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Sample records for carbazides

  1. Preconcentration of Copper Using 1,5-Diphenyl Carbazide as the Complexing Agent via Dispersive Liquid-Liquid Microextraction and Determination by Flame Atomic Absorption Spectrometry

    OpenAIRE

    Reyhaneh Rahnama; Elaheh Shafiei; Mohammad Reza Jamali

    2013-01-01

    We report a simple and sensitive microextraction system for the preconcentration and determination of Cu (II) by flame atomic absorption spectrometry (FAAS). Dispersive liquid-liquid microextraction is a modified solvent extraction method and its acceptor-to-donor phase ratio is greatly reduced compared with other methods. In the proposed approach, 1,5-diphenyl carbazide (DPC) was used as a copper ion selective complexing agent. Several variables such as the extraction and dispersive solvent ...

  2. Preconcentration of Copper Using 1,5-Diphenyl Carbazide as the Complexing Agent via Dispersive Liquid-Liquid Microextraction and Determination by Flame Atomic Absorption Spectrometry

    Directory of Open Access Journals (Sweden)

    Reyhaneh Rahnama

    2013-01-01

    Full Text Available We report a simple and sensitive microextraction system for the preconcentration and determination of Cu (II by flame atomic absorption spectrometry (FAAS. Dispersive liquid-liquid microextraction is a modified solvent extraction method and its acceptor-to-donor phase ratio is greatly reduced compared with other methods. In the proposed approach, 1,5-diphenyl carbazide (DPC was used as a copper ion selective complexing agent. Several variables such as the extraction and dispersive solvent type and volume, pH of sample solution, DPC concentration, extraction time, and ionic strength were studied and optimized for a quantitative preconcentration and determination of copper (II and at the optimized conditions: 60 μL, 0.5 mL, and 5 mL of extraction solvent (chloroform, disperser solvent (ethanol, and sample volume, respectively, a linear calibration graph was obtained over the concentration range of 10–200 μg L−1 for Cu (II with R2 = 0.9966. The limit of detection (3Sb/m, and preconcentration factor are 2 μg L−1 and 25, respectively. The relative standard deviation (n=10 at 100 μg L−1 of Cu (II is 2.5%. The applicability of the developed technique was evaluated by application to spiked environmental water samples.

  3. Inhibitory effect of some carbazides on corrosion of aluminium in hydrochloric acid and sodium hydroxide solutions

    Energy Technology Data Exchange (ETDEWEB)

    Fouda, A.S. [El-Mansoura Univ. (Egypt). Dept. of Chemistry; Madkour, L.H. [Tanta Univ. (Egypt). Dept. of Chemistry; Elshafei, A.A. [El-Mansoura Univ. (Egypt). Dept. of Chemistry; Elasklany, A.H. [El-Mansoura Univ. (Egypt). Dept. of Chemistry

    1995-06-01

    The dissolution of aluminium in hydrochloric acid and sodium hydroxide solutions in the presence of semicarbazide, thiosemicarbazide and sym.diphenylcarbazide as corrosion inhibitors has been studied using thermometric, weight-loss and polarization methods. The three methods gave consistent results. The higher inhibition efficiency of these compounds in acidic than in alkaline madia may be due to the less negative potential of aluminium in hydrochloric acid solution, favouring adsorption of the additive. The adsorption of these compounds were found to obey Frumkin adsorption isotherm. Cathodic polarization measurements showed that these compounds are cathodic inhibitors and their adsorption in the double layer does not change the mechanism of the hydrogen evolution reaction. The results are analysed in terms of both molecular and cationic adsorption. (orig.)

  4. [Selenazoles. XII. (1) Reaction of 4-(p-tolyl)-selenosemi-carbazides of acetic, benzoic, isonicotinic, nicotinic and picolinic acid with omega-acetophenone].

