a relatively high temperature. PXM was extracted into the extractor, and after phase separation, PXM in the final solution was determined by stopped-flow injection spectrofluorimetry (SFIS.Results and Major Conclusion:Different factors affecting the designed method such as IL amount, diluting agent, pH and temperature were investigated in details and optimized. The method provided a linear dynamic range of 0.2-150 μg l-1, a limit of detection (LOD of 0.046 μg l-1 and a relative standard deviation (RSD of 3.1%. Furthermore, in order to demonstrate the analytical applicability of the recommended method, it was applied for quantitation of PXM in real samples.

  12. A simple and rapid flow-injection chemiluminescence method for the determination of noscapine with Ru(phen)3(2+)-Ce(IV) system.

    Science.gov (United States)

    Rezaei, Behzad; Mokhtari, Ali; Khayamian, Taghi

    2007-08-01

    A new flow injection chemiluminescence (CL) system was used for the determination of noscapine. This technique is based on the reduction effect of noscapine on the Ru(phen)3(3+), which is produced by reaction between Ru(phen)3(2+) and acidic Ce(IV) solutions, and this rapid reduction produces strong CL. Calibration plots were linear over the range of 3.0 x 10(-7) - 2.0 x 10(-6) mol L(-1) and 2.0 x 10(-6) - 2.0 x 10(-4) mol L(-1). The CL intensity was so high, that it is able to produce a detection limit of 6.6 x 10(-8) M noscapine (3sigma). The relative standard deviation of 2.0 x 10(-6) M noscapine was 1.0% (n=10). The proposed method was successfully applied for the flow injection determination of noscapine in cough and Tonin syrup samples. The results of real sample analyses show good recovery percentages (97.3-102.4%). The minimum sampling rate was 100 samples per hour.

  13. Flow injection analysis simulations and diffusion coefficient determination by stochastic and deterministic optimization methods

    Energy Technology Data Exchange (ETDEWEB)

    Kucza, Witold, E-mail: witek@agh.edu.pl

    2013-07-25

    Graphical abstract: -- Highlights: •Former random walk approach for FIA simulations has been improved. •Random walk and uniform dispersion models have been used for FIA simulations. •Diffusivities have been optimized by genetic and the Levenberg–Marquardt methods. •Both approaches have given similar results in agreement with experimental ones. -- Abstract: Stochastic and deterministic simulations of dispersion in cylindrical channels on the Poiseuille flow have been presented. The random walk (stochastic) and the uniform dispersion (deterministic) models have been used for computations of flow injection analysis responses. These methods coupled with the genetic algorithm and the Levenberg–Marquardt optimization methods, respectively, have been applied for determination of diffusion coefficients. The diffusion coefficients of fluorescein sodium, potassium hexacyanoferrate and potassium dichromate have been determined by means of the presented methods and FIA responses that are available in literature. The best-fit results agree with each other and with experimental data thus validating both presented approaches.

  14. Preprocessing, classification modeling and feature selection using flow injection electrospray mass spectrometry metabolite fingerprint data.

    Science.gov (United States)

    Enot, David P; Lin, Wanchang; Beckmann, Manfred; Parker, David; Overy, David P; Draper, John

    2008-01-01

    Metabolome analysis by flow injection electrospray mass spectrometry (FIE-MS) fingerprinting generates measurements relating to large numbers of m/z signals. Such data sets often exhibit high variance with a paucity of replicates, thus providing a challenge for data mining. We describe data preprocessing and modeling methods that have proved reliable in projects involving samples from a range of organisms. The protocols interact with software resources specifically for metabolomics provided in a Web-accessible data analysis package FIEmspro (http://users.aber.ac.uk/jhd) written in the R environment and requiring a moderate knowledge of R command-line usage. Specific emphasis is placed on describing the outcome of modeling experiments using FIE-MS data that require further preprocessing to improve quality. The salient features of both poor and robust (i.e., highly generalizable) multivariate models are outlined together with advice on validating classifiers and avoiding false discovery when seeking explanatory variables.

  15. Comparison of Uric Acid Quantity with Different Food in Human Urine by Flow Injection Chemiluminescence Analysis

    Directory of Open Access Journals (Sweden)

    Jiajia Wang

    2013-01-01

    Full Text Available Based on the inhibitory effect of uric acid (UA on luminol-Co2+ chemiluminescence (CL system, a sensitive method for the determination of UA at nanomolar level by flow injection (FI CL was proposed. The proposed method was successfully applied to real-time monitoring of UA excretion in human 24 h urine with different food intake, showing that meats, vegetables, and porridge intake caused differential UA excretions of 879, 798, and 742 mg, respectively. It was also found that UA concentrations in urine under the three kinds of food intake simultaneously reached maximum at 2 h after meals with the values of 417, 318, and 288 μg mL−1, respectively. The UA concentration in human serum was also determined by this approach, and the possible mechanism of luminol-Co2+-UA CL reaction was discussed in detail.

  16. Irreversibility analysis of magneto-hydrodynamic nanofluid flow injected through a rotary disk

    Directory of Open Access Journals (Sweden)

    Rashidi Mohammad Mehdi

    2015-01-01

    Full Text Available The non-linear Navier-Stokes equations governed on the nanofluid flow injected through a rotary porous disk in the presence of an external uniform vertical magnetic field can be changed to a system of non-linear partial differential equations by applying similar parameter. In this study, partial differential equations are analytically solved by the modified differential transform method, Pade differential transformation method to obtain self-similar functions of motion and temperature. A very good agreement is observed between the obtained results of Pade differential transformation method and those of previously published ones. Then it has become possible to do a comprehensive parametric analysis on the entropy generation in this case to demonstrate the effects of physical flow parameters such as magnetic interaction parameter, injection parameter, nanoparticle volume fraction, dimensionless temperature difference, rotational Brinkman number and the type of nanofluid on the problem.

  17. Espectrofotometria de zinco em fertilizantes em fluxo Flow injection spectrophotometry of zinc in mineral fertilizers

    Directory of Open Access Journals (Sweden)

    Arnaldo Antonio Rodella

    1999-07-01

    Full Text Available Um sistema de análise química por injeção em fluxo é proposto para a determinação espectrofotométrica de zinco em amostras de misturas de fertilizantes minerais, empregando-se zincon como reagente cromogênico. O procedimento analítico envolve redução de íons metálicos por ácido ascórbico, complexação com íon cianeto, seguindo-se a descomplexação seletiva do zinco com formaldeído, liberando-o para que reaja com o zincon formando um complexo azul. A aplicação do método proposto à extratos de mistura de fertilizantes indicou que a ação de interferentes pode ser contornada e que resultados comparáveis aos da espectrometria de absorção atômica são obtidos.A flow injection system for zinc analysis in mineral fertilizer mixtures is proposed using zincon as chromogenic reagent. The effect of interfering ions such as Cu2+, Fe3+, Mn2+ was eliminated by reduction (using ascorbic acid and complexation of these metal íons with cyanide, with zinc included. Zinc is allowed to react with zincon only after the destruction of the zinc cyano complex with formaldehyde. Flow injection analysis permitted efficient control of the reaction time so that only the zinc ion is set free to produce a blue complex with zincon. Zinc was determined in 16 fertilizer mixtures (3 replicates with precision and accuracy comparable to atomic absorption spectrometry.

  18. Use of flow injection mass spectrometric fingerprinting and chemometrics for differentiation of three black cohosh species

    Energy Technology Data Exchange (ETDEWEB)

    Huang, Huilian [Food Composition and Methods Development Laboratory, Beltsville Human Nutrition Research Center, Agricultural Research Service, U.S. Department of Agriculture, Beltsville, MD (United States); Key Laboratory of Modern Preparation of TCM, Jiangxi University of Traditional Chinese Medicine, Ministry of Education, Nanchang, Jiangxi Province (China); Sun, Jianghao [Food Composition and Methods Development Laboratory, Beltsville Human Nutrition Research Center, Agricultural Research Service, U.S. Department of Agriculture, Beltsville, MD (United States); McCoy, Joe-Ann [The North Carolina Arboretum Germplasm Repository, UNC Affiliate Campus, Asheville, NC (United States); Zhong, Haiyan [College of Food Science and Engineering, Central South University of Forestry and Technology, Changsha, Hunan Province (China); Fletcher, Edward J. [Strategic Sourcing, Inc., Banner Elk, NC 28604 (United States); Harnly, James, E-mail: harnly.james@ars.usda.gov [Food Composition and Methods Development Laboratory, Beltsville Human Nutrition Research Center, Agricultural Research Service, U.S. Department of Agriculture, Beltsville, MD (United States); Chen, Pei, E-mail: pei.chen@ars.usda.gov [Food Composition and Methods Development Laboratory, Beltsville Human Nutrition Research Center, Agricultural Research Service, U.S. Department of Agriculture, Beltsville, MD (United States)

    2015-03-01

    Flow injection mass spectrometry (FIMS) was used to provide chemical fingerprints of black cohosh (Actaea racemosa L.) in a manner of minutes by omitting the separation step. This method has proven to be a powerful tool for botanical authentication and in this study it was used to distinguish between three Actaea species prior to a more detailed chemical analysis using ultra high-performance liquid chromatography high-resolution mass spectrometry (UHPLC–HRMS). Black cohosh has become increasingly popular as a dietary supplement in the United States for the treatment of symptoms related to menopause. However, it has been known to be adulterated with the Asian Actaea dahurica (Turcz. ex Fisch. & C.A.Mey.) Franch. species (syn. Cimicifuga dahurica (Turcz.) Maxim). Existing methods for identification of black cohosh and differentiation of Actaea species are usually lengthy, laborious, and lack robustness, often based on the comparison of a few pre-selected components. Chemical fingerprints were obtained for 77 black cohosh samples and their related species using FIMS in the negative ion mode. The analysis time for each sample was less than 2 min. All data were processed using principal component analysis (PCA). FIMS fingerprints could readily differentiate all three species. Representative samples from each of the three species were further examined using UHPLC–MS to provide detailed profiles of the chemical differences between the three species and were compared to the PCA loadings. This study demonstrates a simple, fast, and easy analytical method that can be used to differentiate A. racemosa, Actaea podocarpa, and A. dahurica. - Highlights: • Flow injection mass spectrometry (FIMS) was used to provide chemical fingerprints of black cohosh (Actaea racemosa L.) in a manner of minutes by omitting the separation step. • FIMS can discriminate between A. dahurica, A. podocarpa, and A. racemosa. • FIMS is a valuable screening tool for authentication of botanicals.

  19. Flow injection online spectrophotometric determination of uranium after preconcentration on XAD-4 resin impregnated with nalidixic acid.

    Science.gov (United States)

    Shahida, Shabnam; Ali, Akbar; Khan, Muhammad Haleem; Saeed, Muhammad Mufazzal

    2013-02-01

    In this work, spectrophotometer was used as a detector for the determination of uranium from water, biological, and ore samples with a flow injection system coupled with solid phase extraction. In order to promote the online preconcentration of uranium, a minicolumn packed with XAD-4 resin impregnated with nalidixic acid was utilized. The system operation was based on U(VI) ion retention at pH 6 in the minicolumn at flow rate of 15.2 mL min(-1). The uranium complex was removed from the resin by 0.1 mol dm(-3) HCl at flow rate of 3.2 mL min(-1) and was mixed with arsenazo III solution (0.05 % solution in 0.1 mol dm(-3) HCl, 3.2 mL min(-1)) and driven to flow through cell of spectrophotometer where its absorbance was measured at 651 nm. The influence of chemical (pH and HCl (as eluent and reagent medium) concentration) and flow (sample and eluent flow rate and preconcentration time) parameters that could affect the performance of the system as well as the possible interferents was investigated. At the optimum conditions for 60 s preconcentration time (15.2 mL of sample volume), the method presented a detection limit of 1.1 μg L(-1), a relative standard deviation (RSD) of 0.8 % at 100 μg L(-1), enrichment factor of 30, and a sample throughput of 42 h(-1), whereas for 300 s of the preconcentration time (76 mL of sample volume), a detection limit of 0.22 μg L(-1), a RSD of 1.32 % at 10 μg L(-1), enrichment factor of 150, and a sampling frequency of 11 h(-1) were reported.

  20. Critical evaluation of acetylthiocholine iodide and acetylthiocholine chloride as substrates for amperometric biosensors based on acetylcholinesterase.

    Science.gov (United States)

    Bucur, Madalina-Petruta; Bucur, Bogdan; Radu, Gabriel-Lucian

    2013-01-25

    Numerous amperometric biosensors have been developed for the fast analysis of neurotoxic insecticides based on inhibition of cholinesterase (AChE). The analytical signal is quantified by the oxidation of the thiocholine that is produced enzymatically by the hydrolysis of the acetylthiocholine pseudosubstrate. The pseudosubstrate is a cation and it is associated with chloride or iodide as corresponding anion to form a salt. The iodide salt is cheaper, but it is electrochemically active and consequently more difficult to use in electrochemical analytical devices. We investigate the possibility of using acetylthiocholine iodide as pseudosubstrate for amperometric detection. Our investigation demonstrates that operational conditions for any amperometric biosensor that use acetylthiocholine iodide must be thoroughly optimized to avoid false analytical signals or a reduced sensitivity. The working overpotential determined for different screen-printed electrodes was: carbon-nanotubes (360 mV), platinum (560 mV), gold (370 mV, based on a catalytic effect of iodide) or cobalt phthalocyanine (110 mV, but with a significant reduced sensitivity in the presence of iodide anions).

  1. Flow injection chemiluminescence immunoassay of microcystin-LR by using PEI-modified magnetic beads as capturer and HRP-functionalized silica nanoparticles as signal amplifier.

    Science.gov (United States)

    Lu, Jusheng; Wei, Wei; Yin, Lihong; Pu, Yuepu; Liu, Songqin

    2013-03-07

    A rapid sandwiched immunoassay of microcystin-LR (MC-LR) in water is proposed with flow injection chemiluminescence detection. The magnetic beads (MBs) were first modified with polyethyleneimine (PEI) by acylamide bond between the carboxyl group on the surface of MBs and the primary amine group in PEI, followed by immobilizing of anti-MC-LR (Ab1) onto PEI with glutaraldehyde as linkage. The resulting Ab1 modified MBs captured the target MC-LR in water, reacted with the horseradish peroxidase and anti-MC-LR co-immobilized silica nanoparticles, and were detected with flow injection chemiluminescence. When using PEI/MBs as the carrier of anti-MC-LR, the CL signal was greatly enhanced up to 9-fold compared to that using MBs without PEI modification. The CL signal was further amplified 13-fold when Si/Ab2 was used as the signal probe. Under the optimal conditions, the present immunoassay exhibited a wide quantitative range from 0.02 to 200 μg L(-1) with a detection limit of 0.006 μg L(-1), which was much lower than the WHO provisional guideline limit of 1.0 μg L(-1) for MC-LR in drinking water. The relative standard deviation was 4.8% and the recoveries for the spiked samples ranged from 84% to 115%, which indicated acceptable precision and accuracy for MC-LR. The present method is easier to perform and less time-consuming (the entire analysis process lasted about 40 minutes) and has been applied to the detection of MC-LR in different water samples successfully.

  2. Amperometric sensing in the gas-phase

    Energy Technology Data Exchange (ETDEWEB)

    Knake, Rene [University of Basel, Department of Chemistry, Spitalstrasse 51, 4004 Basel (Switzerland); Jacquinot, Patrick [University of Basel, Department of Chemistry, Spitalstrasse 51, 4004 Basel (Switzerland); Hodgson, Alexia W.E. [University of Basel, Department of Chemistry, Spitalstrasse 51, 4004 Basel (Switzerland); Hauser, Peter C. [University of Basel, Department of Chemistry, Spitalstrasse 51, 4004 Basel (Switzerland)]. E-mail: peter.hauser@unibas.ch

    2005-09-06

    The design of amperometric sensors for gaseous species presents a challenge as the gas phase has to be brought into contact with a solid electrode as well as an electrolyte phase which usually is liquid. However, many species of analytical interest are electroactive, such as SO{sub 2}, NO {sub x}, O{sub 3}, CO, formaldehyde or ethanol, and electrochemical means are always attractive in designing sensors because the electronic signal is obtained directly. Therefore, different approaches have been implemented and some types of such sensors have been available commercially for quite some time. Nevertheless, many new developments with regard to an improvement of sensitivity, selectivity and in the construction of these devices have been reported over the last few years, as well as approaches to miniaturization. In this review it is attempted to give an overview of the state of the art of this field, highlighting recent developments.

  3. Flow injection analysis with on-line nylon powder extraction for room-temperature phosphorescence determination of thiabendazole.

    Science.gov (United States)

    Piccirilli, G N; Escandar, G M

    2009-07-30

    A fast and very selective flow-through phosphorescence optosensor was designed and characterized for the determination of the fungicide thiabendazole in water samples. For the first time, thiabendazole was determined using a flow-through optosensor based on the phosphorescence signals obtained when it is retained in a solid support. While thiabendazole does not phosphoresce in packing materials commonly used to fill the flow-cell, significant emission signals are observed when it is retained on nylon powder in the presence of iodide and sulfite. The experimental set-up was based on a flow-injection manifold coupled to an on-line phosphorescence detector containing nylon powder packed in a conventional flow-cell. Potassium iodide and sodium sulfite were added to sample aliquots to improve the thiabendazole phosphorescence and injected in the flow manifold using water as carrier. After the phosphorescence emission was registered, the analyte was eluted from the packed nylon with a 65% (v/v) methanol-water mixture. Optimal instrumentation, experimental and flow conditions were evaluated. Using a sample volume of 2000 microL, the analytical signal showed a very good linearity in the range 12.9-110 ng mL(-1), with a detection limit of 4.5 ng mL(-1), and a sample throughput of about 14 samples per hour. The effects of the presence of concomitant species in the thiabendazole phosphorescence signal were studied, and a comparison with the fluorescence nylon-powder optosensor was carried out and discussed. Finally, the applicability of the proposed optosensor was tested in water samples, and satisfactory recoveries ranging between 97% and 105% were obtained.

  4. Determination of trace metals in seawater by an automated flow injection ion chromatograph pretreatment system with ICPMS.

    Science.gov (United States)

    Ho, Tung-Yuan; Chien, Chia-Te; Wang, Bing-Nan; Siriraks, Archava

    2010-09-15

    A novel flow injection ion chromatograph (FI-IC) system has been developed to fully automate pretreatment procedures for multi-elemental analysis of trace metals in seawater by inductively coupled plasma mass spectrometer (ICPMS). By combining 10-port, 2 position and 3-way valves in the FI-IC manifold, the system effectively increase sample throughput by simultaneously processing three seawater samples online for: sample loading, injection, buffering, preconcentration, matrix removal, metal elution, and sample collection. Forty-two seawater samples can be continuously processed without any manual handing. Each sample pretreatment takes about 10 min by consuming 25 mL of seawater and producing 5 mL of processed concentrated samples for multi-elemental offline analysis by ICPMS. The offline analysis improve analytical precision and significantly increase total numbers of isotopes determined by ICPMS, which include the metals Al, Cd, Co, Cr, Cu, Fe, Mn, Ni, Pb, Ti, V, and Zn. The blank value and detection limits of trace metals using the system with ICPMS analysis all range from 0.1 to 10 parts per trillion (ppt), except Al, Fe, and Zn. The accuracy of the pretreatment system was validated by measuring open-ocean and coastal reference seawater, NASS-5 and CASS-4. Using the system with ICPMS analysis, we have obtained reliable trace metal concentrations in the water columns of the South China Sea. Possessing the features of full automation, high throughput, low blank, and low reagent volume used, the system automates and simplifies rigorous and complicated pretreatment procedures for multi-elemental analysis of trace metals in seawater and effectively enhances analytical capacity for trace metal analysis in environmental and seawater samples.

  5. Ion-selective electrodes for potentiometric determination of ranitidine hydrochloride, applying batch and flow injection analysis techniques.

    Science.gov (United States)

    Issa, Yousry M; Badawy, Sayed S; Mutair, Ali A

    2005-12-01

    New ranitidine hydrochloride (RaCl)-selective electrodes of the conventional polymer membrane type are described. They are based on incorporation of ranitidine-tetraphenylborate (Ra-TPB) ion-pair or ranitidine-phosphotungstate (RaPT) ion-associate in a poly(vinyl chloride) (PVC) membrane plasticized with dioctylphthalate (DOP) or dibutylphthalate (DBP). The electrodes are fully characterized in terms of the membrane composition, solution temperature, and pH. The sensors showed fast and stable responses. Nernstian response was found over the concentration range of 2.0 x 10(-5) M to 1.0 x 10(-2) M and 1.0 x 10(-5) M to 1.0 x 10(-2) M in the case of Ra-TPB electrode and over the range of 1.03 x 10(-5) M to 1.00 x 10(-2) M and 1.0 x 10(-5) M to 1.0 x 10(-2) M in the case of Ra-PT electrode for batch and FIA systems, respectively. The electrodes exhibit good selectivity for RaCl with respect to a large number of common ions, sugars, amino acids, and components other than ranitidine hydrochloride of the investigated mixed drugs. The electrodes have been applied to the potentiometric determination of RaCl in pure solutions and in pharmaceutical preparations under batch and flow injection conditions with a lower detection limit of 1.26 x 10(-5) M and 5.62 x 10(-6) M at 25 +/- 1 degrees C. An average recovery of 100.91% and 100.42% with a relative standard deviation of 0.72% and 0.53% has been achieved.