    Science.gov (United States)

    Biliński, S; Bielak, L; Chmielewski, J; Marcewicz-Rojewska, B; Musik, I

    1989-01-01

    The cyclization of 4-(p-tolyl)-selenosemicarbazides of acetic, benzoic, isonicotinic, nicotinic and picolinic acids (Ia-e) with omega-bromoacetophenone was investigated in the medium of methanol (Method A) or in methanol in the presence of anhydrous sodium acetate (Method B). Acid hydrolysis of compounds IIf-i and IVa-c, e was studied. Results of UV and IR spectrometric measurements and of the in vitro microbiological studies are presented. In contradistinction to corresponding thiosemicarbazides, the change in N4 nitrogen atom basicity of the parent selenosemicarbazide I (pKa of p-toluidine = 5.1), in comparison to that of 4-phenyl-selenosemicarbazide (pKa of aniline = 4.63), proved to influence the equilibrium of the reaction with omega-bromoacetophenone only in the methanol medium without addition of anhydrous sodium acetate (Method A).

  5. 二苯卡巴肼分光光度法对有机-无机复混肥料中铬含量测定的研究%Study of Determination of Chromium Content in Organo-Mineral Compound Fertilizers by Diphenyl Carbazide Spectrophotometry

    Institute of Scientific and Technical Information of China (English)

    杨晓霞

    2000-01-01

    铬是有机-无机复混肥料中的有害元素之一,我国尚未制定有机-无机复混肥料中铬含量测定的标准。本文探索了采用二苯卡巴肼分光光度法测定铬含量的条件,并通过精密度、回收率和不同方法的比较试验,表明该方法时有机-无机复混肥料中铬含量的测定是可行的,也是可靠的,为以后制定相应的国家标准打下了基础。

  6. Poly(ethylene glycol)-supported Liquid-phase Parallel Synthesis of Di(aryloxyacetyl)thiosemicarbazides

    Institute of Scientific and Technical Information of China (English)

    Xi Cun WANG; Jun Ke WANG; Zheng LI

    2004-01-01

    An efficient poly(ethylene glycol) (PEG)-supported liquid-phase parallel approach to di(aryloxyacetyl)thiosemicarbazides is described. PEG-bound phenol reacted with chloroacetic acid to afford PEG-bound phenyloxyacetic acid, which was readily converted into corresponding phenyloxyacetyl chloride. Subsequent nucleophilic substitution with ammonium thiocyanate followed by addition of aryloxyacetic acid hydrazides gave PEG-bound di(aryloxyacetyl)thiosemi- carbazides, which were easily cleaved to give the resulting library of 1-aryloxyacetyl-4-(4'- methoxylcarbonylphenyloxyacetyl)thiosemicarbazides in good to high yield and high purity.

  7. Novel “turn on” fluorescent sensors based on anthracene and carbazone units for Cu (II) ion in CH{sub 3}CN–H{sub 2}O

    Energy Technology Data Exchange (ETDEWEB)

    Erdemir, Serkan, E-mail: serdemir82@gmail.com; Malkondu, Sait

    2015-02-15

    Two novel anthracene-based receptors containing Schiff base and urea groups (AOC and ATC) were synthesized in one step and full characterized. The optical properties of receptors AOC and ATC towards metal ions were investigated by UV–visible and fluorescence spectroscopy. It was found that both receptors AOC and ATC show highly selectivity towards Cu{sup 2+} over other 17 metal ions in CH{sub 3}CN–H{sub 2}O (9/1, v/v). - Highlights: • Novel fluorescent sensors based on anthracene and carbazide AOC and ATC were synthesized. • The optical properties of AOC and ATC were observed by UV–visible and fluorescence spectroscopy. • AOC and ATC showed highly selective and sensitive to Cu{sup 2+} over other 17 metal ions.

  8. Nano-sized silica supported FeCl3 as an efficient heterogeneous catalyst for the synthesis of 1,2,4-triazine derivatives

    Institute of Scientific and Technical Information of China (English)

    Davood Habibi; Somayyeh Vakili

    2015-01-01

    The one‐pot synthesis of a series of 1,2,4‐triazines from the reactions of semicarbazide or thiosemi‐carbazide with various α,β‐dicarbonyl compounds under reflux conditions in a EtOH‐H2O (9:1) mixture as solvent and catalyzed by nano‐sized silica supported FeCl3 (FeCl3@SiO2) was investigat‐ed. The FeCl3 content of the catalyst was measured by atomic absorption to get the adsorption ca‐pacity. The reactions gave high yields of the product and the catalyst was easily separated and re‐used for successive reaction runs without significant loss of activity.

  9. Groundwater contaminant by hexavalent chromium

    Energy Technology Data Exchange (ETDEWEB)

    Parsons, C. [Univ. of Texas, Austin, TX (United States)

    1995-11-01

    Oxidation of trivalent chromium to hexavalent chromium has been investigated as a function of total manganese in soils as well as various incubation conditions. Chromium and manganese contents were analyzed by atomic absorption (graphite furnace and flame emission respectively) following acid digestion. Total hexavalent chromium generation capacity was determined by addition of 0.001 M CrCL3, incubation, and analysis by s-diphenyl carbazide. Samples were then leached with CaSO{sub 4} and MgSO{sub 4} and incubated in various environments (oven, freeze-drier, field moist, ultrafreeze) to test for geogenic generation of Cr(IV). The degree of geogenic generation of hexavalent chromium was compared with total Mn and Cr content as well as hexavalent generational capacity.

  10. Novel Steroidal (6R)-Spiro-1,3,4-thiadiazoline Derivatives as Anti-bacterial Agents

    Institute of Scientific and Technical Information of China (English)

    Khan Salman A.; Asiri, Abdullah M.

    2012-01-01

    Novel steroidal (6R)-spiro-1,3,4-thiadiazoline derivatives have been synthesized by the cyclization of steroidal thiosemiearbazones. Thiosemicarbazones have been synthesized by the reaction of steroidal ketones with thiosemi- carbazide. All the compounds have been characterized by IR, 1H NMR, mass and elemental analyses. The antibacterial activities of these compounds have been first tested in vitro by the disk diffusion assay against two Gram-positive and two Gram-negative bacteria, and then the minimum inhibitory concentration (MIC) values have been determined with the reference of standard drug amoxicillin. The results showed that steroidal thiadiazoline de- rivatives exhibited better antibacterial activity than the steroidal thiosemicarbazone derivatives. Chloro and acetoxy substituents on the 3β-position of the steroidal thiadiazoline ring increased the anti-bacterial activity. Among all the compounds, compounds 7 and 8 were found better inhibitors as compared to the respective drug amoxicillin.

  11. Synthesis and application of ion-imprinted polymer nanoparticles for the determination of nickel ions

    Science.gov (United States)

    Abbasi, Shahryar; Roushani, Mahmoud; Khani, Hossein; Sahraei, Reza; Mansouri, Ghobad

    2015-04-01

    Novel Ni(II) ion-imprinted polymers (Ni-IIP) nanoparticles were prepared by using Ni(II) ion-1,5-diphenyl carbazide (DPC) complex as the template molecule and methacrylic acid, ethylene glycol dimethacrylate (EGDMA) and 2,2‧-azobisisobutyronitrile (AIBN) as the functional monomer, cross-linker and the radical initiator, respectively. The synthesized polymer particles were characterized physically and morphologically by using infrared spectroscopy (IR), thermo gravimetric analysis (TGA), X-ray diffraction (XRD) and scanning electron microscopic (SEM) techniques. Some parameters such as pH, weight of the polymer, adsorption time, elution time, eluent type and eluent volume which affects the efficiency of the polymer were studied. The preconcentration factor, relative standard deviation, and limit of detection of the method were found to be 100, 1.9%, and 0.002 μg mL-1, respectively. The prepared ion-imprinted polymer particles have an increased selectivity toward Ni(II) ions over a range of competing metal ions with the same charge and similar ionic radius. The method was applied to the determination of nickel in tomato and some water samples.

  12. Confirmation of hydroxyl radicals (•OH) generated in the presence of TiO2 supported on AC under microwave irradiation.