  6. Simultaneous flow injection preconcentration of lead and cadmium using cloud point extraction and determination by atomic absorption spectrometry

    Energy Technology Data Exchange (ETDEWEB)

    Silva, Edson Luiz [Centro de Energia Nuclear na Agricultura, Universidade de Sao Paulo, Av. Centenario, 303, CP 96, 13416-000 Piracicaba, SP (Brazil)], E-mail: edsonqmc@hotmail.com; Santos Roldan, Paulo dos [Centro de Energia Nuclear na Agricultura, Universidade de Sao Paulo, Av. Centenario, 303, CP 96, 13416-000 Piracicaba, SP (Brazil)

    2009-01-15

    A flow injection (FI) micelle-mediated separation/preconcentration procedure for the determination of lead and cadmium by flame atomic absorption spectrometry (FAAS) has been proposed. The analytes reacted with 1-(2-thiazolylazo)-2-naphthol (TAN) to form hydrophobic chelates, which were extracted into the micelles of 0.05% (w/v) Triton X-114 in a solution buffered at pH 8.4. In the preconcentration stage, the micellar solution was continuously injected into a flow system with four mini-columns packed with cotton, glass wool, or TNT compresses for phase separation. The analytes-containing micelles were eluted from the mini-columns by a stream of 3 mol L{sup -1} HCl solution and the analytes were determined by FAAS. Chemical and flow variables affecting the preconcentration of the analytes were studied. For 15 mL of preconcentrated solution, the enhancement factors varied between 15.1 and 20.3, the limits of detection were approximately 4.5 and 0.75 {mu}g L{sup -1} for lead and cadmium, respectively. For a solution containing 100 and 10 {mu}g L{sup -1} of lead and cadmium, respectively, the R.S.D. values varied from 1.6 to 3.2% (n = 7). The accuracy of the preconcentration system was evaluated by recovery measurements on spiked water samples. The method was susceptible to matrix effects, but these interferences were minimized by adding barium ions as masking agent in the sample solutions, and recoveries from spiked sample varied in the range of 95.1-107.3%.

  7. Band-type microelectrodes for amperometric immunoassays

    Energy Technology Data Exchange (ETDEWEB)

    Lee, Ga-Yeon; Chang, Young Wook; Ko, Hyuk [Department of Materials Science and Engineering, Yonsei University, 134 Shinchon-dong, Seodaemun-gu, Seoul, 120-749 (Korea, Republic of); Kang, Min-Jung [Korea Institute of Science and Technology (KIST), Seoul (Korea, Republic of); Pyun, Jae-Chul, E-mail: jcpyun@yonsei.ac.kr [Department of Materials Science and Engineering, Yonsei University, 134 Shinchon-dong, Seodaemun-gu, Seoul, 120-749 (Korea, Republic of)

    2016-07-20

    A band-type microelectrode was made using a parylene-N film as a passivation layer. A circular-type, mm-scale electrode with the same diameter as the band-type microelectrode was also made with an electrode area that was 5000 times larger than the band-type microelectrode. By comparing the amperometric signals of 3,5,3′,5′-tetramethylbenzidine (TMB) samples at different optical density (OD) values, the band-type microelectrode was determined to be 9 times more sensitive than the circular-type electrode. The properties of the circular-type and the band-type electrodes (e.g., the shape of their cyclic voltammograms, the type of diffusion layer used, and the diffusion layer thickness per unit electrode area) were characterized according to their electrode area using the COMSOL Multiphysics software. From these simulations, the band-type electrode was estimated to have the conventional microelectrode properties, even when the electrode area was 100 times larger than a conventional circular-type electrode. These results show that both the geometry and the area of an electrode can influence the properties of the electrode. Finally, amperometric analysis based on a band-type electrode was applied to commercial ELISA kits to analyze human hepatitis B surface antigen (hHBsAg) and human immunodeficiency virus (HIV) antibodies. - Highlights: • A band-type microelectrode was made using a parylene-N film as a passivation layer. • The band-type microelectrode was 14-times more sensitive than circular-type electrode. • The influence of geometry on microelectrode properties was simulated using COMSOL. • The band-type electrode was applied to ELISA kits for hHBsAg and hHIV-antibodies.

  8. Determination of Hypochlorite in Bleaching Products with Flower Extracts to Demonstrate the Principles of Flow Injection Analysis

    Science.gov (United States)

    Ramos, Luiz Antonio; Prieto, Katia Roberta; Carvalheiro, Eder Tadeu Gomes; Carvalheiro, Carla Cristina Schmitt

    2005-01-01

    The use of crude flower extracts to the principle of analytical chemistry automation, with the flow injection analysis (FIA) procedure developed to determine hypochlorite in household bleaching products was performed. The FIA comprises a group of techniques based on injection of a liquid sample into a moving, nonsegmented carrier stream of a…

  9. Introduction of Hydrogen Peroxide as an Oxidant in Flow Injection Analysis: Speciation of Cr(III) and Cr(VI)

    DEFF Research Database (Denmark)

    Andersen, Jens Enevold Thaulov

    1998-01-01

    Hydrogen peroxide was used as an oxidant in Flow Injection Analysis (FIA). The formation of gaseous components during the analysis was suppressed by maintaining a concentration lower than 0.15% of hydrogen peroxide in 0.1 M NaOH. By this method Cr(III) was oxidised on-line to Cr(VI) which...

  10. Comparison of Flow Injection MS, NMR, and DNA Sequencing: Methods for Identification and Authentication of Black Cohosh (Actaea racemosa)

    Science.gov (United States)

    Flow injection mass spectrometry (FIMS) and proton nuclear magnetic resonance spectrometry (1H-NMR), two metabolic fingerprinting methods, and DNA sequencing were used to identify and authenticate Actaea species. Initially, samples of Actaea racemosa L. from a single source were distinguished from ...

  11. Trends and perspectives of flow injection/sequential injection on-line sample-pretreatment schemes coupled to ETAAS

    DEFF Research Database (Denmark)

    Wang, Jianhua; Hansen, Elo Harald

    2005-01-01

    Flow injection (FI) analysis, the first generation of this technique, became in the 1990s supplemented by its second generation, sequential injection (SI), and most recently by the third generation (i.e.,Lab-on-Valve). The dominant role played by FI in automatic, on-line, sample pretreatments...

  12. How Flow Injection Analysis (FIA) over the past 25 years has changed our way of performing chemical analyses

    DEFF Research Database (Denmark)

    Hansen, Elo Harald; Miró, Manuel

    2007-01-01

    Briefly looking back on the impact of flow injection analysis (FIA), as reflected in the rapid growth of publications in the scientific literature, and touching upon many of the novel and unique analytical chemical possibilities that FIA and its sequels, sequential injection analysis (SIA) and Lab-on-Valve...

  13. Determination of free and total myo-inositol in infant formula and adult/pediatric nutritional formula by high- performance anion exchange chromatography with pulsed amperometric detection, including a novel total extraction using microwave-assisted acid hydrolysis and enzymatic treatment: first action 2012.12.

    Science.gov (United States)

    Ellingson, David; Pritchard, Ted; Foy, Pamela; King, Kathryn; Mitchell, Barbara; Austad, John; Winters, Doug; Sullivan, Darryl; Dowell, Dawn

    2013-01-01

    After an assessment of data generated from a single-laboratory validation study published in J. AOAC Int. 95, 1469-1478 (2012), a method for determining total myo-inositol in infant formula and adult/ pediatric nutritional formula by high-performance anion exchange chromatography with pulsed amperometric detection (HPAEC-PAD), including extraction by using microwave-assisted acid hydrolysis and enzymatic treatment was presented for consideration by AOAC during the AOAC Annual Meeting held in Las Vegas, NV, from September 30 to October 3, 2012. The Expert Review Panel on Infant Formula and Adult Nutritionals concluded that the method met the criteria set by the standard method performance requirements (SMPRs) for the determination of free myo-inositol and approved the method as AOAC Official First Action. The method also determines total myo-inositol, but includes bound sources that the SMPRs exclude. The method involves using HPAEC-PAD for free myo-inositol and a total myo-inositol determination by two different techniques. The first technique uses the conventional acid hydrolysis with 6 h incubation in an autoclave. The second uses a microwave-assisted acid hydrolysis with enzymatic treatment that decreases the extraction time.

  14. Flow-injection Chemiluminescence Sensor for the Determination of Gallic Acid by Immobilizing Luminol and Periodate on Anion-exchange Resin

    Institute of Scientific and Technical Information of China (English)

    ZHANG,Si-Chun(张四纯); ZHOU,Guo-Jun(周国俊); JU,Huang-Xian(鞠熀先)

    2002-01-01

    A novel chemihuminescence (CL) sensor for the determination of gallic acid combined with flow injection analysis was developed by electrostatically immobilizing luminol and periodate on anion-exchange resins respectively. Gallic acid was sensed by its enhancing effect on the weak CL reaction between luminol and periodate, which were eluted from the ion exchang ecolumn.The possible reaction mechanism of the CL system was suggested and discussed. The response of the sensor to gallic acid concentration was linear over the range of 8.0 × 10-9-1.0 × 10-6 mol/L with a detection limit of 6.5 × 10-9 mol/L (3σσ). The relative standard deviation (RSD) for 7 repetitive determinations of gallic acid (1.0 × 10-7 moL/L) was 1.8%. The sensor could be used for over 400 times determination with a good reproducibility.

  15. Development of an automatic method for americium and plutonium separation and preconcentration using an multisyringe flow injection analysis-multipumping flow system.

    Science.gov (United States)

    Fajardo, Yamila; Ferrer, Laura; Gómez, Enrique; Garcias, Francesca; Casas, Monserrat; Cerdà, Víctor

    2008-01-01

    A new procedure for automatic separation and preconcentration of 241Am and 239+240Pu from interfering matrixes using transuranide (TRU)-resin is proposed. Combination of the multisyringe flow injection analysis and multipumping flow system techniques with the TRU-resin allows carrying out the sampling treatment and separation in a short time using large sample volumes. Americium is eluted from the column with 4 mol L(-1) hydrochloric acid, and then plutonium is separated via on-column Pu(IV) reduction to Pu(III) with titanium(III) chloride. The corresponding alpha activities are measured off-line, with a relative standard deviation of 3% and a lower limit of detection of 0.004 Bq mL(-1), by using a multiplanchet low-background proportional counter.

  16. Nonaqueous catalytic fluorometric trace determination of vanadium based on the pyronine B-hydrogen peroxide reaction and flow injection after cloud point extraction.

    Science.gov (United States)

    Paleologos, E K; Koupparis, M A; Karayannis, M I; Veltsistas, P G

    2001-09-15

    The catalytic effect of vanadium on the pyronine B-H2O2 system is examined. Enhancement of the catalytic reaction rate along with the efficiency and selectivity against vanadium is achieved in a formic acid environment in the presence of a nonionic surfactant (Triton X-114). Elimination of drastic interference caused by inorganic acids and aqueous matrix along with a 50-fold preconcentration of vanadium are facilitated through cloud point extraction of its neutral complex with 8-quinolinol in an acidic solution. Subsequent flow injection analysis (FIA) with fluorometric detection renders the proposed method ideal for selective and cost-effective determination of as little as 0.020 microng L(-1) vanadium in environmental, biological, and food substrates. The preconcentration step can be applied simultaneously to multiple samples, allowing for massive preparation prior to analysis, compensating, thus, for the time-consuming procedure.

  17. Determination of total iron in food samples after flow injection preconcentration on polyurethane foam functionalized with N,N-bis(salicylidene)-1,3-propanediamine.

    Science.gov (United States)

    Abdel-Azeem, S M; Bader, N R; Kuss, H M; El-Shahat, M F

    2013-06-01

    A highly selective flow injection sorption system was developed for the fast determination of total iron in food samples. Iron (III) was reduced to iron (II) by ascorbic acid and preconcentrated on a mini-column packed with polyurethane foam (PUF) functionalized with N,N-bis(salicylidene)-1,3-propanediamine (SPDA). The retained Fe (II) was eluted with hydrochloric acid and subsequently reacted to 2,4,6-tri(2'-pyridyl)-1,3,5-triazine (TPTZ) then measured at 593 nm. The procedure has resulted preconcentration factor 36, sample frequency 20 h(-1) and detection limit 18 μg L(-1). The precision (RSD) was found to be 5.7% and 3.1% at concentration levels 0.1 and 5.0 μg mL(-1) iron (II), respectively. Finally, the method was successfully applied to determination of total iron in reference material and food samples.

  18. Dilution Methods in Flow Injection Analysis. Evaluation of Different Approaches as Exemplified for the Determination of Nitrosyl in Concentrated Sulphuric Acid

    DEFF Research Database (Denmark)

    Jørgensen, Ulla Vang; Nielsen, Steffen; Hansen, Elo Harald

    1998-01-01

    Instigated by developing a flow injection procedure for assay of nitrosyl in concentrated sulphuric acid, different approaches for reliable and robust on-line dilution in FIA were evaluated. These comprised the application of mixing tees in conjunction with mixing coils (including knotted reactors...... approach the criteria stipulated were that the procedure should allow a dilution factor of approximately 100, yet without excessive zone spreading, so that it, on one hand, effectively could eliminate the pronounced Schlieren effect encountered when mixing concentrated sulphuric acid with an aqueous...... in conjunction with knotted reactors of relatively large internal diameter (1.5 mm). The optimized FI-manifold was used with the Griess method for the spectrophotometric assay of nitrosyl (nitrite) in standards prepared in the matrix of concentrated sulphuric acid (detection limit 0.16 mg/l NO+-N (3s...

  19. Determination of formaldehyde in frozen fish with formaldehyde dehydrogenase using a flow injection system with an incorporated gel-filtration chromatrography column

    DEFF Research Database (Denmark)

    Bechmann, Iben Ell

    1996-01-01

    in a FIA system. The FIA system is furnished with a gel-filtration chromatography column for on-line removal of the proteins from the extract before the enzymatic analysis is performed. Compared with the standard methods for determination of formaldehyde in fish products the present method is much faster......A flow injection analysis (FIA) system for determination of formaldehyde in frozen fish products is described. The system provides a rapid and selective determination of formaldehyde in aqueous fish extracts by the combination of a deproteinization procedure and a stopped-now enzymatic approach...... and less affected by interferences. The limit of detection for the proposed method is 2.5 mg/l of formaldehyde. The sampling frequency is about 10 determinations per hour....

  20. Characterisation of organic and conventional sweet basil leaves using chromatographic and flow-injection mass spectrometric (FIMS) fingerprints combined with principal component analysis.

    Science.gov (United States)

    Lu, Yingjian; Gao, Boyan; Chen, Pei; Charles, Denys; Yu, Liangli Lucy

    2014-07-01

    Sweet basil, Ocimum basilicum, is one of the most important and wildly used spices and has been shown to have antioxidant, antibacterial, and anti-diarrheal activities. In this study, high performance liquid chromatographic (HPLC) and flow-injection mass spectrometric (FIMS) fingerprinting techniques were used to differentiate organic and conventional sweet basil leaf samples. Principal component analysis (PCA) of the fingerprints indicated that both HPLC and FIMS fingerprints could effectively detect the chemical differences in the organic and conventional sweet basil leaf samples. This study suggested that the organic basil sample contained greater concentrations of almost all the major compounds than its conventional counterpart on a per same botanical weight basis. The FIMS method was able to rapidly differentiate the organic and conventional sweet basil leaf samples (1min analysis time), whereas the HPLC fingerprints provided more information about the chemical composition of the basil samples with a longer analytical time.

  1. Selective Flow Injection Analysis of Ultra-trace Amounts of Cr(VI), Preconcentration of It by Solvent Extraction, and Determination by Electrothermal Atomic Absorption Spectrometry (ETAAS)

    DEFF Research Database (Denmark)

    Nielsen, Steffen; Sturup, Stefan; Spliid, Henrik

    1999-01-01

    A rapid, robust, sensitive and selective time-based flow injection (FI) on-line solvent extraction system interfaced with electrothermal atomic absorption spectrometry (ETAAS) is described for analyzing ultra-trace amounts of Cr(VI). The sample is initially mixed on-line with isobutyl methyl ketone......(VI) was achieved after preconcentration for 99 s at a sample flow rate of 5.5 ml min-1, as compared to direct introduction of 55 mul of sample, yielding a detection limit (3sigma) of 3.3 ng l-1. The sampling frequency was 24.2 samples h-1. The proposed method was successfully evaluated by analyzing a NIST Cr...

  2. Method for (236)U Determination in Seawater Using Flow Injection Extraction Chromatography and Accelerator Mass Spectrometry.

    Science.gov (United States)

    Qiao, Jixin; Hou, Xiaolin; Steier, Peter; Nielsen, Sven; Golser, Robin

    2015-07-21

    An automated analytical method implemented in a flow injection (FI) system was developed for rapid determination of (236)U in 10 L seawater samples. (238)U was used as a chemical yield tracer for the whole procedure, in which extraction chromatography (UTEVA) was exploited to purify uranium, after an effective iron hydroxide coprecipitation. Accelerator mass spectrometry (AMS) was applied for quantifying the (236)U/(238)U ratio, and inductively coupled plasma mass spectrometry (ICPMS) was used to determine the absolute concentration of (238)U; thus, the concentration of (236)U can be calculated. The key experimental parameters affecting the analytical effectiveness were investigated and optimized in order to achieve high chemical yields and simple and rapid analysis as well as low procedure background. Besides, the operational conditions for the target preparation prior to the AMS measurement were optimized, on the basis of studying the coprecipitation behavior of uranium with iron hydroxide. The analytical results indicate that the developed method is simple and robust, providing satisfactory chemical yields (80-100%) and high analysis speed (4 h/sample), which could be an appealing alternative to conventional manual methods for (236)U determination in its tracer application.

  3. Indirect flow-injection spectrophotometric determination of meloxicam, tenoxicam and piroxicam in pharmaceutical formulations.

    Science.gov (United States)

    Al-Momani, Idrees F

    2006-12-01

    A simple and sensitive indirect spectrophotometric method for the assay of meloxicam (MX), tenoxicam (TX) and piroxicam (PX) in pure and in pharmaceutical formulations by flow injection analysis (FIA) has been proposed. The method is based on the oxidation of these drugs by a known excess of N-bromosuccinimide (NBS) in an acidic medium, followed by a reaction of excess oxidant with chloranilic acid (CAA) to bleach its purple color. The absorbance values increased linearly with increasing concentrations of the drugs. Variables, such as the acidity, reagent concentrations, flow rate of reagents and other FI parameters were optimized to produce the most sensitive and reproducible results. The system obeyed Beer's low over concentration ranges of 10 - 160, 20 - 200 and 10 - 160 microg/ml for MX, TX and PX, respectively. The common excipients and additives did not interfere with their determinations. The method was successfully applied to the determinations of MX, TX and PX in various pharmaceutical preparations. The results obtained by the proposed method were found to be in good agreement with those found by the official HPLC methods.

  4. Longitudinal cross sectional mixing images of the pipe flow with periodical branching flow injections

    Science.gov (United States)

    Ueda, Toshihisa; Sunho, You; Higuchi, Naotaka

    2008-11-01

    Effect of periodical injection of branching flows on the mixing in a pipe flow is experimentally investigated. Glycerin is used as a working fluid. The glycerin flows in a steady state condition in the main flow pipe while the branching flow is injected periodically from three pipes equipped normal to the main flow pipe. The longitudinal cross sectional image of the mixing of main flow and branching flows is visualized by LIF method, inserting the Rodamine B in the first branching flow. When only one branching flow is periodically injected, the fluid injected from the side flow pipe is stretched and folded by the parabolic laminar flow velocity profile and then the length of the boundary increases linearly. When branching flow is injected from multiple side flow pipe, the mixing pattern becomes more complicated. As a result, the length of the boundary increases more rapidly compared to the linear increase. The results suggest that the multiple branching flow injection enhances the mixing although no element is inserted in the pipe.

  5. Spectrophotometric determination of phosphorus in iron alloys employing a flow injection system

    Directory of Open Access Journals (Sweden)

    Gervasio Ana P. G.

    2001-01-01

    Full Text Available A flow-injection procedure for spectrophotometric determination of phosphorus in electrolytic iron and iron alloys is proposed. The method is based on the ammonium molybdate reaction followed by stannous chloride reduction in acidic medium. In order to circumvent the severe interference caused by the major constituents such as Fe(III and Cr(III, a mini-column packed with AG50W-X8 resin was coupled to the manifold. A sample throughput of 40 determinations per hour, a dynamical range from P 0.25 to 6.00 mg L-1, a reagent consumption of 25 mg ammonium molybdate and 2 mg stannous chloride per determination, and a relative standard deviation < 1% (n = 10 for a typical sample with 2.20 mg L-1 P were achieved. Three different types of samples were used to evaluate system performance. Accuracy was assessed by comparing the results with certified values and no significant difference at 95 % confidence level was observed.