    Science.gov (United States)

    Zhang, Zhaohong; Yu, Fengyang; Huang, Lirong; Jiatieli, Jianaerguli; Li, Yuanyuan; Song, Lijun; Yu, Ning; Dionysiou, Dionysios D

    2014-08-15

    In order to study the degradation mechanism of technology of microwave (MW) combined with TiO2 supported on activated carbon (TiO2/AC), the reactive oxygen species (ROS) was explored through oxidation of 1,5-diphenyl carbazide (DPCI) to 1,5-diphenyl carbazone (DPCO). Furthermore, 2,6-di-tert-butyl-4-methylphenol (BHT), Mannitol (MT) and Vitamin C (VC) were used as radical scavengers to confirm the generation of the hydroxyl radicals ((•)OH). In addition, the influence of some parameters such as TiO2 mass ratio content, irradiation time, material dose, DPCI concentration and MW power on the determination of (•)OH were examined. The results showed that the (•)OH could be generated under MW combined with loaded TiO2/AC. Also, anatase TiO2/AC can generate more (•)OH radicals than rutile TiO2/AC under MW irradiation. This work would provide new mechanistic insights on the enhanced degradation effect of organic pollutants in water using the supported TiO2/AC coupled with MW technology.

  13. Copper Toxicity Affects Photosystem II Electron Transport at the Secondary Quinone Acceptor, QB1

    Science.gov (United States)

    Mohanty, Narendranath; Vass, Imre; Demeter, Sándor

    1989-01-01

    The nature of Cu2+ inhibition of photosystem II (PSII) photochemistry in pea (Pisum sativum L.) thylakoids was investigated monitoring Hill activity and light emission properties of photosystem II. In Cu2+-inhibited thylakoids, diphenyl carbazide addition does not relieve the loss of Hill activity. The maximum yield of fluorescence induction restored by hydroxylamine in Tris-inactivated thylakoids is markedly reduced by Cu2+. This suggests that Cu2+ does not act on the donor side of PSII but on the reaction center of PSII or on components beyond. Thermoluminescence and delayed luminescence studies show that charge recombination between the positively charged intermediate in water oxidation cycle (S2) and negatively charged primary quinone acceptor of pSII (QA−) is largely unaffected by Cu2+. The S2QB− charge recombination, however, is drastically inhibited which parallels the loss of Hill activity. This indicates that Cu2+ inhibits photosystem II photochemistry primarily affecting the function of the secondary quinone electron acceptor, QB. We suggest that Cu2+ does not block electron flow between the primary and secondary quinone acceptor but modifies the QB site in such a way that it becomes unsuitable for further photosystem II photochemistry. PMID:16666731

  14. Oxidation-extraction spectrometry of reactive oxygen species (ROS) generated by chlorophyllin magnesium (Chl-Mg) under ultrasonic irradiation.

    Science.gov (United States)

    Guo, Yuwei; Cheng, Chunping; Wang, Jun; Jin, Xudong; Liu, Bin; Wang, Zhiqiu; Gao, Jingqun; Kang, Pingli

    2011-09-01

    In order to examine the mechanism and process of sonodynamic reaction, the chlorophyllin magnesium (Chl-Mg) acting as a sonosensitizer was irradiated by ultrasound, and the generation of reactive oxygen species (ROS) were detected by the method of oxidation-extraction spectrometry (OES). That is, under ultrasonic irradiation in the presence of Chl-Mg, the 1,5-diphenyl carbazide (DPCI) is oxidized by generated ROS into 1,5-diphenyl carbazone (DPCO), which can be extracted by mixed organic solvent and display a obvious visible absorption at 563 nm wavelength. Besides, the generation conditions of ROS were also reviewed. The results demonstrated that the quantities of generated ROS increased with the increase of ultrasonic irradiation time, Chl-Mg concentration and DPCI concentration. Finally, several radical scavengers (l-Histidine (His), 2,6-Di-tert-butyl-methylphenol (BHT) and Vitamin C (VC)) were used to determine the kind of the generated ROS. It was found that at least the hydroxyl radical (OH) and singlet oxygen (1O2) were generated in the presence of Chl-Mg under ultrasonic irradiation. It is wish that this paper might offer some valuable references for the study on the mechanism of SDT and the application of Chl-Mg in tumor treatment.

  15. Detection and comparison of reactive oxygen species (ROS) generated by chlorophyllin metal (Fe, Mg and Cu) complexes under ultrasonic and visible-light irradiation.

    Science.gov (United States)

    Wang, Jun; Guo, Yuwei; Gao, Jingqun; Jin, Xudong; Wang, Zhiqiu; Wang, Baoxin; Li, Kai; Li, Ying

    2011-09-01

    In this paper, in order to examine the mechanisms of sonodynamic and photodynamic reactions, the chlorophyllin metal (Chl-M (M=Fe, Mg and Cu)) complexes were irradiated by ultrasound (US) and visible-light (VL), respectively, and the generation of reactive oxygen species (ROS) were detected by the method of Oxidation-Extraction Spectrometry (OES). That is, the 1,5-diphenyl carbazide (DPCI) is oxidized by the generated ROS into 1,5-diphenyl carbazone (DPCO), which can display a various visible absorption around 563 nm wavelength. Besides, some influence parameters on the generation of ROS were also reviewed. The results demonstrated an apparent synergistic effect of Chl-M and ultrasonic or visible-light irradiation for the generation of ROS. Moreover, the quantities of generated ROS increase with the increase of (ultrasonic or visible-light) irradiation time and Chl-M (M=Fe, Mg and Cu) concentration. Finally, several quenchers were used to determine the kind of the generated ROS. It is wished that this paper might offer some valuable references for the study on the sonodynamic therapy (SDT) and photodynamic therapy (PDT) mechanisms and the application of Chl-M in tumor treatment.

  16. A novel solidified floating organic drop microextraction method for preconcentration and determination of copper ions by flow injection flame atomic absorption spectrometry.

    Science.gov (United States)

    Sahin, Ciğdem Arpa; Tokgöz, Ilknur

    2010-05-14

    A rapid, simple and cost effective solidified floating organic drop microextraction (SFODME) and flow injection flame atomic absorption spectrometric determination (FI-FAAS) method for copper was developed. In this method, a free microdrop of 1-undecanol containing 1,5-diphenyl carbazide (DPC) as the complexing agent was transferred to the surface of an aqueous sample including Cu(II) ions, while being agitated by a stirring bar in the bulk of the solution. Under the proper stirring conditions, the suspended microdrop can remain at the top-center position of the aqueous sample. After the completion of the extraction, the sample vial was cooled by placing it in a refrigerator for 10min. The solidified microdrop was then transferred into a conical vial, where it melted immediately and diluted to 300microL with ethanol. Finally, copper ions in 200microL of diluted solution were determined by FI-FAAS. Several factors affecting the microextraction efficiency, such as type of extraction solvent, pH, complexing agent concentration, extraction time, stirring rate, sample volume and temperature were investigated and optimized. Under optimized conditions for 100mL of solution, the preconcentration factor was 333 and the enrichment factor was 324. The limit of detection (3s) was 0.4ngmL(-1), the limit of quantification (10s) was 1.1ngmL(-1) and the relative standard deviation (RSD) for 10 replicate measurements of 10ngmL(-1) copper was 0.9%. The proposed method was successfully applied to the determination of copper in different water samples.

  17. Biotic stress induced demolition of thylakoid structure and loss in photoelectron transport of chloroplasts in papaya leaves.

    Science.gov (United States)

    Nanda, Rashmi Madhumita; Biswal, Basanti

    2008-04-01

    Papaya mosaic virus (PMV) causes severe mosaic symptoms in the papaya (Carica papaya L.) leaves. The PMV-induced alterations in photosystem II (PS II) structure and photochemical functions were probed. An increase in chlorophyll a (Chl a) fluorescence polarization suggests pathogen-induced transformation of thylakoid membrane to a gel phase. This transformation in physical state of thylakoid membrane may result in alteration in topology of pigments on pigment-binding proteins as reflected in pathogen-induced loss in the efficiency of energy transfer from carotenoids to chlorophylls. The fast Chl a fluorescence induction kinetics of healthy and PMV-infected plants by F(O)-F(J)-F(I)-F(P) transients revealed pathogen-induced perturbation on PS II acceptor side electron transfer equilibrium between Q(A) and Q(B) and in the pool size of electron transport acceptors. Pathogen-induced loss in photosynthetic pigments, changes in thylakoid structure and decrease in the ratio of F(V)/F(M) (photochemical potential of PS II) further correlate with the loss in photoelectron transport of PS II as probed by 2,6-dichlorophenol indophenol (DCPIP)-Hill reaction. Restoration of the loss by 1,5-diphenyl carbazide (DPC), an exogenous electron donor, that donates electron directly to reaction centre II bypassing the oxygen evolving system (OES), leads towards the conclusion that OES is one of the major targets of biotic stress. Further, the data suggest that chlorophyll fluorescence could be used as a non-invasive handy tool to assess the loss in photosynthetic efficiency and symptom severity in infected green tissues vis-a-vis the healthy ones.