  6. Development of a Fully Automated Flow Injection Analyzer Implementing Bioluminescent Biosensors for Water Toxicity Assessment

    Directory of Open Access Journals (Sweden)

    Constantinos Georgiou

    2010-07-01

    Full Text Available This paper describes the development of an automated Flow Injection analyzer for water toxicity assessment. The analyzer is validated by assessing the toxicity of heavy metal (Pb2+, Hg2+ and Cu2+ solutions. One hundred μL of a Vibrio fischeri suspension are injected in a carrier solution containing different heavy metal concentrations. Biosensor cells are mixed with the toxic carrier solution in the mixing coil on the way to the detector. Response registered is % inhibition of biosensor bioluminescence due to heavy metal toxicity in comparison to that resulting by injecting the Vibrio fischeri suspension in deionised water. Carrier solutions of mercury showed higher toxicity than the other heavy metals, whereas all metals show concentration related levels of toxicity. The biosensor’s response to carrier solutions of different pHs was tested. Vibrio fischeri’s bioluminescence is promoted in the pH 5–10 range. Experiments indicate that the whole cell biosensor, as applied in the automated fluidic system, responds to various toxic solutions.

  7. Study on the interaction of catalase with pesticides by flow injection chemiluminescence and molecular docking.

    Science.gov (United States)

    Tan, Xijuan; Wang, Zhuming; Chen, Donghua; Luo, Kai; Xiong, Xunyu; Song, Zhenghua

    2014-08-01

    The interaction mechanisms of catalase (CAT) with pesticides (including organophosphates: disulfoton, isofenphos-methyl, malathion, isocarbophos, dimethoate, dipterex, methamidophos and acephate; carbamates: carbaryl and methomyl; pyrethroids: fenvalerate and deltamethrin) were first investigated by flow injection (FI) chemiluminescence (CL) analysis and molecular docking. By homemade FI-CL model of lg[(I0-I)/I]=lgK+nlg[D], it was found that the binding processes of pesticides to CAT were spontaneous with the apparent binding constants K of 10(3)-10(5) L mol(-1) and the numbers of binding sites about 1.0. The binding abilities of pesticides to CAT followed the order: fenvalerate>deltamethrin>disulfoton>isofenphos-methyl>carbaryl>malathion>isocarbophos>dimethoate>dipterex>acephate>methomyl>methamidophos, which was generally similar to the order of determination sensitivity of pesticides. The thermodynamic parameters revealed that CAT bound with hydrophobic pesticides by hydrophobic interaction force, and with hydrophilic pesticides by hydrogen bond and van der Waals force. The pesticides to CAT molecular docking study showed that pesticides could enter into the cavity locating among the four subdomains of CAT, giving the specific amino acid residues and hydrogen bonds involved in CAT-pesticides interaction. It was also found that the lgK values of pesticides to CAT increased regularly with increasing lgP, Mr, MR and MV, suggesting that the hydrophobicity and steric property of pesticide played essential roles in its binding to CAT.

  8. [Research on optimization of mathematical model of flow injection-hydride generation-atomic fluorescence spectrometry].

    Science.gov (United States)

    Cui, Jian; Zhao, Xue-Hong; Wang, Yan; Xiao, Ya-Bing; Jiang, Xue-Hui; Dai, Li

    2014-01-01

    Flow injection-hydride generation-atomic fluorescence spectrometry was a widely used method in the industries of health, environmental, geological and metallurgical fields for the merit of high sensitivity, wide measurement range and fast analytical speed. However, optimization of this method was too difficult as there exist so many parameters affecting the sensitivity and broadening. Generally, the optimal conditions were sought through several experiments. The present paper proposed a mathematical model between the parameters and sensitivity/broadening coefficients using the law of conservation of mass according to the characteristics of hydride chemical reaction and the composition of the system, which was proved to be accurate as comparing the theoretical simulation and experimental results through the test of arsanilic acid standard solution. Finally, this paper has put a relation map between the parameters and sensitivity/broadening coefficients, and summarized that GLS volume, carrier solution flow rate and sample loop volume were the most factors affecting sensitivity and broadening coefficients. Optimizing these three factors with this relation map, the relative sensitivity was advanced by 2.9 times and relative broadening was reduced by 0.76 times. This model can provide a theoretical guidance for the optimization of the experimental conditions.

  9. Rapid Quantitation of Ascorbic and Folic Acids in SRM 3280 Multivitamin/Multielement Tablets using Flow-Injection Tandem Mass Spectrometry

    Energy Technology Data Exchange (ETDEWEB)

    Bhandari, Deepak [ORNL; Kertesz, Vilmos [ORNL; Van Berkel, Gary J [ORNL

    2013-01-01

    RATIONALE: Ascorbic acid (AA) and folic acid (FA) are water-soluble vitamins and are usually fortified in food and dietary supplements. For the safety of human health, proper intake of these vitamins is recommended. Improvement in the analysis time required for the quantitative determination of these vitamins in food and nutritional formulations is desired. METHODS: A simple and fast (~5 min) in-tube sample preparation was performed, independently for FA and AA, by mixing extraction solvent with a powdered sample aliquot followed by agitation, centrifugation, and filtration to recover an extract for analysis. Quantitative detection was achieved by flow-injection (1 L injection volume) electrospray ionization tandem mass spectrometry (ESI-MS/MS) in negative ion mode using the method of standard addition. RESULTS: Method of standard addition was employed for the quantitative estimation of each vitamin in a sample extract. At least 2 spiked and 1 non-spiked sample extract were injected in triplicate for each quantitative analysis. Given an injection-to-injection interval of approximately 2 min, about 18 min was required to complete the quantitative estimation of each vitamin. The concentration values obtained for the respective vitamins in the standard reference material (SRM) 3280 using this approach were within the statistical range of the certified values provided in the NIST Certificate of Analysis. The estimated limit of detections of FA and AA were 13 and 5.9 ng/g, respectively. CONCLUSIONS: Flow-injection ESI-MS/MS was successfully applied for the rapid quantitation of FA and AA in SRM 3280 multivitamin/multielement tablets.

  10. Amperometric electrochemical microsystem for a miniaturized protein biosensor array.

    Science.gov (United States)

    Chao Yang; Yue Huang; Hassler, B L; Worden, R M; Mason, A J

    2009-06-01

    Protein-based bioelectrochemical interfaces offer great potential for rapid detection, continuous use, and miniaturized sensor arrays. This paper introduces a microsystem platform that enables multiple bioelectrochemical interfaces to be interrogated simultaneously by an onchip amperometric readout system. A post-complementary metal-oxide semiconductor (CMOS) fabrication procedure is described that permits the formation of planar electrode arrays and self assembly of biosensor interfaces on the electrodes. The onchip, 0.5-mum CMOS readout electronics include a compact potentiostat that supports a very broad range of input currents-6 pA to 10 muA-to accommodate diverse biosensor interfaces. The 2.3 times 2.2-mm chip operates from a 5-V supply at 0.6 mA. A prototype electrochemical sensor platform, including an onchip potentiostat and miniaturized biosensor array, was characterized by using cyclic voltammetry. The linear relationship between the oxidization peak values and the concentrations of target analytes in the solution verifies functionality of the system and demonstrates the potential for future implementations of this platform in high sensitivity, low cost, and onchip protein-based sensor arrays.

  11. Electrochemical fabrication and amperometric sensor application of graphene sheets

    Science.gov (United States)

    Öztürk, Ayşe; Alanyalıoğlu, Murat

    2016-07-01

    Graphene sheets have been fabricated by applying two-step electrochemical processes in two-electrode cell system containing 0.1 M sodium dodecyl sulfate (SDS). First step is intercalation of SDS into graphite anode electrode and this process has been applied at different intercalation potential values of 1, 3, 5, and 7 V. Second step includes exfoliation of SDS-intercalated graphite electrode in the same medium by acting as cathode. Stable graphene dispersions are obtained after these two electrochemical steps. Characterization of graphene sheets have been carried out using scanning electron microscopy, electron dispersive spectroscopy, fourier transform infrared spectroscopy, UV-Vis. absorption spectroscopy, X-ray diffraction, and cyclic voltammetry techniques. Graphene sheets have been modified onto glassy carbon electrode (GCE) by drop-casting of graphene dispersion. Graphene/GCE having a good electrocatalytic activity has been used for amperometric determination of nitrite in both standard laboratory and real samples. The oxidation current density was linearly proportional to the nitrite concentration in a range between 1 and 250 μM. The sensitivity of the sensor was calculated as 0.843 μAμM-1 cm-2 with a detection limit of 0.24 μM at a signal-to-noise ratio of 3.0.

  12. Amperometric urea biosensor based on urease and electropolymerized toluidine blue dye as a pH-sensitive redox probe.

    Science.gov (United States)

    Vostiar, Igor; Tkac, Jan; Sturdik, Ernest; Gemeiner, Peter

    2002-05-15

    The electropolymerized toluidine blue film deposited on the glassy carbon electrode show amperometrically detectable pH sensitivity. This feature of polytoluidine blue (PTOB) film was used for a construction of an amperometric urea biosensor. We have observed a linear shift of the formal redox potential with increasing pH value between 4 and 8 giving the slope of 81 mV(Delta) pH(-1). Polytoluidine blue film has had a significantly increased stability and higher electrochemical activity compared to the adsorbed monomeric dye. The polytoluidine blue urea biosensor has been operating at a working potential of -200 mV vs. SCE. The sensitivity of the biosensor was 980 nA mM(-1) cm(-2). The biosensor showed linearity in concentration range up to 0.8 mM with the detection limit of 0.02 mM (S/N=3).

  13. A Nafion®-based co-planar electrode amperometric sensor for methanol determination in the gas phase

    Indian Academy of Sciences (India)

    K Wallgren; S Sotiropoulos

    2009-09-01

    A co-planar electrode device, fabricated with all electrodes (working, counter and reference) on the same face of a Nafion® polymer electrolyte membrane, is proposed for the amperometric detection of gaseous methanol using Pt as the working electrode. Clear voltammetry is obtained for methanol oxidation from its vapours in equilibrium with methanol aqueous solutions, both in the absence and presence of oxygen in the gas stream. Using an appropriate pulse sequence to keep the indicator electrode active, methanol vapours in the 1-13 Torr partial pressure range (in equilibrium with methanol aqueous solutions in the 1-10% w/w concentration range) could be determined, in a constant potential, amperometric mode. The methanol detector could be operated both in a nitrogen stream and (in what is essential for practical applications) in an air atmosphere too, with estimated detection limits of 1.2 and 1.4 Torr respectively.

  14. High-resolution quantitative metabolome analysis of urine by automated flow injection NMR.

    Science.gov (United States)

    Da Silva, Laeticia; Godejohann, Markus; Martin, François-Pierre J; Collino, Sebastiano; Bürkle, Alexander; Moreno-Villanueva, María; Bernhardt, Jürgen; Toussaint, Olivier; Grubeck-Loebenstein, Beatrix; Gonos, Efstathios S; Sikora, Ewa; Grune, Tilman; Breusing, Nicolle; Franceschi, Claudio; Hervonen, Antti; Spraul, Manfred; Moco, Sofia

    2013-06-18

    Metabolism is essential to understand human health. To characterize human metabolism, a high-resolution read-out of the metabolic status under various physiological conditions, either in health or disease, is needed. Metabolomics offers an unprecedented approach for generating system-specific biochemical definitions of a human phenotype through the capture of a variety of metabolites in a single measurement. The emergence of large cohorts in clinical studies increases the demand of technologies able to analyze a large number of measurements, in an automated fashion, in the most robust way. NMR is an established metabolomics tool for obtaining metabolic phenotypes. Here, we describe the analysis of NMR-based urinary profiles for metabolic studies, challenged to a large human study (3007 samples). This method includes the acquisition of nuclear Overhauser effect spectroscopy one-dimensional and J-resolved two-dimensional (J-Res-2D) (1)H NMR spectra obtained on a 600 MHz spectrometer, equipped with a 120 μL flow probe, coupled to a flow-injection analysis system, in full automation under the control of a sampler manager. Samples were acquired at a throughput of ~20 (or 40 when J-Res-2D is included) min/sample. The associated technical analysis error over the full series of analysis is 12%, which demonstrates the robustness of the method. With the aim to describe an overall metabolomics workflow, the quantification of 36 metabolites, mainly related to central carbon metabolism and gut microbial host cometabolism, was obtained, as well as multivariate data analysis of the full spectral profiles. The metabolic read-outs generated using our analytical workflow can therefore be considered for further pathway modeling and/or biological interpretation.

  15. Flow-injection spectrophotometric determination of cyanate in bioremediation processes by use of immobilised inducible cyanase

    Energy Technology Data Exchange (ETDEWEB)

    Luque-Almagro, V.M. [Department of Biochemistry and Molecular Biology, Edifice Severo Ochoa, Campus of Rabanales, University of Cordoba, 14071, Cordoba (Spain); Blasco, R. [Department of Biochemistry, Molecular Biology and Genetics, Veterinary School, University of Extremadura, 10071, Caceres (Spain); Fernandez-Romero, J.M.; Castro, M.D. Luque de [Department of Analytical Chemistry, Annex Edifice Marie Curie, Campus of Rabanales, University of Cordoba, 14071, Cordoba (Spain)

    2003-11-01

    A new flow injection (FI) method for photometric monitoring of cyanate in bioremediation processes using immobilised native cyanase is described. The method is based on the catalytic reaction between cyanate and bicarbonate to produce ammonia and carbon dioxide in the presence of an inducible native cyanase, immobilised in a reactor packed with glass beads. Two degrees of purification of the biocatalyst were used - heated cell-free extract and purified extract of cyanase from Pseudomonas pseudoalcaligenes CECT 5344. The ammonia produced by the enzymatic reaction is finally monitored photometrically at 700 nm using a modification of the conventional Berthelot method. The method furnishes different calibration curves depending on the degree of purification of the cyanase, with linear ranges between 1.23 and 616.50 {mu}mol L{sup -1} (r{sup 2}=0.9979, n=7) and between 1.07 and 308.25 {mu}mol L{sup -1} (r{sup 2}= 0.9992, n=7) for the heated cell-free extract and the purified cyanase extract, respectively. No statistically significant differences between the samples were found in the precision study evaluated at two cyanate concentration levels using one-way analysis of variance. A sampling frequency of 15 h{sup -1} was achieved. The method was used to monitor cyanate consumption in a cyanate bioremediation tank inoculated with Pseudomonas pseudoalcaligenes CECT 5344 strain. The correlation between cyanate degradation and ammonia production was tested using a conventional method. Finally, the method was applied to different samples collected from the bioremediation tank using the standard addition method; recoveries between 85.9 and 97.4% were obtained. (orig.)

  16. Flow-injection spectrophotometric determination of cyanate in bioremediation processes by use of immobilised inducible cyanase.

    Science.gov (United States)

    Luque-Almagro, V M; Blasco, R; Fernández-Romero, J M; de Castro, M D Luque

    2003-11-01

    A new flow injection (FI) method for photometric monitoring of cyanate in bioremediation processes using immobilised native cyanase is described. The method is based on the catalytic reaction between cyanate and bicarbonate to produce ammonia and carbon dioxide in the presence of an inducible native cyanase, immobilised in a reactor packed with glass beads. Two degrees of purification of the biocatalyst were used-heated cell-free extract and purified extract of cyanase from Pseudomonas pseudoalcaligenes CECT 5344. The ammonia produced by the enzymatic reaction is finally monitored photometrically at 700 nm using a modification of the conventional Berthelot method. The method furnishes different calibration curves depending on the degree of purification of the cyanase, with linear ranges between 1.23 and 616.50 micromol L(-1) ( r(2)=0.9979, n=7) and between 1.07 and 308.25 micro mol L(-1) ( r(2)= 0.9992, n=7) for the heated cell-free extract and the purified cyanase extract, respectively. No statistically significant differences between the samples were found in the precision study evaluated at two cyanate concentration levels using one-way analysis of variance. A sampling frequency of 15 h(-1) was achieved. The method was used to monitor cyanate consumption in a cyanate bioremediation tank inoculated with Pseudomonas pseudoalcaligenes CECT 5344 strain. The correlation between cyanate degradation and ammonia production was tested using a conventional method. Finally, the method was applied to different samples collected from the bioremediation tank using the standard addition method; recoveries between 85.9 and 97.4% were obtained.

  17. Flow injection assessment of nitrate contents in fresh and cooked fruits and vegetables grown in Fiji.

    Science.gov (United States)

    Prasad, Surendra; Chetty, Adrian A

    2011-10-01

    Nitrates form part of the essential chemistry of soils and plants. Thus, plant roots are able to absorb nitrate directly from the soil. It has been discovered that human nitrate intake is mainly from vegetables. Vegetables play an important role in human nutrition since they are an outstanding source for vitamins, minerals, and biologically active compounds. In risk assessment of nitrate contents, this study reports the nitrate levels of 8 commonly consumed fruits and vegetables grown in Fiji, tomato (Lycopersicon esculentum), eggplant (Solanum melongena), capsicum (Capsicum annuum var. grossum), breadfruit (Artocarpus altilis), long bean (Vigna sesquipedalis), jackfruit (A. heterophyllus), pumpkin (Cucurbita pepo), and cucumber (Cucumis sativus). The effects of different types of cooking methods, baking, boiling, and frying, have also been studied. The validated flow injection analysis technique has been used to quantify the nitrate-N levels in the chosen products following nitrate extraction using the activated carbon technique. The mean values of nitrate levels in fresh products ranged from 25.83 to 281.02 mg NO(3) (-) kg(-1) . The study shows that boiling reduced nitrate contents by 65.37% to 25.25%. The frying in soy bean oil elevated nitrate contents from 354.79% to 86.69%, but after baking, nitrate contents remained almost constant with slight increasing trend in the case of tomato (19.97%). The nitrate levels published in the literature for the same types of fruits and vegetables studied have also been reviewed and compared. The average nitrate-N values were comparable or lower than overseas data, but did not present unpredictably high values, that is, they were below the risk level. © 2011 Institute of Food Technologists®

  18. Phosphite determination in fertilizers after online sequential sample preparation in a flow injection system.

    Science.gov (United States)

    Dametto, Patrícia Roberta; Franzini, Vanessa Pezza; Gomes Neto, José Anchieta

    2007-07-25

    A flow injection spectrophotometric system is proposed for phosphite determination in fertilizers by the molybdenum blue method after the processing of each sample two times on-line without and with an oxidizing step. The flow system was designed to add sulfuric acid or permanganate solutions alternately into the system by simply displacing the injector-commutator from one resting position to another, allowing the determination of phosphate and total phosphate, respectively. The concentration of phosphite is obtained then by difference between the two measurents. The influence of flow rates, sample volume, and dimension of flow line connecting the injector-commutator to the main analytical channel was evaluated. The proposed method was applied to phosphite determination in commercial liquid fertilizers. Results obtained with the proposed FIA system were not statistically different from those obtained by titrimetry at the 95% confidence level. In addition, recoveries within 94 and 100% of spiked fertilizers were found. The relative standard deviation (n = 12) related to the phosphite-converted-phosphate peak alone was

  19. Very-high-flow injection rate for upper abdominal CT angiography

    Energy Technology Data Exchange (ETDEWEB)

    Kimura, Masashi; Minamiguti, Hiroki; Hagihira, Takami; Kishi, Kazushi; Sato, Morio [Wakayama Medical Coll. (Japan); Shioyama, Yasukazu; Okumura, Toshiyuki; Yamada, Kouji; Kawashima, Michihisa [Central Hospital and Cancer Center of Ibaraki Prefecture, Tomobe (Japan)

    2002-06-01

    The purpose of this study was to compare a very-high-flow injection-rate method (group A) and a conventional injection-rate method (group B) for visualization of upper abdominal arteries by multidetector helical computed tomography (MDHCT). The subjects were 240 patients suspected to have abdominal lesions. They were randomly assigned to group A (120 patients) and group B (120 patients). In group A, the bilateral medial cubital veins were punctured, and contrast medium was infused at a rate of 8.6-9.6 ml/s. In group B, the unilateral medial cubital vein was punctured, and contrast medium was infused at a rate of 2.0-3.0 ml/s. The quality of vascular visualization was graded as poor, good, or excellent by three radiologists. All visualizations of the celiac trunk (CE) and superior mesenteric artery (SMA) were graded as excellent in both group A and group B. Visualization grades of the subsegmental branches of the hepatic artery (HA), right gastric artery (RGA), cystic artery, dorsal pancreatic artery (DPA), and superior pancreaticoduodenal artery (SPDA) were good or excellent in 75% (paging method)/53.3% (three-dimensional method), 85%/30%, 77.7%/18.3%, 76.7%/28.3%, and 88.3%/42.5%, respectively, in group A, and 33.3%/11.7%, 46.7%/3.4%, 41.6%/5%, 55%/4.2%, and 72.5%/14.2%, respectively, in group B. The appearance rate of intrahepatic portal branches was 28.3% in group A and 66.7% in group B in the arterial dominant phase. Group A showed better visualization results than Group B in upper abdominal arteries according to MDHCT. (author)

  20. A Novel Amperometric Nitric Oxide Sensor Based on Polythionine /Nation Modified Glassy Carbon Electrode

    Institute of Scientific and Technical Information of China (English)

    2006-01-01

    A novel amperometric sensor for the determination of nitric oxide was developed by coating polythionine / nafion on a glassy carbon electrode. This sensor exhibited a great enhancement to the oxidation of nitric oxide. The oxidation peak currents were linear to the concentration of nitric oxide over the wide range from 3.6×10-7 to 6.8×10-5 mol. L-1, and the detection limit was 7.2×10-8 mol. L-1. Experimental results showed that this nitric oxide sensor possessed excellent selectivity and longer stability. NO releasing from rat kidney was monitored by this sensor.

  1. Simultaneous determination of Cr(III) and Cr(VI) in tannery wastewater using low pressure ion chromatography combined with flow injection spectrophotometry

    Science.gov (United States)

    Chen, Shujuan; Zhang, Xinshen; Yu, Lingyun; Wang, Li; Li, Hui

    2012-03-01

    Trivalent and hexavalent chromium have been successfully separated and determined using low pressure ion chromatography combined with flow injection spectrophotometric analysis (LPIC-FIA). A column packed with crosslinking starch microspheres was used for on-line separation of Cr(III) from Cr(VI) in a flow-injection system because of its absorptive effect on Cr(III). To determine the concentration of Cr(III) and Cr(VI) in samples, we used 3.0 mmol/L nitric acid to elute adsorbed Cr(III) from the column and then used ceric sulfate-sulfuric acid as oxidant to convert all Cr(III) into Cr(VI). Then, Cr(VI) directly came from the samples and Cr(VI) came from Cr(III) successively formed a amaranthine complex with diphenycarbazide and the complex shows a maximum absorption at 530 nm. Analytical parameters including the concentration of eluent and oxidant solution, oxidizing temperature, length of oxidizing reaction coil, reaction coil and injection coil, interfering effects, etc., were optimized. The limit of detection was 1.25 μg/L for Cr(VI) and 3.76 μg/L for Cr(III). The linear relationship between absorption with the concentration of Cr(VI) and Cr(III) was 0.001-1.000 mg/L and 0.030-1.000 mg/L with correlation coefficients of 0.9995 and 0.9994, respectively. The relative standard deviation of Cr(VI) and Cr(III) was 1.21% and 1.66%, respectively (n = 10). Major cations and anions did not show any interference. We validated this method through certified reference materials and through measuring the recovery in tannery wastewater.

  2. Bioethanol in Biofuels Checked by an Amperometric Organic Phase Enzyme Electrode (OPEE Working in “Substrate Antagonism” Format

    Directory of Open Access Journals (Sweden)

    Mauro Tomassetti

    2016-08-01

    Full Text Available The bioethanol content of two samples of biofuels was determined directly, after simple dilution in decane, by means of an amperometric catalase enzyme biosensor working in the organic phase, based on substrate antagonisms format. The results were good from the point of view of accuracy, and satisfactory for what concerns the recovery test by the standard addition method. Limit of detection (LOD was on the order of 2.5 × 10−5 M.

  3. The impact of flow injection on modem chemical analysis: has it fulfilled our expectations? And where are we going?

    DEFF Research Database (Denmark)

    Hansen, Elo Harald

    2004-01-01

    Presenting a condensation of the opening lecture of the 12th ICFIA conference, this communication presents a view of the impact that flow injection analysis (FIA) has had on modern analytical chemistry, evaluated both within the academic community and outside it, i.e., in “industry”. The ensuing ...... developments of FIA, encompassing sequential injection analysis (SIA) and bead injection lab-on-valve (BI-LOV), are described and their individual features discussed. Finally some recent results of the activities from the author’s own research group are briefly mentioned.......Presenting a condensation of the opening lecture of the 12th ICFIA conference, this communication presents a view of the impact that flow injection analysis (FIA) has had on modern analytical chemistry, evaluated both within the academic community and outside it, i.e., in “industry”. The ensuing...

  4. Flow injection spectrophotometry coupled with a crushed barium sulfate reactor column for the determination of sulfate ion in water samples

    OpenAIRE

    Burakham,Rodjana; Higuchi, Keiro; Oshima, Mitsuko; Grudpan, Kate; Motomizu, Shoji

    2004-01-01

    A new type of a reactor column, a crushed BaSO4 reactor column used for the flow injection spectrophotometric determination of sulfate ion using the exchange reaction of sulfate ion and barium-dimethylsulfonazo III is proposed. The column is very simple and economical. It can be continuously used for 8 h before washing with water for repeated usage of at least 1 month. The procedure is sensitive. Application to various water samples was demonstrated.

  5. Ionophore-Based Potentiometric Sensors for the Flow-Injection Determination of Promethazine Hydrochloride in Pharmaceutical Formulations and Human Urine

    Directory of Open Access Journals (Sweden)

    Suad Mustafa Al-Araji

    2011-01-01

    Full Text Available Plasticised poly(vinyl chloride-based membranes containing the ionophores (α-, β- and γ-cyclodextrins (CD, dibenzo-18-crown-6 (DB18C6 and dibenzo-30-crown-10 (DB30C10 were evaluated for their potentiometric response towards promethazine (PM in a flow injection analysis (FIA set-up. Good responses were obtained when β- and γ-CDs, and DB30C10 were used. The performance characteristics were further improved when tetrakis(4-chlorophenyl borate (KTPB was added to the membrane. The sensor based on β-CD, bis(2-ethylhexyl adipate (BEHA and KTPB exhibited the best performance among the eighteen sensor compositions that were tested. The response was linear from 1 x 10−5 to 1 x 10−2 M, slope was 61.3 mV decade−1, the pH independent region ranged from 4.5 to 7.0, a limit of detection of 5.3 x 10−6 M was possible and a lifetime of more than a month was observed when used in the FIA system. Other plasticisers such as dioctyl phenylphosphonate and tributyl phosphate do not show significant improvements in the quality of the sensors. The promising sensors were further tested for the effects of foreign ions (Li+, Na+, K+, Mg2+, Ca2+, Co2+, Cu2+, Cr3+, Fe3+, glucose, fructose. FIA conditions (e.g., effects of flow rate, injection volume, pH of the carrier stream were also studied when the best sensor was used (based on β-CD. The sensor was applied to the determination of PM in four pharmaceutical preparations and human urine that were spiked with different levels of PM. Good agreement between the sensor and the manufacturer’s claimed values (for pharmaceutical preparations was obtained, while mean recoveries of 98.6% were obtained for spiked urine samples. The molecular recognition features of the sensors as revealed by molecular modelling were rationalised by the nature of the interactions and complexation energies between the host and guest molecules.

  6. A multisyringe flow injection method for the automated determination of sulfide in waters using a miniaturised optical fiber spectrophotometer.

    Science.gov (United States)

    Ferrer, Laura; de Armas, Graciela; Miró, Manuel; Estela, José Manuel; Cerdà, Víctor

    2004-12-15

    In this paper, a fully software-controlled multisyringe flow injection (MSFIA) spectrophotometric system is proposed for the determination of sulfide in environmental and waste waters. The implementation of ancillary solenoid valves into the flow network allows a multitude of injection modalities to be explored, the selected modality being directly dependent on the aim of the assays. The multicommuted sandwich-type approach is introduced in this work as an efficient means to warrant high sensitivity for the particular assay with excellent repeatabilities and a considerable reagent saving. Moreover, a high injection frequency may be easily attained by carrying out a multiple injection modality during a single forward displacement of the piston driver bar. The interfacing of the robust and versatile multisyringe piston pump with an optical fiber plug-in spectrophotometer furnished with a light emitting diode enables the miniaturization of the flow analyzer, which is thus readily adaptable to in-situ and real-time monitoring schemes. The flow method is based on the coupling Fischer's reaction of sulfide with N,N-dimethyl-p-phenylenediamine in the presence of Fe(III) as oxidizing reagent in a 0.7M HCl medium. Careful selection of the physical and chemical variables enabled coefficients of variations better than 1.5% (n = 10) at the 1mgl(-1) level for both injection modalities. Dynamic working ranges of 0.2-2.0 and 0.5-5mgl(-1) sulfide for sandwich and multiple injection techniques, and detection limits of 0.09 and 0.15mgl(-1), respectively, were obtained. Furthermore, the sandwich modality featured an average slope of 0.43 +/- 0.02lmg(-1) calculated from 10 day-to-day calibration plots. This result reveals better sensitivity than other flowing stream methods described in the literature. The multiple injection technique allowed an improvement of the injection throughput up to 80h(-1), although a decrease of sensitivity was concomitantly observed (average slope of 0

  7. Miniaturized flow system based on enzyme modified PMMA microreactor for amperometric determination of glucose.

    Science.gov (United States)

    Cerdeira Ferreira, Luís Marcos; da Costa, Eric Tavares; do Lago, Claudimir Lucio; Angnes, Lúcio

    2013-09-15

    This paper describes the development of a microfluidic system having as main component an enzymatic reactor constituted by a microchannel assembled in poly(methyl methacrylate) (PMMA) substrate connected to an amperometric detector. A CO2 laser engraving machine was used to make the channels, which in sequence were thermally sealed. The internal surfaces of the microchannels were chemically modified with polyethyleneimine (PEI), which showed good effectiveness for the immobilization of the glucose oxidase enzyme using glutaraldehyde as crosslinking agent, producing a very effective microreactor for the detection of glucose. The hydrogen peroxide generated by the enzymatic reaction was detected in an electrochemical flow cell localized outside of the reactor using a platinum disk as the working electrode. The proposed system was applied to the differential amperometric determination of glucose content in soft drinks showing good repeatability (DPR=1.72%, n=50), low detection limit (1.40×10(-6)molL(-1)), high sampling frequency (calculated as 345 samples h(-1)), and relatively good stability for long-term use. The results were in close agreement with those obtained by the classical spectrophotometric method utilized to quantify glucose in biological fluids.

  8. Preparation of an amperometric sensor for norfloxacin based on molecularly imprinted grafting photopolymerization.

    Science.gov (United States)

    Wang, Zhihua; Li, Jinshu; Liu, Xiaole; Yang, Jianming; Lu, Xiaoquan

    2013-03-01

    A sensitive amperometric sensor for norfloxacin (NF) was introduced. The receptor layer was prepared by molecularly imprinted photopolymerization of acrylamide and trimethylolpropane trimethacrylate on the surface of a gold electrode. The binding mechanism of the molecularly imprinted polymer was explored by ultraviolet (UV) and infrared (IR) spectroscopy. The chemosensor was characterized by cyclic voltammetry (CV), differential pulse voltammetry (DPV), electrochemical impedance (EI), and scanning electron microscopy (SEM). The electrode prepared by photopolymerization has a better recognition ability to template molecules than that of electropolymerization and NIP. Some parameters affecting sensor response were optimized. Norfloxacin was detected by measurements of an amperometric i-t curve. The linear relationships between current and logarithmic concentration are obtained from 1.0 × 10(-9) to 1.0 × 10(-3) mol L(-1). The detection limit of the sensor was 1.0 × 10(-10) mol L(-1). The proposed method is sensitive, simple, and cheap, and is applied to detect NF in human urine successfully.

  9. Amperometric Biosensor for Hydrogen Peroxide Based on Electrodeposited Sub-micrometer Gold Modified Glassy Carbon Electrode

    Institute of Scientific and Technical Information of China (English)

    WANG,Shu-Qing(王树青); CHEN,Jun(陈峻); LIN,Xiang-Qin(林祥钦)

    2004-01-01

    A new type of hydrogen peroxide amperometric biosensor was fabricated based on electrochemically deposited sub-micrometer Au particles(sm-Au)on a glassy carbon electrode(GCE).Electrochemical deposition condition was optimized for obtaining uniformly distributed sub-micrometer sized Au array on the electrode surface.The hydrogen peroxide sensor was fabricated by adsorbing phenothiazine methylene blue(MB)molecules on the surface of sm-Au and covering a cross-linked horseradish peroxidase(HRP)layer,labeled as HRP/MB/sm-Au/GCE.The characteristics of this biosensor were evaluated with respect to applied potential and pH.The amperometric response of the sensor was linear to the H2O2 concentration over a wide range of 9.9×10-6-1.11×10-2 mol/L.A detection limit(s/n=3)of 3.0×10-6 mol/L H2O2 was estimated for a sampled chronoamperometric detection at 1.5 min after potential step of 200 to-400 mV vs.SCE.The immobilized MB molecules shuttled electrons at(=0.77 and an apparent electron transfer rate constant of =0.053 s-1.Interference of ascorbic acid,dopamine and uric acid was investigated.This sensor has very good stability and reproducibility for long-term use.

  10. Current Fluctuation Measurements of Amperometric Gas Sensors Constructed with Three Different Technology Procedures

    Directory of Open Access Journals (Sweden)

    Sedlak Petr

    2016-12-01

    Full Text Available Electrochemical amperometric gas sensors represent a well-established and versatile type of devices with unique features: good sensitivity and stability, short response/recovery times, and low power consumption. These sensors operate at room temperature, and therefore have been applied in monitoring air pollutants and detection of toxic and hazardous gases in a number of areas. Some drawbacks of classical electrochemical sensors are overcome by the solid polymer electrolyte (SPE based on ionic liquids. This work presents evaluation of an SPE-based amperometric sensor from the point of view of current fluctuations. The sensor is based on a novel three-electrode sensor platform with solid polymer electrolytes containing ionic liquid for detection of nitrogen dioxide − a highly toxic gas that is harmful to the environment and presenting a possible threat to human health even at low concentrations. The paper focuses on using noise measurement (electric current fluctuation measurement for evaluation of electrochemical sensors which were constructed by different fabrication processes: (i lift-off and drop-casting technology, (ii screen printing technology on a ceramic substrate and (iii screen printing on a flexible substrate.

  11. Development of Amperometric Biosensors Based on Nanostructured Tyrosinase-Conducting Polymer Composite Electrodes

    Directory of Open Access Journals (Sweden)

    Francisco Javier del Campo

    2013-05-01

    Full Text Available Bio-composite coatings consisting of poly(3,4-ethylenedioxythiophene (PEDOT and tyrosinase (Ty were successfully electrodeposited on conventional size gold (Au disk electrodes and microelectrode arrays using sinusoidal voltages. Electrochemical polymerization of the corresponding monomer was carried out in the presence of various Ty amounts in aqueous buffered solutions. The bio-composite coatings prepared using sinusoidal voltages and potentiostatic electrodeposition methods were compared in terms of morphology, electrochemical properties, and biocatalytic activity towards various analytes. The amperometric biosensors were tested in dopamine (DA and catechol (CT electroanalysis in aqueous buffered solutions. The analytical performance of the developed biosensors was investigated in terms of linear response range, detection limit, sensitivity, and repeatability. A semi-quantitative multi-analyte procedure for simultaneous determination of DA and CT was developed. The amperometric biosensor prepared using sinusoidal voltages showed much better analytical performance. The Au disk biosensor obtained by 50 mV alternating voltage amplitude displayed a linear response for DA concentrations ranging from 10 to 300 μM, with a detection limit of 4.18 μM.

  12. Determinação turbidimétrica em fluxo de cloridrato de fluoxetina em formulações farmacêuticas Flow-injection turbidimetric determination of fluoxetine hydrochloride in pharmaceutical formulations

    Directory of Open Access Journals (Sweden)

    Willian Toito Suarez

    2009-01-01

    Full Text Available A simple, accurate and precise flow-injection turbidimetric procedure for the determination of fluoxetine hydrochloride in pharmaceutical formulations is reported. The procedure is based on the precipitation of chloride of fluoxetine hydrochloride with silver nitrate solution and the yielded insoluble AgCl(s was monitored at 420 nm. The analytical curve was linear in the fluoxetine hydrochloride concentration range 3.0 x 10-5 - 5.0 x 10-4 mol L-1 with a detection limit of 10 µmol L-1 and, a sample throughout of 60 h-1.

  13. Coupling on-line preconcentration by ion-exchange with ETAAS. A novel flow injection approach based on the use of a renewable microcolumn as demonstrated for the determination of nickel in environmental and biological samples

    DEFF Research Database (Denmark)

    Wang, Jianhua; Hansen, Elo Harald

    2000-01-01

    A novel way of exploiting flow injection/sequential injection (FIA/SIA) on-line ion-exchange preconcentration with detection by electrothermal atomic absorption spectrometry (ETAAS) is described and demonstrated for the determination of trace-levels of nickel. Based on the use of a renewable...... microcolumn incorporated within an integrated micro FI-system, the column is loaded with a defined volume of small beads of an SP Sephadex C-25 cation-exchange resin and subsequently exposed to a metered amount of sample solution. However, instead of eluting the retained analyte from the organic ion-exchange...

  14. Homemade Bienzymatic-Amperometric Biosensor for Beverages Analysis

    Science.gov (United States)

    Blanco-Lopez, M. C.; Lobo-Castanon, M. J.; Miranda-Ordieres, A. J.

    2007-01-01

    The construction of an amperometric biosensor for glucose analysis is described demonstrating that the analysis is easy to perform and the biosensor gives good analytical performance. This experiment helped the students to acquire problem-solving and teamwork skills, allowing them to reach a high level of independent and critical thought.

  15. 0.3 MM Diameter Flexible Amperometric Lactate Probe.

    Science.gov (United States)

    1993-01-26

    also the oxidation of the FADH 2 by 02, whereby H202 is formed. LOX-FAD + Lactate -, Pvruvate + LOX-FADH2 (1) Amperometric lactate sensors have been...tile reduced forms of a diffusional mediator, such :is 0- H-,O, or Fc-/Fc (where Fc is a ferrocene derivativei. 5 -10 FAD/ FADH - centers of LOX were also

  16. Amperometric hydrogen peroxide and glucose biosensor based on NiFe2/ordered mesoporous carbon nanocomposites.

    Science.gov (United States)

    Xiang, Dong; Yin, Longwei; Ma, Jingyun; Guo, Enyan; Li, Qun; Li, Zhaoqiang; Liu, Kegao

    2015-01-21

    Nanocomposites of NiFex embedded in ordered mesoporous carbon (OMC) (x = 0, 1, 2) were prepared by a wet impregnation and hydrogen reduction process and were used to construct electrochemical biosensors for the amperometric detection of hydrogen peroxide (H2O2) or glucose. The NiFe2/OMC nanocomposites were demonstrated to have a large surface area, suitable mesoporous channels, many edge-plane-like defective sites, and a good distribution of alloyed nanoparticles. The NiFe2/OMC and Nafion modified glass carbon electrode (GCE) exhibited excellent electrocatalytic activities toward the reduction of H2O2 as well. By utilizing it as a bioplatform, GOx (glucose oxidase) cross-linked with Nafion was immobilized on the surface of the electrode for the construction of an amperometric glucose biosensor. Our results indicated that the amperometric hydrogen peroxide biosensor (NiFe2/OMC + Nafion + GCE) showed good analytical performances in term of a high sensitivity of 4.29 μA mM(-1) cm(-2), wide linearity from 6.2 to 42,710 μM and a low detection limit of 0.24 μM at a signal-to-noise ratio of 3 (S/N = 3). This biosensor exhibited excellent selectivity, high stability and negligible interference for the detection of H2O2. In addition, the immobilized enzyme on NiFe2/OMC + Nafion + GCE, retaining its bioactivity, exhibited a reversible two-proton and two-electron transfer reaction, a fast heterogeneous electron transfer rate and an effective Michaelis-Menten constant (K) (3.18 mM). The GOx + NiFe2/OMC + Nafion + GCE could be used to detect glucose based on the oxidation of glucose catalyzed by GOx and exhibited a wide detection range of 48.6-12,500 μM with a high sensitivity of 6.9 μA mM(-1) cm(-2) and a low detection limit of 2.7 μM (S/N = 3). The enzymic biosensor maintained a high selectivity and stability features, and shows great promise for application in the detection of glucose.

  17. Method for the simultaneous determination of total polyphenol and anthocyan indexes in red wines using a flow injection approach

    OpenAIRE

    2002-01-01

    A simultaneous and fast method for the determination of total polyphenol index (t.p.i.) and total anthocyan index (t.a.i.) has been developed by a flow injection approach and a diode array spectrophotometer for monitoring at 280 nm and 520 nm, respectively. Linear ranges were obtained from 20 to 70 index units and from 20 to 500 mg l-1 for t.p.i. and t.a.i., respectively. The results provided by the proposed method agree with those obtained using the polyphenol index at 280 nm and the Riberea...

  18. Feedback-amplified electrochemical dual-plate boron-doped diamond microtrench detector for flow injection analysis

    Science.gov (United States)

    Lewis, Grace E M; Gross, Andrew J; Kasprzyk-Hordern, Barbara; Lubben, Anneke T; Marken, Frank

    2015-01-01

    An electrochemical flow cell with a boron-doped diamond dual-plate microtrench electrode has been developed and demonstrated for hydroquinone flow injection electroanalysis in phosphate buffer pH 7. Using the electrochemical generator-collector feedback detector improves the sensitivity by one order of magnitude (when compared to a single working electrode detector). The diffusion process is switched from an analyte consuming “external” process to an analyte regenerating “internal” process with benefits in selectivity and sensitivity. PMID:25735831

  19. Simultaneous determination of nanomole amounts of sulphur dioxide and hydrogen sulphide by flow injection analysis with on-line preconcentration by means of capillary denuder tubes.

    Science.gov (United States)

    Achilli, Marco; Gács, Istvan

    2002-01-01

    A simple and rapid method for trace determination of SO2 and H2S in gaseous samples by using a flow injection system with on line preconcentration on capillary denuder is described. The gaseous samples are led through a 0.4 M sulphamic acid solution, retaining nitrogen dioxide, ammonia and hydrogen chloride. The sulphur dioxide is collected from the carrier gas stream (250 cm3 min-1) as sulphuric acid in a capillary denuder tube coated with a thin layer of 0.01-0.03 M hydrogen peroxide solution of 0.05 mM sulphuric acid; hydrogen sulphide passes into a second tube coated with 0.075 mM sodium sulphide solution of 0.1 M aqueous sodium hydroxide. The films containing the sulphuric acid and the sodium sulphide, respectively, are eluted with the corresponding circulating absorbent streams and pass through the detectors. Sulphuric acid is detected by conductimetry and sulphide is determined spectrophotometrically at 230 nm. If nanoequivalent amounts of H2S are present in the sample containing a large concentration of SO2 (SO2/H2S concentration ratio > 20), the sulphur dioxide is filtered out of the sample gas stream by solid sodium hydrogen carbonate. A limit of detection of 3.5 micrograms m-3 is obtained.

  20. Preparation of Fe(3)O(4)@C@CNC multifunctional magnetic core/shell nanoparticles and their application in a signal-type flow-injection photoluminescence immunosensor.

    Science.gov (United States)

    Chu, Chengchao; Li, Meng; Li, Long; Ge, Shenguang; Ge, Lei; Yu, Jinghua; Yan, Mei; Song, Xianrang

    2013-11-01

    We describe here the preparation of carbon-coated Fe3O4 magnetic nanoparticles that were further fabricated into multifunctional core/shell nanoparticles (Fe3O4@C@CNCs) through a layer-by-layer self-assembly process of carbon nanocrystals (CNCs). The nanoparticles were applied in a photoluminescence (PL) immunosensor to detect the carcinoembryonic antigen (CEA), and CEA primary antibody was immobilized onto the surface of the nanoparticles. In addition, CEA secondary antibody and glucose oxidase were covalently bonded to silica nanoparticles. After stepwise immunoreactions, the immunoreagent was injected into the PL cell using a flow-injection PL system. When glucose was injected, hydrogen peroxide was obtained because of glucose oxidase catalysis and quenched the PL of the Fe3O4@C@CNC nanoparticles. The here proposed PL immunosensor allowed us to determine CEA concentrations in the 0.005–50 ng·mL-1 concentration range, with a detection limit of 1.8 pg·mL-1.

  1. On-line monitoring of the photocatalytic degradation of 2,4-D and dicamba using a solid-phase extraction-multisyringe flow injection system.

    Science.gov (United States)

    Chávez-Moreno, Carmín; Ferrer, Laura; Hinojosa-Reyes, Laura; Hernández-Ramírez, Aracely; Cerdà, Víctor; Guzmán-Mar, Jorge

    2013-11-15

    A fully automated on-line system for monitoring the photocatalytic degradation of herbicides was developed using multisyringe flow injection analysis (MSFIA) coupled to a solid phase extraction (SPE) unit with UV detection. The calibration curves were linear in the concentration range of 100-1000 μg L(-1) for 3,6-dichloro-2-methoxybenzoic acid (dicamba) and 500-3000 μg L(-1) for 2,4-dichlorophenoxyacetic acid (2,4-D), while the detection limits were 30 and 135 μg L(-1) for dicamba and 2,4-D, respectively. The monitoring of the photocatalytic degradation (TiO2 anatase/UV 254 nm) of these two herbicides was performed by MSFIA-SPE system using a small sample volume (2 mL) in a fully automated approach. The degradation was assessed in ultrapure and drinking water with initial concentrations of 1000 and 2000 μg L(-1) for dicamba and 2,4-D, respectively. Degradation percentages of approximately 85% were obtained for both herbicides in ultrapure water after 45 min of photocatalytic treatment. A similar degradation efficiency in drinking water was observed for 2,4-D, whereas dicamba exhibited a lower degradation percentage (75%), which could be attributed to the presence of inorganic species in this kind of water. Copyright © 2013 Elsevier Ltd. All rights reserved.

  2. A microchip-based flow injection-amperometry system with mercaptopropionic acid modified electroless gold microelectrode for the selective determination of dopamine.

    Science.gov (United States)

    Wang, Yi; Luo, Jie; Chen, Hengwu; He, Qiaohong; Gan, Nin; Li, Tianhua

    2008-09-12

    A novel chip-based flow injection analysis (FIA) system has been developed for automatic, rapid and selective determination of dopamine (DA) in the presence of ascorbic acid (AA). The system is composed of a polycarbonate (PC) microfluidic chip with an electrochemical detector (ED), a gravity pump, and an automatic sample loading and injection unit. The selectivity of the ED was improved by modification of the gold working microelectrode, which was fabricated on the PC chip by UV-directed electroless gold plating, with a self-assembled monolayer (SAM) of 3-mercaptopropionic acid (MPA). Postplating treatment methods for cleaning the surface of electroless gold microelectrodes were investigated to ensure the formation of high quality SAMs. The effects of detection potential, flow rate, and sampling volume on the performance of the chip-based FIA system were studied. Under optimum conditions, a detection limit of 74 nmol L(-1) for DA was achieved at the sample throughput rate of 180 h(-1). A RSD of 0.9% for peak heights was observed for 19 runs of a 100 micromol L(-1) DA solution. Interference-free determination of DA could be conducted if the concentration ratio of AA-DA was no more than 10.

  3. The use of a polymer inclusion membrane as a sorbent for online preconcentration in the flow injection determination of thiocyanate impurity in ammonium sulfate fertilizer.

    Science.gov (United States)

    Ohshima, Takumi; Kagaya, Shigehiro; Gemmei-Ide, Makoto; Cattrall, Robert W; Kolev, Spas D

    2014-11-01

    A polymer inclusion membrane (PIM) is used for the first time as a sorbent in the construction of a preconcentration column to enhance the sensitivity in flow injection analysis (FIA). The PIM-coated column is readily prepared by coating the PIM containing poly(vinyl chloride), Aliquat 336, and 1-tetradecanol onto glass beads packed in a glass tube. The determination of trace amounts of thiocyanate in ammonium sulfate fertilizer demonstrates the potential of the proposed PIM-coated column in FIA. Thiocyanate standards or samples of relatively large volume (e.g. up to 2000 µL) are injected into a nitrate carrier stream. The sample zone passes through the proposed preconcentration column where thiocyanate is concentrated in a smaller volume of a carrier solution thus resulting in up to 7.4 fold increase in sensitivity. Thiocyanate is detected spectrophotometrically after its reaction with Fe(III) downstream of the preconcentration column. The limits of detection of thiocyanate in the absence and presence of 20 g L(-1) ammonium sulfate (S/N=2) are 0.014 and 0.024 mg L(-1), respectively. Thiocyanate was successfully determined in several samples of ammonium sulfate fertilizer.

  4. [Determination of a Candida albicans antigen using an amperometric immunoenzyme sensor].

    Science.gov (United States)

    Kutyreva, M P; Mediantseva, E P; Khaldeeva, E V; Glushko, N I; Budnikov, G K

    1998-01-01

    Determination new variant enzyme immunoassay with amperometric enzyme immunosensor, including the immobilizing enzyme-choline esterase and antibodies against Candida albicans (CA) in biosensitivity part of sensor, for diagnose disease of CA. The method for determination of CA based on combination immunochemical reactions and voltammetric indication of analytical signal was developed. Amperometric enzyme immunosensor developed has been used as detector. Differences dilutions of antibody (Ab) against antigen (Ag) of CA immobilizing in common with choline esterase (CE). The method of immobilization developed allows to receive the sensor with including the immobilized CE and Ab in common. The method of determination of CA based on combination the reaction of forming immune complex tAb-AgI with enzyme immunosensor for its detection. The dynamic range of concentrations determined of Ag depends on degree of dilution of Ab used for manufactory biosensitivity part of sensor. The data indicate that the [Ab-Ag] immune complexes are stable. This is also confirmed by the values of [Ab-Ag] binding constants, obtained in Scatchard coordinates. This method of determination doesn't require special preparation of a sample. Selectivity, sensitivity, simplicity and quickness are characterize of this method which could be used for manufacturing test-sistem for determination CA in blood.

  5. Fabrication of amperometric xanthine biosensors based on direct chemistry of xanthine oxidase

    Energy Technology Data Exchange (ETDEWEB)

    Gao Yansheng; Shen Chunping [Department of Chemistry, Soochow University, Suzhou, Jiangsu 215123 (China); Di Junwei, E-mail: djw@suda.edu.cn [Department of Chemistry, Soochow University, Suzhou, Jiangsu 215123 (China); Tu Yifeng [Department of Chemistry, Soochow University, Suzhou, Jiangsu 215123 (China)

    2009-08-31

    The construction of amperometric xanthine biosensor by immobilization of xanthine oxidase (XOD) on the multi-wall carbon nanotubes (CNTs) modified glassy carbon (GC) electrode surface was investigated. The direct chemistry of XOD was accomplished and the formal potential was about - 0.465 V (vs SCE). The heterogeneous electron transfer rate constant was evaluated to be 2.0 {+-} 0.3 s{sup -1}. The xanthine biosensor based on XOD entrapped in silica sol-gel (SG) thin film on CNTs-modified GC electrode surface was also investigated. The XOD still maintains its activity to xanthine. The amperometric response to xanthine showed a linear relation in the range from 0.2 {mu}M to 10 {mu}M and a detection limit of 0.1 {mu}M (S/N = 3). The enzyme electrode retained 95% of its initial activity after 90 days of storage. The sensor exhibited high sensitivity, rapid response and good long-term stability.

  6. Development of urease based amperometric biosensors for the inhibitive determination of Hg (II).

    Science.gov (United States)

    Domínguez-Renedo, O; Alonso-Lomillo, M A; Ferreira-Gonçalves, L; Arcos-Martínez, M J

    2009-10-15

    Enzymatic amperometric procedures for measurement of Hg (II), based on the inhibitive action of this metal on urease enzyme activity, were developed. Screen-printed carbon electrodes (SPCEs) and gold nanoparticles modified screen-printed carbon electrodes (AuNPs/SPCEs) were used as supports for the cross-linking inmobilization of the enzyme urease. The amperometric response of urea was affected by the presence of Hg (II) ions which caused a decreasing in the current intensity. The optimum working conditions were found using experimental design methodology. Under these conditions, repeatability and reproducibility for both types of biosensors were determined, reaching values below 6% in terms of residual standard deviation. The detection limit obtained for Hg (II) was 4.2x10(-6)M for urease/SPCE biosensor and 5.6x10(-8)M for urease/AuNPs/SPCE biosensor. Analysis of the possible effect of the presence of foreign ions in the solution was performed. The method was applied to determine levels of Hg (II) in spiked human plasma samples.

  7. Amperometric biosensors for glucose, lactate, and glycolate based on oxidases and redox-modified siloxane polymers

    Science.gov (United States)

    Hale, Paul D.; Inagaki, Toru; Lee, Hung Sui; Skotheim, Terje A.; Karan, Hiroko I.; Okamoto, Yoshi

    1989-06-01

    Amperometric biosensors based on flavin-containing oxidases undergo several steps which produce a measurable current that is related to the concentration of substrate. In the initial step, the substrate converts the oxidized flavin adenine dinucleotide (FAD) or flavin mononucleotide (FMN) into the reduced form FADH sub 2 or FMNH sub 2. Because these cofactors are located well within the enzyme molecule, direct electron transfer to the surface of a conventional electrode does not occur to a measurable degree. A common method of facilitating this electron transfer is to introduce oxygen into the system because it is the natural acceptor for the oxidases; the oxygen is reduced by the FADH sub 2 or FMNH sub 2 to hydrogen peroxide, which can then be detected electrochemically. The major drawback to this approach is the fact that oxidation of hydrogen peroxide requires a large overpotential, thus making these sensors susceptible to interference from electroactive species. To lower the necessary applied potential, several non-physiological redox couples have been employed to shuttle electrons between the flavin moieties and the electrode. The present paper describes the development of amperometric biosensors based on flavin-containing enzymes and a family of polymeric mediators.

  8. Detection of dopamine in non-treated urine samples using glassy carbon electrodes modified with PAMAM dendrimer-Pt composites

    Energy Technology Data Exchange (ETDEWEB)

    Garcia, M.G. [Laboratory of Bioelectrochemistry, Centro de Investigacion y Desarrollo Tecnologico en Electroquimica, S. C., Parque Tecnologico, Queretaro, Sanfandila, Pedro Escobedo 76703, Queretaro (Mexico); Department of Chemistry, Universidad de Guanajuato, Cerro de la Venada S/N Col. Pueblito de Rocha, 36040 Guanajuato, Gto (Mexico); Armendariz, G.M.E.; Godinez, Luis A.; Torres, J. [Laboratory of Bioelectrochemistry, Centro de Investigacion y Desarrollo Tecnologico en Electroquimica, S. C., Parque Tecnologico, Queretaro, Sanfandila, Pedro Escobedo 76703, Queretaro (Mexico); Sepulveda-Guzman, S. [Centro de Innovacion, Investigacion y Desarrollo en Ingenieria y Tecnologia, Facultad de Ingenieria Mecanica y Electrica, Universidad Autonoma de Nuevo Leon, Av. Universidad, San Nicolas de los Garza, Nuevo Leon, 66451 Nuevo Leon (Mexico); Bustos, E., E-mail: ebustos@cideteq.mx [Laboratory of Bioelectrochemistry, Centro de Investigacion y Desarrollo Tecnologico en Electroquimica, S. C., Parque Tecnologico, Queretaro, Sanfandila, Pedro Escobedo 76703, Queretaro (Mexico)

    2011-09-01

    Composites of hydroxyl-terminated PAMAM dendrimers, generation 4.0 (64 peripheral OH groups) containing Pt nanoparticles were synthesized at different reaction times using a microwave reactor. The synthetic procedure resulted in dendrimer encapsulated nanoparticles of Pt (DENs-Pt) of 1.53 {+-} 0.17 nm diameter that was calculated from transmission electron microscopy, and the Pt nanoparticles had single crystal plane in (1 1 1) orientation determinate by selective area diffraction. Each composite was electrochemically immobilized on a pre-functionalized glassy carbon (GC) electrode that was incorporated as a flow injection amperometric (FIA) detector, for the selective detection and quantification of dopamine (DA) in untreated urine samples. Comparison of the analytical performance of the novel electrochemical detector revealed that the DENs-Pt modified GC electrode with the composite synthesized for 30 min in the microwave reactor, showed the best response for the detection of DA in samples of non-treated urine, being the detection and quantification limits smaller (19 and 9 ppb, respectively) than those corresponding to the naked a GC electrode (846 and 423 ppb, respectively) using the FIA detector. In addition, it was found that this electroanalytical approach suffers minimal matrix effects that arise in the analysis of DA in untreated samples of urine.

  9. Separation and quantification of inulin in selected artichoke (Cynara scolymus L.) cultivars and dandelion (Taraxacum officinale WEB. ex WIGG.) roots by high-performance anion exchange chromatography with pulsed amperometric detection.

    Science.gov (United States)

    Schütz, Katrin; Muks, Erna; Carle, Reinhold; Schieber, Andreas

    2006-12-01

    The profile of fructooligosaccharides and fructopolysaccharides in artichoke heads and dandelion roots was investigated. For this purpose, a suitable method for high-performance anion exchange chromatography with pulsed amperometic detection was developed. The separation of monomers, oligomers and polymers up to a chain length of 79 sugar residues was achieved in one single run. Glucose, fructose, sucrose and individual fructooligosaccharides (kestose, nystose, fructofuranosylnystose) were quantified in six different artichoke cultivars and in dandelion roots. The contents ranged from 12.9 g/kg DM to 71.7 g/kg DM for glucose, from 15.8 g/kg DM to 67.2 g/kg DM for fructose, and from 16.8 g/kg DM to 55.2 g/kg DM for sucrose in the artichoke heads. Kestose was the predominant fructooligosaccharide, followed by nystose and fructofuranosylnystose. In four cultivars fructofuranosylnystose was only detectable in traces and reached its maximum value of 3.6 g/kg DM in the cultivar Le Castel. Furthermore, an average degree of polymerization of 5.3 to 16.7 was calculated for the individual artichoke cultivars, which is noticeably lower than hitherto reported. In contrast, the contents of kestose, nystose and fructofuranosylnystose in dandelion root exceeded that of artichoke, reflecting the short chain characteristic of the inulin, which was confirmed by chromatographic analysis.

  10. Simultaneous determination of codeine and noscapine by flow-injection chemiluminescence method using N-PLS regression.

    Science.gov (United States)

    Rezaei, B; Khayamian, T; Mokhtari, A

    2009-02-20

    A flow injection chemiluminescent (FI-CL) method has been developed for the simultaneous determination of codeine and noscapine using N-PLS regression. The method is based on the fact that kinetic characteristics of codeine and noscapine are different in the Ru(phen)(3)(2+)-Ce(IV) CL system. In flow injection mode, codeine gives broad peak with the highest CL intensity at 4.4s, whereas the maximum CL intensity of the noscapine appears at about 2.6s. Moreover, the effect of increasing H(2)SO(4) concentration was different on the CL intensity of the compounds. An experimental design, central composite design (CCD), was used to realize the optimized variables such as Ru(II) and Ce(IV) concentrations for the both compounds. At the optimized condition, a three-way data structure (samples, H(2)SO(4) concentration, time) was constructed and followed by N-PLS regression. The number of factors for the N-PLS regression was selected based on the minimum values for the root mean squared error of cross validation (RMSECV). The proposed method is applied to the simultaneous quantification of codeine and noscapine in the pharmaceutical preparations.

  11. Enhancement of the analytical properties and catalytic activity of a nickel hexacyanoferrate modified carbon ceramic electrode prepared by two-step sol-gel technique: application to amperometric detection of hydrazine and hydroxyl amine.

    Science.gov (United States)

    Salimi, Abdollah; Abdi, Kamaleddin

    2004-05-28

    The electroless sol-gel technique was used for the construction of nickel hexacyanoferrat (NiHCF) modified carbon composite electrodes (CCEs).This involves two steps: formation of a carbon ceramic electrode fabricated by nickel powder and then immersing the electrode into a sodium- hexacyanoferate solution for the immobilization of NiHCF films. The cyclic voltammety of the resulting modified CCEs prepared under optimum conditions, shows a well defined surface redox couple due to the [Ni(II)Fe(III/II)(CN)(6)](-2/-1) system. The effect of different alkali metal cations in supporting electrolyte on the behavior of the modified electrode were studied. The charge transfer coefficient (alpha) and charge transfer rate constant (k(s)) for modified films were calculated. Hydrazine and hydroxylamine have been chosen as a model to elucidate the electocatalytic ability and analytical parameters of NiHCF modified CCE prepared by one and two-step sol-gel techniques and these compounds determined amperometically at the surface of modified electrodes. The latter shows a good electocatalytic activity towards the oxidation of hydrazine and hydroxylamine in the pH range 3-8 in comparison with CCEs modified by homogeneous mixture of graphite powder, Ni(NO(3))(2) and Na(2)[Fe(CN)(6)], (one-step sol-gel technique). Furthermore, the catalytic rate constant, linear dynamic range, limit of detection, and sensitivity for hydrazine and hydroxylamine detections were evaluated and compared with CCEs prepared with one-step sol-gel method. The modified CCEs containing NiHCF shows good repeatability, short response time, t 90%<3s, long term stability (3 months) and excellent catalytic activity. Furthermore, the method of preparation is rapid and simple and the modified electrodes are renewed by simple mechanical polishing and immersing in [Na(3)Fe(CN](6)] solution.

  12. Planar Amperometric Glucose Sensor Based on Glucose Oxidase Immobilized by Chitosan Film on Prussian Blue Layer

    Directory of Open Access Journals (Sweden)

    Zongyou Chen

    2002-04-01

    Full Text Available A planar amperometric glucose microsensor based on glucose oxidase immobilized by chitosan film on Prussian Blue layer has been developed. The experimental results show that the optimum detection potential is 50 mV (versus Ag/AgCl and the optimum pH is 6.5. Under the selective conditions the sensor exhibits excellent sensitivity of 98 nA/M and a linear range of 0.1-6.0 mM. The apparent Michanelis-Menten constant of the sensor is 21 mM. The response time is less than 60 seconds. No apparent change in the response to glucose was observed during one month. Foremost, the interference of ascorbic and uric acids can be avoided due to selective permeability of chitosan film and electrocatalysis of PB layer to H2O2. The sensor has been applied to detect glucose in human blood serum.

  13. Method for the quantification of vanadyl porphyrins in fractions of crude oils by High Performance Liquid Chromatography-Flow Injection-Inductively Coupled Plasma Mass Spectrometry

    Science.gov (United States)

    Wandekoken, Flávia G.; Duyck, Christiane B.; Fonseca, Teresa C. O.; Saint'Pierre, Tatiana D.

    2016-05-01

    High performance liquid chromatography hyphenated by flow injection to inductively coupled plasma mass spectrometry (HPLC-FI-ICP-MS) was used to investigate V linked to porphyrins present in fractions of crude oil. First, the crude oil sample was submitted to fractionation by preparative liquid chromatography with UV detection, at the porphyrin Soret band wavelength (400 nm). The obtained porphyrin fractions were then separated in a 250 mm single column, in the HPLC, and eluted with different mobile phases (methanol or methanol:toluene (80:20; v:v)). The quantification of V-porphyrins in the fractions eluted from HPLC was carried out by online measuring the 51V isotope in the ICP-MS, against vanadyl octaethylporphine standard solutions (VO-OEP), prepared in the same solvent as the mobile phase, and injected post-column directly into the plasma. A 20 μg L- 1 Ge in methanol was used as internal standard for minimizing non-spectral interference, such as short-term variations due to injection. The mathematical treatment of the signal based on Fast Fourier Transform smoothing algorithm was employed to improve the precision. The concentrations of V as V-porphyrins were between 2.7 and 11 mg kg- 1 in the fractions, which were close to the total concentration of V in the porphyrin fractions of the studied crude oil.

  14. CuO nanosheets-enhanced flow-injection chemiluminescence system for determination of vancomycin in water, pharmaceutical and human serum

    Science.gov (United States)

    Khataee, A. R.; Hasanzadeh, A.; Iranifam, M.; Fathinia, M.; Hanifehpour, Y.; Joo, S. W.

    2014-03-01

    A novel, rapid and sensitive CuO nanosheets (NSs) amplified flow-injection chemiluminescence (CL) system, luminol-H2O2-CuO nanosheets, was developed for determination of the vancomycin hydrochloride for the first time. It was found that vancomycin could efficiently inhibit the CL intensity of luminol-H2O2-CuO nanosheets system in alkaline medium. Under the optimum conditions, the inhibited CL intensity was linearly proportional to the concentration of vancomycin over the ranges of 0.5-18.0 and 18.0-40.0 mg L-1, with a detection limit (3σ) of 0.1 mg L-1. The precision was calculated by analyzing samples containing 5.0 mg L-1 vancomycin (n = 11) and the relative standard deviation (RSD) was 2.8%. Also, a high injection throughput of 120 sample h-1 was obtained. The CuO nanosheets were synthesized by a sonochemical method. Also, X-ray diffraction (XRD) and scanning electron microscopy (SEM) analyses were employed to characterize the CuO nanosheets. The method was successfully employed to determine vancomycin hydrochloride in environmental water samples, pharmaceutical formulation and spiked human serum.

  15. Preconcentration and determination of iron and copper in spice samples by cloud point extraction and flow injection flame atomic absorption spectrometry

    Energy Technology Data Exchange (ETDEWEB)

    Sahin, Cigdem Arpa, E-mail: carpa@hacettepe.edu.tr [Hacettepe University, Chemistry Department, 06800 Beytepe, Ankara (Turkey); Tokgoez, Ilknur; Bektas, Sema [Hacettepe University, Chemistry Department, 06800 Beytepe, Ankara (Turkey)

    2010-09-15

    A flow injection (FI) cloud point extraction (CPE) method for the determination of iron and copper by flame atomic absorption spectrometer (FAAS) has been improved. The analytes were complexed with 3-amino-7-dimethylamino-2-methylphenazine (Neutral Red, NR) and octylphenoxypolyethoxyethanol (Triton X-114) was added as a surfactant. The micellar solution was heated above 50 {sup o}C and loaded through a column packed with cotton for phase separation. Then the surfactant-rich phase was eluted using 0.05 mol L{sup -1} H{sub 2}SO{sub 4} and the analytes were determined by FAAS. Chemical and flow variables influencing the instrumental and extraction conditions were optimized. Under optimized conditions for 25 mL of preconcentrated solution, the enrichment factors were 98 and 69, the limits of detection (3s) were 0.7 and 0.3 ng mL{sup -1}, the limits of quantification (10s) were 2.2 and 1.0 ng mL{sup -1} for iron and copper, respectively. The relative standard deviation (RSD) for ten replicate measurements of 10 ng mL{sup -1} iron and copper were 2.1% and 1.8%, respectively. The proposed method was successfully applied to determination of iron and copper in spice samples.

  16. Ultrasound-assisted dispersive liquid-liquid microextraction of tetracycline drugs from egg supplements before flow injection analysis coupled to a liquid waveguide capillary cell.

    Science.gov (United States)

    Rodríguez, Michael Pérez; Pezza, Helena Redigolo; Pezza, Leonardo

    2016-09-01

    A simple, rapid, and efficient ultrasound-assisted dispersive liquid-liquid microextraction (US-DLLME) method was developed for extraction of tetracycline residues from egg supplement samples, with subsequent determination by flow injection analysis (FIA) coupled to a liquid waveguide capillary cell (LWCC) and a controlled temperature heating bath. Tetracyclines react with diazotized p-sulfanilic acid, in a slightly alkaline medium, to form azo compounds that can be measured at 435 nm. The reaction sensitivity improved substantially (5.12-fold) using an in-line heating temperature of 45 °C. Multivariate methodology was used to optimize the factors affecting the extraction efficiency, considering the volumes of extraction and disperser solvents, sonication time, extraction time, and centrifugation time. Good linearity in the range 30-600 μg L(-1) was obtained for all the tetracyclines, with regression coefficients (r) higher than 0.9974. The limits of detection ranged from 6.4 to 11.1 μg L(-1), and the recoveries were in the range 85.7-96.4 %, with relative standard deviation lower than 9.8 %. Analyte recovery was improved by approximately 6 % when the microextraction was assisted by ultrasound. The results obtained with the proposed US-DLLME-FIA method were confirmed by a reference HPLC method and showed that the egg supplement samples analyzed were suitable for human consumption.

  17. Focused-microwave-assisted reaction in flow injection spectrophotometry: a new liquid-vapor separation chamber for determination of reducing sugars in wine.

    Science.gov (United States)

    Oliveira, A F; Fatibello-Filho, O; Nóbrega, J A

    2001-10-31

    The usefulness of an unsegmented liquid/vapor phases flow injection system for determining reducing sugars in wines using a focalized poly(tetrafluoroethylene) (PTFE) coiled reactor positioned at the output antenna of a domestic microwave oven at 700 W is demonstrated. In this system, sample or reference solution is mixed to 2.5 mol l(-1) sodium hydroxide and 6.8 mmol l(-1) potassium hexacyanoferrate(III) solutions previously merged in a confluence point and the reducing sugars (glucose plus fructose) were oxidized by potassium hexacyanoferrate(III) solution into the PTFE coiled reactor positioned in the microwave oven cavity. After phases separation at a proposed separation chamber (SC), the decrease of K(3)Fe(CN)(6) concentration in the liquid phase was measured at 420 nm. Using this SC, a favorable dispersion profile and a decrease of hydrodynamic pressure were observed. The flow procedure presented similar sensitivities to glucose and fructose in the experimental conditions adopted, allowing the determination of the reducing sugars content (fructose plus glucose concentrations) in the concentration range from 40 to 400 mumol l(-1) with a detection limit of 9 mumol l(-1). The RSD was 1.9% for a 120 mumol l(-1) fructose solution (n=12) and the analytical frequency was 54 h(-1). The results obtained for reducing sugars in several wines using the proposed flow system and those obtained using the Somogyi-Nelson batch procedure were in agreement at the 95% confidence level.

  18. A novel solidified floating organic drop microextraction method for preconcentration and determination of copper ions by flow injection flame atomic absorption spectrometry in water samples

    Directory of Open Access Journals (Sweden)

    Arpa Şahin Ç.

    2013-04-01

    Full Text Available A simple, rapid and inexpensive solidified floating organic drop microextraction (SFODME and flow injection flame atomic absorption spectrometric determination (FI-FAAS method for copper was developed. 3-amino-7-dimethylamino-2-methylphenazine (Neutral red, NR was used as the complexing agent. Several factors affecting the microextraction efficiency, such as, pH, NR and sodium dodecylbenzenesulfonate (SDBS concentration, extraction time, stirring rate, and temperature were investigated and optimized. Under optimized experimental conditions an enrichment factor of 541 was obtained for 100 mL of sample solution. The calibration graph was linear in the range of 0.5 – 20.0 ng mL–1 and the limit of detection (3s was 0.18 ng mL–1, the limit of quantification (10s was 0.58 ng mL–1. The relative standard deviation (RSD for 10 replicate measurements of 10 ng mL–1 copper was 2.7%. The developed method was successfully applied to the extraction and determination of copper in different certified reference materials (Estuarine water, Slew 3 and fortified water, TM 23.2 and real water samples and satisfactory results were obtained.

  19. Study on the Flow Injection Micro-Column Pre-Separation System Coupled With High Performance Liquid Chromatography for the Determination of Ecdysterone in Traditional Chinese Medicine

    Institute of Scientific and Technical Information of China (English)

    2000-01-01

    A flow injection (FI) micro-column system coupled with high performance liquid chromatography (HPLC) was proposed for the pre-separation and determination of active organic component (ecdysterone) in traditional Chinese medicine, Loulu. The factors influencing separation performance were investigated and optimized. Under the optimal conditions, the contents of ecdysterone in Loulu were determined by HPLC system using MeOH-H20 (40 : 60,V/V) as the mobile phase at a flow rate of 1.0 mL/min. The calibration curve was linear in the range of 0. 5~100 mg/L of ecdysterone concentrations. The detection limit of the analyte was 0. 11 μmoi/L(3σ) with a precision of 0. 38% RSD (n=7, c=10. 0 mg/L). The average recovery of the method was 98.7%. The proposed method has been applied to determine ecdysterone in practical samples, and the determined values by both external standard method and standard addition method were in good agreement. Compared to the traditional solid extraction method, the system proposed has the advantages of simple procedure, good reproducibility, minimum volume requirement, reduction of matrix interference and iow contamination risk.

  20. A flow injection chemiluminescence method for the determination of lincomycin in serum using a diperiodato-cuprate (III)-luminol system.

    Science.gov (United States)

    Hu, Yufei; Li, Gongke; Zhang, Zhujun

    2011-01-01

    In this paper, the novel trivalent copper-periodate complex {K₅[Cu(HIO₆)₂], DPC} has been applied in a luminol-based chemiluminescence (CL) reaction. Coupled with flow injection (FI) technology, the FI-CL method was proposed for the determination of lincomycin hydrochloride. The CL reaction between luminol and DPC occurred in an alkaline medium. The CL intensity could be greatly enhanced by lincomycin hydrochloride. The relative CL intensity was proportional to the concentration of lincomycin hydrochloride in the range of 1 × 10⁻⁸ to 5 × 10⁻⁶ g mL⁻¹ and the detection limit was at the 3.5 × 10⁻⁹ g mL⁻¹ level. The relative standard deviation at 5 × 10⁻⁸ g mL⁻¹ was 1.7% (n = 9). The sensitive method was successfully applied to the direct determination of lincomycin hydrochloride (ng mL⁻¹) in serum. A possible mechanism of the lumonol-DPC CL reaction was discussed by the study of the CL kinetic characteristics and the spectra of CL reaction. The oxidability of DPC was studied by means of its electrochemical response.

  1. In-line electrochemical reagent generation coupled to a flow injection biamperometric system for the determination of sulfite in beverage samples.

    Science.gov (United States)

    de Paula, Nattany T G; Barbosa, Elaine M O; da Silva, Paulo A B; de Souza, Gustavo C S; Nascimento, Valberes B; Lavorante, André F

    2016-07-15

    This work reports an in-line electrochemical reagent generation coupled to a flow injection biamperometric procedure for the determination of SO3(2-). The method was based on a redox reaction between the I3(-) and SO3(2-) ions, after the diffusion of SO2 through a gas diffusion chamber. Under optimum experimental conditions, a linear response ranging from 1.0 to 12.0 mg L(-1) (R=0.9999 and n=7), a detection and quantification limit estimated at 0.26 and 0.86 mg L(-1), respectively, a standard deviation relative of 0.4% (n=10) for a reference solution of 4.0 mg L(-1) SO3(2-) and sampling throughput for 40 determinations per hour were achieved. Addition and recovery tests with juice and wine samples were performed resulting in a range between 92% and 110%. There were no significant differences at a 95% confidence level in the analysis of eight samples when comparing the new method with a reference procedure.

  2. An on-line spectrophotometric determination of trace amounts of thiourea in tap water, orange juice, and orange peel samples using multi-channel flow injection analysis.

    Science.gov (United States)

    Arab Chamjangali, M; Goudarzi, N; Ghochani Moghadam, A; Amin, A H

    2015-01-01

    In this work, a flow injection analysis (FIA) method was introduced for the determination of trace amounts of thiourea in tap water. This method is based upon the inhibition effect of thiourea on the reaction between meta-cresol purple (MCP) and potassium bromate catalyzed by bromide ions in a sulfuric acid medium. In the presence of thiourea, an induction period appears in the reaction system, and as a result, the absorbance of MCP increases at 525 nm in the FIA manifold. The chemical and FIA variables are studied and optimized using the univariate and Simplex optimization methods. Under the optimum conditions, thiourea can be determined in the range of 0.100-13.0 μg mL(-1). The limit of detection (3σ) for thiourea was found to be 0.0310 μg mL(-1). The relative standard deviations (RSDs) for six replicate determinations of 0.500, 5.00, and 12.0 μg mL(-1) of thiourea were 4.0%, 1.8%, and 1.2%, respectively. The proposed method was also applied for the determination of thiourea in orange juice and orange peel samples with recoveries in the range of 98.0-101%. The analytical speed of the method was calculated to be about 120 sample per hour.

  3. A novel flow-injection method for the determination of Pt(IV) in environmental samples based on chemiluminescence reaction of lucigenin and biosorption.

    Science.gov (United States)

    Malejko, Julita; Godlewska-Zyłkiewicz, Beata; Kojło, Anatol

    2010-06-15

    A new flow-injection chemiluminescence method (FI-CL) was developed for the determination of trace amounts of Pt(IV). The method is based on the quenching effect of the analyte on CL emission generated by lucigenin in alkaline solution. Application of a column filled with an algae Chlorella vulgaris immobilized on Cellex-T resin allowed to preconcentrate and separate the Pt(IV) ions from complex environmental samples, such as road dust. The developed method is simple and does not require sophisticated instrumentation. It is also characterized by a very low limit of detection (0.1ngmL(-1)), good sensitivity and precision (RSD<3%). The accuracy of the presented method was confirmed by analysis of a certified reference material of tunnel dust (BCR-723). The content of Pt in road dust samples collected in Białystok (Poland) in 2009 determined by the evaluated method was 351.8+/-54.6ngg(-1) and was higher than in samples collected in years 2000 and 2003.

  4. A rapid and accurate method for determining protein content in dairy products based on asynchronous-injection alternating merging zone flow-injection spectrophotometry.

    Science.gov (United States)

    Liang, Qin-Qin; Li, Yong-Sheng

    2013-12-01

    An accurate and rapid method and a system to determine protein content using asynchronous-injection alternating merging zone flow-injection spectrophotometry based on reaction between coomassie brilliant blue G250 (CBBG) and protein was established. Main merit of our approach is that it can avoid interferences of other nitric-compounds in samples, such as melamine and urea. Optimized conditions are as follows: Concentrations of CBBG, polyvinyl alcohol (PVA), NaCl and HCl are 150 mg/l, 30 mg/l, 0.1 mol/l and 1.0% (v/v), respectively; volumes of the sample and reagent are 150 μl and 30 μl, respectively; length of a reaction coil is 200 cm; total flow rate is 2.65 ml/min. The linear range of the method is 0.5-15 mg/l (BSA), its detection limit is 0.05 mg/l, relative standard deviation is less than 1.87% (n=11), and analytical speed is 60 samples per hour.

  5. Preparation of a new Cd(II)-imprinted polymer and its application to determination of cadmium(II) via flow-injection-flame atomic absorption spectrometry.

    Science.gov (United States)

    Gawin, Marta; Konefał, Jadwiga; Trzewik, Bartosz; Walas, Stanisław; Tobiasz, Anna; Mrowiec, Halina; Witek, Ewa

    2010-01-15

    A new cadmium(II)-imprinted polymer based on cadmium(II) 2,2'-{ethane-1,2-diylbis[nitrilo(E)methylylidene]} diphenolate-4-vinylpyridine complex was obtained via suspension polymerization. The beads were used as a minicolumn packing for flow-injection-flame atomic absorption spectrometry (FI-FAAS) determination of cadmium(II) in water samples. Sorption effectiveness was optimal within pH range of 6.6-7.7. Nitric acid, 0.5% (v/v) was used as eluent. Fast cadmium(II) sorption by the proposed material enabled to apply sample flow rates up to 10mLmin(-1) without loss in sorption effectiveness. Enrichment factor (EF), concentration efficiency (CE) and limit of detection (LOD, 3sigma) found for 120-s sorption time were 117, 39.1min(-1) and 0.11microgL(-1), respectively. Sorbent stability was proved for at least 100 preconcentration cycles (RSD=2.9%). When compared to non-imprinted polymer the new Cd(II)-imprinted polymer exhibited improved selectivity towards cadmium(II) against other heavy metal ions, especially Cu(II) and Pb(II), as well as light metal ions. Accuracy of the method was tested for ground water and waste water certified reference materials and fortified water. The method was applied to Cd(II) determination in natural water samples.

  6. Trace mercury determination in drinking and natural water samples by room temperature ionic liquid based-preconcentration and flow injection-cold vapor atomic absorption spectrometry

    Energy Technology Data Exchange (ETDEWEB)

    Martinis, Estefania M.; Berton, Paula [Laboratory of Environmental Research and Services of Mendoza (LISAMEN), (CCT - CONICET - Mendoza), Av. Ruiz Leal S/N Parque General San Martin, CC. 131, M 5502 IRA Mendoza (Argentina); Olsina, Roberto A. [INQUISAL-CONICET, Departamento de Quimica Analitica, Facultad de Quimica, Bioquimica y Farmacia, Universidad Nacional de San Luis, San Luis (Argentina); Altamirano, Jorgelina C. [Laboratory of Environmental Research and Services of Mendoza (LISAMEN), (CCT - CONICET - Mendoza), Av. Ruiz Leal S/N Parque General San Martin, CC. 131, M 5502 IRA Mendoza (Argentina); Instituto de Ciencias Basicas, Universidad Nacional de Cuyo, Mendoza (Argentina); Wuilloud, Rodolfo G., E-mail: rwuilloud@lab.cricyt.edu.ar [Laboratory of Environmental Research and Services of Mendoza (LISAMEN), (CCT - CONICET - Mendoza), Av. Ruiz Leal S/N Parque General San Martin, CC. 131, M 5502 IRA Mendoza (Argentina); Instituto de Ciencias Basicas, Universidad Nacional de Cuyo, Mendoza (Argentina)

    2009-08-15

    A liquid-liquid extraction procedure (L-L) based on room temperature ionic liquid (RTIL) was developed for the preconcentration and determination of mercury in different water samples. The analyte was quantitatively extracted with 1-butyl-3-methylimidazolium hexafluorophosphate ([C{sub 4}mim][PF{sub 6}]) under the form of Hg-2-(5-bromo-2-pyridylazo)-5-diethylaminophenol (Hg-5-Br-PADAP) complex. A volume of 500 {mu}l of 9.0 mol L{sup -1} hydrochloric acid was used to back-extract the analyte from the RTIL phase into an aqueous media prior to its analysis by flow injection-cold vapor atomic absorption spectrometry (FI-CV-AAS). A preconcentration factor of 36 was achieved upon preconcentration of 20 mL of sample. The limit of detection (LOD) obtained under the optimal conditions was 2.3 ng L{sup -1} and the relative standard deviation (RSD) for 10 replicates at 1 {mu}g L{sup -1} Hg{sup 2+} was 2.8%, calculated with peaks height. The method was successfully applied to the determination of mercury in river, sea, mineral and tap water samples and a certified reference material (CRM).

  7. Univariate and simplex optimization for the flow-injection spectrophotometric determination of copper using nitroso-R salt as a complexing agent.

    Science.gov (United States)

    Purachat, B; Liawruangrath, S; Sooksamiti, P; Rattanaphani, S; Buddhasukh, D

    2001-03-01

    A simple colorimetric flow-injection system for the determination of Cu(II) based on a complexation reaction with nitroso-R salt is described. The chemical and FIA variables were established using the univariate and simplex methods. A small volume of Cu(II) was mixed with merged streams of nitroso-R salt and acetate buffer solutions. The absorbance of the complex was continuously monitored at 492 nm. The calibration curve over the concentration range 1.0-7.0 microg ml(-1) was obtained. The relative standard deviation for determining 4.0 microg ml(-1) Cu(II) was 0.47% (n = 11). The detection limit (3sigma) was 0.68 microg ml(-1) and the sample throughput was 150 h(-1). The validity of the method has been satisfactorily examined for the determination of Cu(II) in wastewater and copper ore samples. The accuracy was found to be high, because the student t-values were calculated to be less than the theoretical values when the results were compared with those obtained by FAAS.

  8. On-line flow-injection liquid-phase microextraction and spectrophotometric determination of traces of copper(II) with trithia-9-crown-3 as complexing agent.

    Science.gov (United States)

    Zahedi, Mir Mahdi; Shamsipur, Mojtaba; Pourmortazavi, Seied Mahdi

    2013-01-01

    A novel on-line flow-injection liquid-phase microextraction (FI-LPME) and spectrophotometric determination of the Cu(2+) ion using trithia-9-crown-3 (TT9C3) as a sensitive and selective charge transfer complexing agent was developed. After phase segmentation by pulsating motions of a peristaltic pump, the phase separation takes place by the aid of gravitation forces. The optimum values of the pH (= 5 of phosphate buffer) and ionic strength (5 mM Na2SO4) of the solution, amount of ligand (2.0 × 10(-3) mol L(-1)), nature of the counter ion (10 mM SDS), volume of the organic solvent (150 μL), coil length (3 m) and extraction time (2 min) for an efficient extraction were determined. The calibration curve was found to be linear over a concentration range of 0.008 - 4.2 μg mL(-1) (R(2) = 0.9985) with a limit of detection of 0.37 ng mL(-1). The enrichment factor and relative standard deviation (n = 7) were 16 and 5.7%, respectively. Finally, the proposed method was applied to the determination of copper(II) as an impurity in the several commercial metallic salts.

  9. Field sample preconcentration of copper in sea water using chelating minicolumns subsequently incorporated on a flow-injection-flame atomic absorption spectrometry system.

    Science.gov (United States)

    Yebra, M C; Carro, N; Enríquez, M F; Moreno-Cid, A; García, A

    2001-06-01

    A field flow preconcentration system for copper determination in seawater is described. Seawater samples are collected and preconcentrated in situ by passing them using a peristaltic pump through a minicolumn packed with Amberlite XAD-4 impregnated with the complexing agent 1-(2-pyridylazo)-2-naphthol. Thus, copper is preconcentrated without the interference of the saline matrix. Once in the laboratory, the minicolumns loaded with copper are incorporated on a flow injection system and eluted with a small volume of a 20% (v/v) ethanolic solution of 0.5 mol L-1 hydrochloric acid into the nebuliser-burner system of a flame atomic absorption spectrometer. The analytical figures of merit for the determination of copper are as follows: detection limit (3s), 0.06 microgram L-1; precision (RSD), 1.2% for 2 micrograms L-1; enrichment factor, 30 (using 25 mL of sample and 83 microL of eluent). Analysis of certified reference materials (SLEW-3 and NASS-5) showed good agreement with the certified value. This procedure was applied to the determination of copper in seawater samples from Galicia (Spain).

  10. Determination of ammonium in Kjeldahl digests by gas-diffusion flow-injection analysis with a bulk acoustic wave-impedance sensor.

    Science.gov (United States)

    Su, X L; Nie, L H; Yao, S Z

    1997-11-01

    A novel flow-injection analysis (FIA) system has been developed for the rapid and direct determination of ammonium in Kjeldahl digests. The method is based on diffusion of ammonia across a PTFE gas-permeable membrane from an alkaline (NaOH/EDTA) stream into a stream of diluted boric acid. The trapped ammonium in the acceptor is determined on line by a bulk acoustic wave (BAW)-impedance sensor and the signal is proportional to the ammonium concentration present in the digests. The proposed system exhibits a favorable frequency response to 5.0 x 10(-6)-4.0 x 10(-3) mol l(-1) ammonium with a detection limit of 1.0 x 10(-6) mol l(-1), and the precision was better than 1% (RSD) for 0.025-1.0 mM ammonium at a through-put of 45-50 samples h(-1). Results obtained for nitrogen determination in amino acids and for proteins determination in blood products are in good agreement with those obtained by the conventional distillation/titration method, respectively. The effects of composition of acceptor stream, cell constant of conductivity electrode, sample volume, flow rates and potential interferents on the FIA signals were discussed in detail.

  11. Rapid determination of zinc and iron in foods by flow-injection analysis with flame atomic-absorption spectrophotometry and slurry nebulization.

    Science.gov (United States)

    de Andrade, J C; Strong, F C; Martin, N J

    1990-07-01

    A rapid method of determining zinc and iron in food by flame atomic-absorption spectrophotometry with slurry nebulization into an air-acetylene flame has been developed. A V-groove, clog-free Babington-type nebulizer, coupled to a single-line flow-injection analysis (FIA) system, was employed to introduce the slurry into the spray chamber. Under the FIA conditions described, an injection frequency of 120/hr is possible, with negligible carry-over and memory effects. The calibration graphs were obtained by using various concentrations (up to 0.1 g/ml) of white bean homogenate as standards, rather than solutions. The method has been applied to various kinds of foods, including grains, vegetables, fruits and sausage. Homogenization of semi-prepared samples to form slurries took only 4 min. Relative deviations between results by the slurry and solution methods for both elements averaged 2-3%. Detection limits by the slurry method were 0.3 mug/ml Zn and 0.6 mug/ml Fe.

  12. Chromium Speciation Using Flow-injection Preconcentration on Xylenol Orange Functionalized Amberlite XAD-16 and Determination in Industrial Water Samples by Flame Atomic Absorption Spectrometry.

    Science.gov (United States)

    Saxena, Reena; Sharma, Niharika; Tiwari, Shelja

    2015-01-01

    A speciation method for Cr(III) and Cr(VI) by on-line solid-phase extraction using a flow-injection system with FAAS has been proposed. The Cr(III) was selectively retained at pH 5 on the AXAD16-XO chelating resin and was eluted using 0.5 mol L(-1) HNO3. The preconcentration factor and the detection limit (3σ) of 73 and 0.11 μg L(-1), respectively, were obtained for a 120-s preconcentration time. The precision (%RSD) at the 100 μg L(-1) level was 1.08%. The linearity for Cr(III) measurements was up to 600 μg L(-1). The total chromium was determined by reducing Cr(VI) to Cr(III) using hydroxylamine hydrochloride, and the Cr(VI) concentration was obtained by subtraction from the total chromium concentration. The effect of interfering ions was examined towards the selectivity of the proposed system for Cr(III). Spike recovery studies in industrial water samples were carried out using standard Cr(III) and Cr(VI) solutions traceable to NIST. The proposed method was validated using SRM 1643e (Trace Elements in Water) supplied by NIST, USA.

  13. Masking Agents Evaluation for Lead Determination by Flow Injection-Hydride Generation-Atomic Fluorescence Spectrometry Technique: Effect of KI, L-Cysteine, and 1,10-Phenanthroline.

    Science.gov (United States)

    Beltrán, Blanca G; Leal, Luz O; Ferrer, Laura; Cerdà, Víctor

    2016-01-01

    Hydride generation (HG) of lead technique presents interferences from foreign ions of complex matrix samples. In order to minimize these interferences, the effect of masking agents such as KI, L-cysteine, and 1,10-phenanthroline was studied in the absence and in the presence of selected interfering species (As, Cr, Cu, and Fe). Different modes of addition of masking agents were accomplished, that is, to either sample or KBH4 reducing solution. The lead determinations were performed using a flow injection analysis (FIA) system coupled to HG and atomic fluorescence spectrometry (AFS). The linearity of calibration curves (1-10 μg Pb L(-1)) was not affected by the addition of the masking agents. The use of KI in the reducing solution diminished interferences from concentrations of As and Cu, while 1,10-phenanthroline showed a positive effect on the interference by As. Moreover, Cr and Cu appeared to be the most serious interfering ions for plumbane (PbH4), because they drastically reduced the analytical signal of lead. Fe did not present any interference under the employed experimental conditions, even at high levels. The accuracy was established through the analysis of certified reference material (i.e., BCR-610, groundwater) using KI as masking agent. The detection limit reached by FIA-HG-AFS proposed methodology was 0.03 μg Pb L(-1).

  14. Development of an Amperometric Biosensor Platform for the Combined Determination of L-Malic, Fumaric, and L-Aspartic Acid.

    Science.gov (United States)

    Röhlen, Désirée L; Pilas, Johanna; Schöning, Michael J; Selmer, Thorsten

    2017-09-02

    Three amperometric biosensors have been developed for the detection of L-malic acid, fumaric acid, and L -aspartic acid, all based on the combination of a malate-specific dehydrogenase (MDH, EC 1.1.1.37) and diaphorase (DIA, EC 1.8.1.4). The stepwise expansion of the malate platform with the enzymes fumarate hydratase (FH, EC 4.2.1.2) and aspartate ammonia-lyase (ASPA, EC 4.3.1.1) resulted in multi-enzyme reaction cascades and, thus, augmentation of the substrate spectrum of the sensors. Electrochemical measurements were carried out in presence of the cofactor β-nicotinamide adenine dinucleotide (NAD(+)) and the redox mediator hexacyanoferrate (III) (HCFIII). The amperometric detection is mediated by oxidation of hexacyanoferrate (II) (HCFII) at an applied potential of + 0.3 V vs. Ag/AgCl. For each biosensor, optimum working conditions were defined by adjustment of cofactor concentrations, buffer pH, and immobilization procedure. Under these improved conditions, amperometric responses were linear up to 3.0 mM for L-malate and fumarate, respectively, with a corresponding sensitivity of 0.7 μA mM(-1) (L-malate biosensor) and 0.4 μA mM(-1) (fumarate biosensor). The L-aspartate detection system displayed a linear range of 1.0-10.0 mM with a sensitivity of 0.09 μA mM(-1). The sensor characteristics suggest that the developed platform provides a promising method for the detection and differentiation of the three substrates.

  15. New Trends in Flow Injection Analysis: Exploitation of Sequential and Lab-on-Valve Schemes

    DEFF Research Database (Denmark)

    Hansen, Elo Harald

    which are difficult or, in fact, otherwise impossible to do, thereby opening new and novel avenues for analytical methods relying on concepts such as kinetic discriminations schemes, exploitation of metastable constituents of attractive analytical characteristics, or utilisation of detection by bio...... has appeared, that is, the Lab-on-Valve (LOV) approach, the conceptual basis of which is to incorporate all the necessary unit operational manipulations required, and, when possible, even the detection device into a single small integrated microconduit, or “laboratory”, placed atop a selection valve...

  16. Flow-injection sample preconcentration for ion-pair chromatography of trace metals in waters.

    Science.gov (United States)

    Pobozy, Ewa; Halko, Radoslav; Krasowski, Marcin; Wierzbicki, Tomasz; Trojanowicz, Marek

    2003-05-01

    Selected trace transition metal ions have been determined in an FIA/HPLC hyphenated system using on-line preconcentration on cellulose functionalised sorbent Cellex P. For HPLC separation ion-pair chromatography was employed with spectrophotometric detection at 510 nm using post-column derivatisation with PAR. Favourable kinetic conditions of sorption and elution as well as optimisation of hyphenated system allowed to obtain detection limits at sub-microgL(-1) level at 25 min preconcentration time. The developed method was employed for determination of Co(II), Ni(II), Cd(II) and Mn(II) in river water with reasonable agreement of obtained results with electrothermal AAS determination.

  17. 高效阴离子交换色谱-脉冲安培法检测低聚异麦芽糖%Determination of Isomaltooligosaccharides by High Performance Anion Exchange Chromatography Coupled with Pulsed Amperometric Detection (HPAEC-PAD)

    Institute of Scientific and Technical Information of China (English)

    张晓萍; 段钢

    2012-01-01

    建立了高效阴离子交换色谱-脉冲安培检测法定量分析低聚异麦芽糖的方法。采用Carbo PakTM PA10色谱柱,配合安培检测器,以NaOH及醋酸钠为洗脱剂。采用此方法不仅一次性实现了低聚异麦芽糖常规组分中葡萄糖、麦芽糖、麦芽三糖、异麦芽糖、异麦芽三糖,潘糖的有效分离,也实现了异麦芽四糖、异麦芽五糖、异麦芽六糖、异麦芽七糖、海藻糖、麦芽酮糖、曲二糖、黑曲霉糖高聚合度糖及二糖同分异构体间的分离及检测。以不同浓度的标准糖混合溶液建立了校正曲线,此方法中,各组分在0.032~25.975mg/L间具有良好的线性关系,各物质的检测限和定量限分别在0.008~0.022mg/L和0.027—0.073mg/L,样品加标回收率为82.02%~116.37%。%A one-step method for quantitatively determination of isomahooligosaccharides (IMO) was developed using high performance anion exchange chromatography coupled with pulsed amperometric detection (HPAEC-PAD). The method was built on a CarboPakTM PAl0 column using NaOH and NaAC as eluents. Using this method, besides conventional components of isomahose, isomaltotriose, panose and some saccharides with higher DP were identified from IMO syrup, other transglycosylation saccharides such as trehalose, kojibiose, nigerose and maltulose were also detected from the syrup. Calibration was carried out by dissolving 15 kinds of standard samples containing glucose, fructose, maltose, maltotriose, isomaltose, isomaltotriose, isomaltotetraose, isomaltopentaose, isomaltohexaose, iso- maltoheptaose, panose, trehalose, maltulose, kojibiose, and nigerose into a mixed solution. The standard solution was diluted to a calibration range from 0. 032 to 25. 975 mg/L. The calibration curves showed good linearity of IMO within this range. The detection limits (LODs) and the quatification limits (LQD) were 0. 008 - 0. 022 mg/L and 0. 027 -0

  18. Flow-injection potentiometry by poly(vinyl chloride)-membrane electrodes with diphosphoryl-dicarboxylicacid-p-tert-butylcalix[4]arene ionophore for the determination of Th(IV) ions.

    Science.gov (United States)

    Mizani, Farhang; Shamsipur, Mojtaba; Yaftian, Mohammad R; Matt, Dominique

    2013-01-01

    A new coated ion-selective electrode for the determination of trace thorium ions by flow-injection potentiometry (FIP) has been developed. A poly(vinyl chloride) (PVC)-based membrane was coated on a graphite electrode. The optimum membrane contained 5 wt% diphosphoryl-dicarboxylicacid-p-tert-butylcalix[4]arene (L) as the ionophore, 59 wt% dioctyl phthalate (DOP), 33 wt% PVC and 3 wt% additive sodium tetraphenylborate. The response was linear from 2.0 × 10(-7) to 1.0 × 10(-2) M with a slope of 13.9 mV decade(-1) and a limit of detection of 9.0 × 10(-8) M. The pH-independent region ranged from 3.15 to 6.5, and the lifetime was longer than 8 weeks when used in the flow injection analysis (FIA) system. Selectivity coefficients for several ions were obtained by the separate solutions method. Results showed that, for all cations used, the selectivity coefficients were in the order of 10(-3), or smaller. The flow cell is simple to construct and free from memory effect problems over long periods of use. The proposed sensor was successfully applied to the direct determination of thorium in both real and synthetic samples.

  19. Indirect flow injection determination of N-acetyl-L-cysteine using cerium(IV) and ferroin; Determinacao indireta de N-acetil-L-cisteina por injecao em fluxo empregando Ce(IV) e ferroina

    Energy Technology Data Exchange (ETDEWEB)

    Vieira, Heberth Juliano; Fatibello-Filho, Orlando [Sao Carlos Univ., SP (Brazil). Dept. de Quimica]. E-mail: bello@dq.ufscar.br

    2005-09-15

    An indirect flow injection spectrophotometric procedure is proposed for the determination of N-acetyl-L-cysteine in pharmaceutical formulations. In this system, ferroin ([Fe(II)-(fen){sub 2}]{sup 2+}) in excess, with a strong absorption at 500 nm, is oxidized by cerium(IV) yielding cerium(III) and [Fe(III)-(fen){sub 2}]{sup 3+} (colorless), thus producing a baseline. When N-acetyl-L-cysteine solution is introduced into the flow injection system, it reacts with cerium(IV) increasing the analytical signal in proportion to the drug concentration. Under optimal experimental conditions, the linearity of the analytical curve for N-acetyl-L-cysteine ranged from 6.5x10{sup -6} to 1.3x10{sup -4} mol L{sup -1}. The detection limit was 5.0x10{sup -6} mol L{sup -1}and recoveries between 98.0 and 106% were obtained. The sampling frequency was 60 determinations per hour and the RSD was smaller than 1.4% for 2.2x10{sup -5} mol L{sup -1} N-acetyl-L-cysteine. (author)

  20. Chemiluminescence determination of cefotaxime sodium with flow-injection analysis of cerium (IV)-rhodamine 6G system and its application to the binding study of cefotaxime sodium to protein with on-line microdialysis sampling

    Science.gov (United States)

    Chen, Dinglong; Wang, Huiying; Zhang, Zhujun; Ci, Lijie; Zhang, Xuehong

    2011-01-01

    A simple, sensitive and rapid flow-injection chemiluminescence (CL) method has been developed for the determination of cefotaxime sodium based on the chemiluminescence reaction of cefotaxime sodium with ceric sulfate and rhodamine 6G in nitric acid solution. The concentration of cefotaxime sodium was proportional with the CL intensity in the range of 4 × 10 -8 - 8 × 10 -6 mol L -1. The detection limit (signal-to-noise ratio = 3) was 1 × 10 -8 mol L -1. Coupled to the technique of on-line microdialysis sampling, this method was successfully applied to study cefotaxime sodium-protein interaction. The drug and protein were mixed in different molar ratios in Ringer's solution, pH 7.4, and incubated at 37 °C in a water bath. The microdialysis probe was utilized to sample the mixed solution at a perfusion rate of 5 μL min -1 and the recovery of cefotaxime sodium under experimental condition was 16.2%. The data obtained by the present Microdialysis-Flow Injection Analysis-CL method was analyzed with the Scatchard analysis and Klotz plot. The estimated association constant ( K) and the number of the binding sites ( n) on one of BSA molecule were 5.94 × 10 4 M -1 and 1.29 (Klotz equation), respectively.

  1. Extractable sulphate-sulphur, total sulphur and trace-element determinations in plant material by flow injection analysis

    Energy Technology Data Exchange (ETDEWEB)

    Heanes, D.L. (South Australian Department of Agriculture, Adelaide (Australia))

    1990-01-01

    A rapid, accurate and reproducible procedure for determining total sulphur(S) and trace elements (copper, zinc, manganese and iron) in plant material is described. Plant material is digested in culture tubes with a mixture of nitric and perchloric acids containing ammonium metavanadate and calcium chloride. In the acid digest, concentrations of total-S as sulphate are determined by turbidimetry and trace-elements by flame atomic absorption spectrophotometry using flow injection analysis. The results for a range of plant materials compare well with those obtained by conventional procedures for the same elements. The microprocessor controlled digestion and multielement assay procedure described here offers improved laboratory efficiencies in materials, time and cost effectiveness. The techniques should be particularly useful when plant tissues are in limited supply.

  2. Flow Injection Analysis of Mercury Using 4-(Dimethylamino Benzaldehyde-4-Ethylthiosemicarbazone as the Ionophore of a Coated Wire Electrode

    Directory of Open Access Journals (Sweden)

    Sulaiman Ab Ghani

    2012-11-01

    Full Text Available A flow injection analysis (FIA incorporating a thiosemicarbazone-based coated wire electrode (CWE was developed method for the determination of mercury(II. A 0.1 M KNO3 carrier stream with pH between 1 and 5 and flow rate of 1 mL·min−1 were used as optimum parameters. A linear plot within the concentration range of 5 × 10−6–0.1 M Hg(II, slope of 27.8 ± 1 mV per decade and correlation coefficient (R2 of 0.984 were obtained. The system was successfully applied for the determination of mercury(II in dental amalgam solutions and spiked environmental water samples. Highly reproducible measurements with relative standard deviation (RSD < 1% (n = 3 were obtained, giving a typical throughput of 30 samples·h−1.

  3. A novel flow injection spectrophotometric method using plant extracts as green reagent for the determination of doxycycline

    Science.gov (United States)

    Palamy, Sysay; Ruengsitagoon, Wirat

    2017-01-01

    A novel flow injection spectrophotometric method was developed for the determination of doxycycline in pharmaceutical preparations using iron(III) contained in extracts from plants. The assay was based on the complex formed between doxycycline and iron(III) characterized by an absorption maximum at 435 nm. The calibration graphs obtained over the doxycycline concentration range 5-250 μg mL- 1 gave correlation coefficients of 0.9979, 0.9987 and 0.9987 with the three green reagents prepared from Senna alata (L.) Roxb. (S. alata), Polygonum hydropiper L. (P. hydropiper) or Diplazium esculentum (Retz.) Sw. (D. esculentum), respectively. The relative standard deviations of the repeatability was Doxycycline contents obtained by this new method and by the reference methods reported in literature were in agreement at 95% confidence level with the paired t-test. The sample throughput was 36 h- 1 for each green reagent.

  4. Flow Injection/Sequential Injection Analysis Systems: Potential Use as Tools for Rapid Liver Diseases Biomarker Study

    Directory of Open Access Journals (Sweden)

    Supaporn Kradtap Hartwell

    2012-01-01

    Full Text Available Flow injection/sequential injection analysis (FIA/SIA systems are suitable for carrying out automatic wet chemical/biochemical reactions with reduced volume and time consumption. Various parts of the system such as pump, valve, and reactor may be built or adapted from available materials. Therefore the systems can be at lower cost as compared to other instrumentation-based analysis systems. Their applications for determination of biomarkers for liver diseases have been demonstrated in various formats of operation but only a few and limited types of biomarkers have been used as model analytes. This paper summarizes these applications for different types of reactions as a guide for using flow-based systems in more biomarker and/or multibiomarker studies.

  5. SEMI-CONTINUOUS DETERMINATION OF NO2 IN PASSIVE DIFFUSERS BY FLOW INJECTION/UV-VIS SPECTROPHOTOMETRY

    Directory of Open Access Journals (Sweden)

    Iliana M. de la Garza-Rodríguez

    2015-06-01

    Full Text Available In this work the development of a semi-automated method by flow injection for spectrophotometric indirect determination of NO2, is described. The gas of environmental importance is captured through passive diffusers built in the laboratory, where it undergoes a reaction with triethanolamine to form nitrite ions in relation 1:1, which are determined after the derivatization with sulfanilamide and N-(1-naphthyl ethylenediamine. It’s concluded that the proposal method is quick and easy, as well as sensitive and selective to determine the chemical specie of interest. The estimated NO2 concentration in the air of Saltillo in Coahuila was 2.6 ± 0.3 mg m-3, which was above the maximum recommended by NOM-023-SSA1-1993 norm.

  6. Simultaneous topographic and amperometric membrane mapping using an AFM probe integrated biosensor.

    Science.gov (United States)

    Stanca, Sarmiza Elena; Csaki, Andrea; Urban, Matthias; Nietzsche, Sandor; Biskup, Christoph; Fritzsche, Wolfgang

    2011-02-15

    The investigation of the plasma membrane with intercorrelated multiparameter techniques is a prerequisite for understanding its function. Presented here, is a simultaneous electrochemical and topographic study of the cell membrane using a miniaturized amperometric enzymatic biosensor. The fabrication of this biosensor is also reported. The biosensor combines a scanning force microscopy (AFM) gold-coated cantilever and an enzymatic transducer layer of peroxidases (PODs). When these enzymes are brought in contact with the substrate, the specific redox reaction produces an electric current. The intensity of this current is detected simultaneously with the surface imaging. For sensor characterization, hydroquinone-2-carboxylic acid (HQ) is selected as an intrinsic source of H(2)O(2). HQ has been electrochemically regenerated by the reduction of antraquinone-2-carboxylic acid (AQ). The biosensor reaches the steady state value of the current intensity in 1 ± 0.2s.

  7. An amperometric enzyme biosensor for real-time measurements of cellobiohydrolase activity on insoluble cellulose

    DEFF Research Database (Denmark)

    Cruys-Bagger, Nicolaj; Guilin, Ren; Tatsumi, Hirosuke;

    2012-01-01

    An amperometric enzyme biosensor for continuous detection of cellobiose has been implemented as an enzyme assay for cellulases. We show that the initial kinetics for cellobiohydrolase I, Cel7A from Trichoderma reesei, acting on different types of cellulose substrates, semi-crystalline and amorphous......) and this provided experimental access to the transient kinetics of cellobiohydrolases acting on insoluble cellulose. The response from the CDH-biosensor during enzymatic hydrolysis was corrected for the specificity of PcCDH for the β-anomer of cello-oligosaccharides and the approach were validated against HPLC....... It is suggested that quantitative, real-time data on pure insoluble cellulose substrates will be useful in attempts to probe the molecular mechanism underlying enzymatic hydrolysis of cellulose...

  8. Dual enzymatic biosensor for simultaneous amperometric determination of histamine and putrescine.

    Science.gov (United States)

    Henao-Escobar, W; del Torno-de Román, L; Domínguez-Renedo, O; Alonso-Lomillo, M A; Arcos-Martínez, M J

    2016-01-01

    A disposable electrodic system consisting of two working electrodes connected in array mode has been developed for the simultaneous determination of histamine (His) and putrescine (Put). Histamine deshydrogenase and putrescine oxidase enzymes were respectively immobilized by crosslinking on each working screen-printed electrode, both modified with tetrathiafulvalene. The dual system allowed the simultaneous amperometric determination of both species by measuring the oxidation current of the mediator in each working electrode. The effect of other potentially interfering biogenic amines was also evaluated. The capability of detection was of 8.1 ± 0.7 for His and 10 ± 0.6 μM for Put. The precision in terms of relative standard deviation was of 3.5% and 6.7% for His and Put, respectively. The developed biosensor was successfully applied to the determination of His and Put in different food samples.

  9. Amperometric Determination of Indole-3-acetic Acid Based on Platinum Nanowires and Carbon Nanotubes

    Institute of Scientific and Technical Information of China (English)

    Ruo Zhong WANG; Lang Tao XIAO; Ming Hui YANG; Jun Hui DING; Feng Li QU; Guo Li SHEN

    2006-01-01

    Platinum nanowire (PtNW) can be grown by electrodeposition in polycarbonate membrane, with the average diameter of the nanowires about 250 nm. The PtNW and multiwalled carbon nanotubes (CNT) are then dispersed into chitosan (CHIT) solution. The resulting PtNW-CNT-CHIT material brings new capabilities for electrochemical devices by using the synergistic action of the electrocatalytic activity of PtNW and CNT. By dropping the PtNW-CNT-CHIT film onto the glassy carbon (GC) electrode surface, and after evaporationan amperometric sensor for the determination of indole-3-acetic acid (IAA) was developed. The oxidation current of IAA increased significantly at the PtNW-CNT-CHIT film coated GC electrode,in contrast to that at the CNT-CHIT modified GC. The linear response of the sensor is from 50ng/ml to 50 μg/ml with a detection limit of 25 ng/mL.

  10. A CMOS analog front-end chip for amperometric electrochemical sensors

    Science.gov (United States)

    Zhichao, Li; Yuntao, Liu; Min, Chen; Jingbo, Xiao; Jie, Chen

    2015-07-01

    This paper reports a complimentary metal-oxide-semiconductor (CMOS) analog front-end chip for amperometric electrochemical sensors. The chip includes a digital configuration circuit, which can communicate with an external microcontroller by employing an I2C interface bus, and thus is highly programmable. Digital correlative double samples technique and an incremental sigma-delta analog to digital converter (Σ-Δ ADC) are employed to achieve a new proposed system architecture with double samples. The chip has been fabricated in a standard 0.18-μm CMOS process with high-precision and high-linearity performance occupying an area of 1.3 × 1.9 mm2. Sample solutions with various phosphate concentrations have been detected with a step concentration of 0.01 mg/L. Project supported by the National Key Basic Research and Development Project (No. 2015CB352103).

  11. Automated determination of bromide in waters by ion chromatography with an amperometric detector

    Science.gov (United States)

    Pyen, G.S.; Erdmann, D.E.

    1983-01-01

    An automated ion chromatograph, including a program controller, an automatic sampler, an integrator, and an amperometric detector, was used to develop a procedure for the determination of bromide in rain water and many ground waters. Approximately 10 min is required to obtain a chromatogram. The detection limit for bromide is 0.01 mg l-1 and the relative standard deivation is <5% for bromide concentrations between 0.05 and 0.5 mg l-1. Chloride interferes if the chloride-to-bromide ratio is greater than 1 000:1 for a range of 0.01-0.1 mg l-1 bromide; similarly, chloride interferes in the 0.1-1.0 mg l-1 range if the ratio is greater than 5 000:1. In the latter case, a maximum of 2 000 mg l-1 of chloride can be tolerated. Recoveries of known concentrations of bromide added to several samples, ranged from 97 to 110%. ?? 1983.

  12. A green synthetic strategy of nickel hexacyanoferrate nanoparticals supported on the graphene substrate and its non-enzymatic amperometric sensing application

    Science.gov (United States)

    xue, Zhonghua; He, Nan; Rao, Honghong; Hu, Chenxian; Wang, Xiaofen; Wang, Hui; Liu, Xiuhui; Lu, Xiaoquan

    2017-02-01

    Rapid glucose detection is a key requirement for both diagnosis and treatment of diabetes. A facile and green strategy to achieve spherical-shaped nickel hexacyanoferrate (NiHCF) nanoparticals supported on electrochemical reduction graphene oxide by using electrochemical cyclic voltammetry is explored. As a sensing substrate, electrochemical reduction graphene oxide deposited on a glassy carbon electrode surface exhibited obvious positive effect on the electrodeposition of NiHCF nanoparticals with spherical structure and thus effectively improved the electrical conductivity and electrochemical sensing of the proposed amperometric sensor. Proof-concept experiments demonstrated that the proposed nanocomposites modified electrode exhibited excellent sensitivity toward glucose oxidation as well as with a satisfying detection limit of 0.11 μM. More importantly, we also explore that as a simple, green and facile method, electrochemical technology can be employed and provide a new strategy for developing GO and metal hexacyanoferrate based amperometric sensing platform toward glucose and other biomolecules.

  13. Determination of formaldehyde in Brazilian alcohol fuels by flow-injection solid phase spectrophotometry

    OpenAIRE

    Teixeira, Leonardo Sena Gomes; Leão, Elsimar S.; Dantas,Alailson Falcão; Pinheiro, Heloísa Lúcia C.; Costa, Antonio Celso Spinola; Andrade,Jailson Bittencourt de

    2004-01-01

    p. 711–715 In thiswork, a solid phase spectrophotometric method in association with flowinjection analysis for formaldehyde determination has been developed with direct measurement of light-absorption in C18 material. The 3,5-diacetyl-1,4-dihydrolutidine produced from the reaction between formaldehyde and fluoral P was quantitatively retained on C18 support and the spectrophotometric detection was performed simultaneously at 412 nm. The retained complex was quickly eluted from C18 mater...

  14. Real-Time Telemetry System for Amperometric and Potentiometric Electrochemical Sensors

    Directory of Open Access Journals (Sweden)

    Ching-Hsing Luo

    2011-09-01

    Full Text Available A real-time telemetry system, which consists of readout circuits, an analog-to-digital converter (ADC, a microcontroller unit (MCU, a graphical user interface (GUI, and a radio frequency (RF transceiver, is proposed for amperometric and potentiometric electrochemical sensors. By integrating the proposed system with the electrochemical sensors, analyte detection can be conveniently performed. The data is displayed in real-time on a GUI and optionally uploaded to a database via the Internet, allowing it to be accessed remotely. An MCU was implemented using a field programmable gate array (FPGA to filter noise, transmit data, and provide control over peripheral devices to reduce power consumption, which in sleep mode is 70 mW lower than in operating mode. The readout circuits, which were implemented in the TSMC 0.18-μm CMOS process, include a potentiostat and an instrumentation amplifier (IA. The measurement results show that the proposed potentiostat has a detectable current range of 1 nA to 100 μA, and linearity with an R2 value of 0.99998 in each measured current range. The proposed IA has a common-mode rejection ratio (CMRR greater than 90 dB. The proposed system was integrated with a potentiometric pH sensor and an amperometric nitrite sensor for in vitro experiments. The proposed system has high linearity (an R2 value greater than 0.99 was obtained in each experiment, a small size of 5.6 cm × 8.7 cm, high portability, and high integration.

  15. Slurry sampling flow injection chemical vapor generation inductively coupled plasma mass spectrometry for the determination of trace Ge, As, Cd, Sb, Hg and Bi in cosmetic lotions

    Energy Technology Data Exchange (ETDEWEB)

    Chen, Wei-Ni [Department of Chemistry, National Sun Yat-sen University, Kaohsiung 80424, Taiwan (China); Jiang, Shiuh-Jen, E-mail: sjjiang@faculty.nsysu.edu.tw [Department of Chemistry, National Sun Yat-sen University, Kaohsiung 80424, Taiwan (China); Department of Medical Laboratory Science and Biotechnology, Kaohsiung Medical University, Kaohsiung 80708, Taiwan (China); Chen, Yen-Ling [Department of Fragrance and Cosmetic Science, Kaohsiung Medical University, Kaohsiung 80708, Taiwan (China); Sahayam, A.C. [National Centre for Compositional Characterisation of Materials (CCCM), Hyderabad (India)

    2015-02-20

    Highlights: • Determination of Ge, As, Cd, Sb, Hg and Bi in cosmetic lotions in a single run. • Accurate analysis using isotope dilution and standard addition methods. • Vapor generation ICP-MS yielded superior detection limits compared to ETV-ICP-MS. • No sample dissolution increased sample through put. • Analysis of GBW09305 Cosmetic (Cream) reference material for accuracy. - Abstract: A slurry sampling inductively coupled plasma mass spectrometry (ICP-MS) method has been developed for the determination of Ge, As, Cd, Sb, Hg and Bi in cosmetic lotions using flow injection (FI) vapor generation (VG) as the sample introduction system. A slurry containing 2% m/v lotion, 2% m/v thiourea, 0.05% m/v L-cysteine, 0.5 μg mL{sup −1} Co(II), 0.1% m/v Triton X-100 and 1.2% v/v HCl was injected into a VG-ICP-MS system for the determination of Ge, As, Cd, Sb, Hg and Bi without dissolution and mineralization. Because the sensitivities of the analytes in the slurry and that of aqueous solution were quite different, an isotope dilution method and a standard addition method were used for the determination. This method has been validated by the determination of Ge, As, Cd, Sb, Hg and Bi in GBW09305 Cosmetic (Cream) reference material. The method was also applied for the determination of Ge, As, Cd, Sb, Hg and Bi in three cosmetic lotion samples obtained locally. The analysis results of the reference material agreed with the certified value and/or ETV-ICP-MS results. The detection limit estimated from the standard addition curve was 0.025, 0.1, 0.2, 0.1, 0.15, and 0.03 ng g{sup −1} for Ge, As, Cd, Sb, Hg and Bi, respectively, in original cosmetic lotion sample.

  16. On-line complexation/cloud point preconcentration for the sensitive determination of dysprosium in urine by flow injection inductively coupled plasma-optical emission spectrometry

    Energy Technology Data Exchange (ETDEWEB)

    Ortega, Claudia; Cerutti, Soledad; Silva, Maria F. [Departamento de Quimica Analitica, Facultad de Quimica, Bioquimica y Farmacia, Universidad Nacional de San Luis, Chacabuco y Pedernera, 5700, San Luis (Argentina); Olsina, Roberto A.; Martinez, Luis D. [Departamento de Quimica Analitica, Facultad de Quimica, Bioquimica y Farmacia, Universidad Nacional de San Luis, Chacabuco y Pedernera, 5700, San Luis (Argentina); Consejo Nacional de Investigaciones Cientificas y Tecnicas (CONICET), Avda. Rivadavia 1917, CP C1033AAJJ, Buenos Aires (Argentina)

    2003-01-01

    An on-line dysprosium preconcentration and determination system based on the hyphenation of cloud point extraction (CPE) to flow injection analysis (FIA) associated with ICP-OES was studied. For the preconcentration of dysprosium, a Dy(III)-2-(5-bromo-2-pyridylazo)-5-diethylaminophenol complex was formed on-line at pH 9.22 in the presence of nonionic micelles of PONPE-7.5. The micellar system containing the complex was thermostated at 30 C in order to promote phase separation, and the surfactant-rich phase was retained in a microcolumn packed with cotton at pH 9.2. The surfactant-rich phase was eluted with 4 mol L{sup -1} nitric acid at a flow rate of 1.5 mL min{sup -1}, directly in the nebulizer of the plasma. An enhancement factor of 50 was obtained for the preconcentration of 50 mL of sample solution. The detection limit value for the preconcentration of 50 mL of aqueous solution of Dy was 0.03 {mu}g L{sup -1}. The precision for 10 replicate determinations at the 2.0 {mu}g L{sup -1}Dy level was 2.2% relative standard deviation (RSD), calculated from the peak heights obtained. The calibration graph using the preconcentration system for dysprosium was linear with a correlation coefficient of 0.9994 at levels near the detection limits up to at least 100 {mu}g L {sup -1}. The method was successfully applied to the determination of dysprosium in urine. (orig.)

  17. Sensitive determination of mercury in tap water by cloud point extraction pre-concentration and flow injection-cold vapor-inductively coupled plasma optical emission spectrometry

    Science.gov (United States)

    de Wuilloud, Jorgelina C. A.; Wuilloud, Rodolfo G.; Silva, María. F.; Olsina, Roberto A.; Martinez, Luis D.

    2002-02-01

    A pre-concentration and determination methodology for mercury at trace levels in water samples was developed. Cloud point extraction was successfully employed for the pre-concentration of mercury prior to inductively coupled plasma optical emission spectrometry coupled to a flow injection with cold vapor generation system. The mercury was extracted as mercury-2-(5-bromo-2-pyridylazo)-5-diethylaminophenol [Hg(II)-(5-Br-PADAP)] complex, at pH 9.2 mediated by micelles of the non-ionic surfactant polyethyleneglycolmono- p-nonylphenylether (PONPE 5). Cold vapor generation was developed from 100 μl of the extracted surfactant-rich phase by means of a stannous chloride (SnCl 2) solution as reluctant. An exhaustive study of the variables affecting the cloud point extraction with PONPE 5 and cold vapor mercury generation from the surfactant phase was performed. The 50-ml sample solution pre-concentration allowed us to raise an enrichment factor of 200-fold. The lower limit of detection obtained under the optimal conditions was 4 ng l -1. The precision for 10 replicate determinations at the 0.5-μg l -1 Hg level was 3.4% relative standard deviation (R.S.D.), calculated with the peak heights. The calibration graph using the pre-concentration system for mercury was linear with a correlation coefficient of 0.9998 at levels near the detection limits up to at least 50 μg l -1. The method was successfully applied to the determination of mercury in tap water samples.

  18. Determination of thiomersal by flow injection coupled with microwave-assisted photochemical online oxidative decomposition of organic mercury and cold vapor atomic fluorescence spectroscopy

    Energy Technology Data Exchange (ETDEWEB)

    Campanella, Beatrice; Onor, Massimo; Mascherpa, Marco Carlo; D’Ulivo, Alessandro [National Research Council of Italy, C.N.R., Istituto di Chimica dei Composti Organo Metallici-ICCOM-UOS Pisa, Area di Ricerca, Via G. Moruzzi 1, 56124 Pisa (Italy); Ferrari, Carlo [National Research Council of Italy, C.N.R., Istituto Nazionale di Ottica, INO–UOS Pisa, Area di Ricerca, Via G. Moruzzi 1, 56124 Pisa (Italy); Bramanti, Emilia, E-mail: bramanti@pi.iccom.cnr.it [National Research Council of Italy, C.N.R., Istituto di Chimica dei Composti Organo Metallici-ICCOM-UOS Pisa, Area di Ricerca, Via G. Moruzzi 1, 56124 Pisa (Italy)

    2013-12-04

    Graphical abstract: -- Highlights: •Thiomersal was determined on line using FI-MW/UV-CVGAFS. •MW/UV allows a “green” on line oxidation of organic mercury to Hg{sup II}. •Each measure requires less than 5 min with a LOD of 3 ng mL{sup −1} (as mercury). •Hg concentration in commercial ophthalmic solutions ranges between 7.5 and 59.0 μg mL{sup −1}. -- Abstract: We developed a flow injection (FI) method for the determination of thiomersal (sodium ethylmercurithiosalicylate, C{sub 9}H{sub 9}HgNaO{sub 2}S) based on the UV/microwave (MW) photochemical, online oxidation of organic mercury, followed by cold vapor generation atomic fluorescence spectrometry (CVG-AFS) detection. Thiomersal was quantitatively converted in the MW/UV process to Hg(II), with a yield of 97 ± 3%. This reaction was followed by the reduction of Hg(II) to Hg(0) performed in a knotted reaction coil with NaBH{sub 4} solution, and AFS detection in an Ar/H{sub 2} miniaturized flame. The method was linear in the 0.01–2 μg mL{sup −1} range, with a LOD of 0.003 μg mL{sup −1}. This method has been applied to the determination of thiomersal in ophthalmic solutions, with recoveries ranging between 97% and 101%. We found a mercury concentration in commercial ophthalmic solutions ranging between 7.5 and 59.0 μg mL{sup −1}.

  19. Preconcentration and determination of trace elements with 2,6-diacetylpyridine functionalized Amberlite XAD-4 by flow injection and atomic spectroscopy.

    Science.gov (United States)

    Kara, Derya; Fisher, Andrew; Hill, Steve J

    2005-11-01

    An on-line flow injection method for the direct determination of trace elements in environmental samples is described. A mini-column packed with 2,6-diacetylpyridine functionalized Amberlite XAD-4 was used to preconcentrate and separate 8 trace metals (Cd, Co, Cu, Mn, Ni, Pb, U and Zn) from water and extracts from solid samples. The metals were eluted with 0.1 M HNO(3) directly to the detection system (either inductively coupled plasma-mass spectrometry (ICP-MS) or flame atomic absorption spectrometry (FAAS)). As well as demonstrating that the resin could be used to preconcentrate ultra-trace analytes from natural waters, it was also shown to work well at a pH of 5.5. Therefore, after treatment of sample digests with sodium fluoride, samples that contain extremely large concentrations of iron may be analysed for trace analytes without the excess iron overloading the capacity of the resin. To this end, the analytes Cd, Co, Cu and Ni were preconcentrated from acid extracts of certified soil/sediment samples and then eluted with nitric acid to be determined on-line. Limits of detection (3sigma) of Cd = 0.33 microg l(-1), Co = 0.094 microg l(-1), Cu = 0.34 microg l(-1), Mn = 0.32 microg l(-1), Ni = 0.30 microg l(-1), Pb = 0.43 microg l(-1), U = 0.067 microg l(-1) and Zn = 0.20 microg l(-1) for the FI-ICP-MS system and Cd = 22 microg l(-1), Co = 60 microg l(-1), Cu = 10 microg l(-1) and Ni = 4.8 microg l(-1) for the FI-FAAS system were obtained. Analysis of certified reference materials showed good agreement with the certified values using the two methods.

  20. Simultaneous determination of Folpet and Metalaxyl in pesticide formulations by flow injection Fourier transform infrared spectrometry

    Energy Technology Data Exchange (ETDEWEB)

    Quintas, Guillermo; Armenta, Sergio; Morales-Noe, Asuncion; Garrigues, Salvador; Guardia, Miguel de la

    2003-03-17

    Fourier transform infrared (FTIR) spectrometric methodology has been developed for the simultaneous determination of Folpet and Metalaxyl in pesticide formulations. The method involves the extraction of both active principles by sonication of the sample with CHCl{sub 3} and direct measurement of the absorbance using peak height values at 1798 cm{sup -1} corrected with a baseline defined at 1810 cm{sup -1} for Folpet, and peak area data established from 1677 to 1667 cm{sup -1} corrected using a baseline from 1692 to 1628 cm{sup -1} for Metalaxyl. Limits of detection (3 s) values of 17 and 16 {mu}g g{sup -1} were found for Folpet and Metalaxyl, respectively, with results comparable with those found by liquid chromatography with UV detection. The new method involves a considerable decrease in solvent consumption. The automation of the procedure by incorporating on-line dissolution and filtration of the samples allows complete mechanisation of the method and improves the safety of operation.