  18. Confirmation of hydroxyl radicals ({sup •} OH) generated in the presence of TiO{sub 2} supported on AC under microwave irradiation

    Energy Technology Data Exchange (ETDEWEB)

    Zhang, Zhaohong, E-mail: lnuhjhx@163.com [School of Environmental Science, Liaoning University, Shenyang 110036 (China); Yu, Fengyang; Huang, Lirong; Jiatieli, Jianaerguli; Li, Yuanyuan; Song, Lijun [School of Environmental Science, Liaoning University, Shenyang 110036 (China); Yu, Ning [Experiment Center of Environmental Monitoring of Liaoning Province, Shenyang 110161 (China); Dionysiou, Dionysios D., E-mail: dionysios.d.dionysiou@uc.edu [Environmental Engineering and Science Program, University of Cincinnati, Cincinnati, OH 45221-0012 (United States)

    2014-08-15

    Graphical abstract: - Highlights: • Generation of {sup •} OH in MW integrated with loaded TiO{sub 2}/AC system was confirmed. • Confirmation of {sup •} OH was conducted using radical scavenger such as BHT, MT and VC. • More {sup •} OH was formed using anatase TiO{sub 2}/AC than rutile TiO{sub 2}/AC under MW irradiation. • Effect of mass ratio, irradiation time, catalyst dose and DPCI on {sup •} OH was studied. - Abstract: In order to study the degradation mechanism of technology of microwave (MW) combined with TiO{sub 2} supported on activated carbon (TiO{sub 2}/AC), the reactive oxygen species (ROS) was explored through oxidation of 1,5-diphenyl carbazide (DPCI) to 1,5-diphenyl carbazone (DPCO). Furthermore, 2,6-di-tert-butyl-4-methylphenol (BHT), Mannitol (MT) and Vitamin C (VC) were used as radical scavengers to confirm the generation of the hydroxyl radicals ({sup •} OH). In addition, the influence of some parameters such as TiO{sub 2} mass ratio content, irradiation time, material dose, DPCI concentration and MW power on the determination of {sup •} OH were examined. The results showed that the {sup •} OH could be generated under MW combined with loaded TiO{sub 2}/AC. Also, anatase TiO{sub 2}/AC can generate more {sup •} OH radicals than rutile TiO{sub 2}/AC under MW irradiation. This work would provide new mechanistic insights on the enhanced degradation effect of organic pollutants in water using the supported TiO{sub 2}/AC coupled with MW technology.

  19. Photoinhibition of photosynthesis in needles of two cypress (Cupressus sempervirens) clones.

    Science.gov (United States)

    La Porta, Nicola; Bertamini, Massimo; Nedunchezhian, Namachevayam; Raddi, Paolo; Muthuchelian, Krishnasamy

    2005-08-01

    Photoinhibition of photosynthesis and photosynthetic recovery were studied in detached needles of cypress (Cupressus sempervirens L.) Clones 52 and 30 under controlled conditions of high irradiation (about 1900 micromol m(-2) s(-1) for 60 min; HL treatment), followed by 60 min in darkness. The degree of photoinhibition was determined based on the ratio of variable to maximum chlorophyll fluorescence (Fv/Fm), which is a measure of the potential efficiency of photosystem II (PSII), and on electron transport measurements. The Fv/Fm ratio declined in needles of both clones in response to the HL treatment. Minimal fluorescence (Fo) increased in HL-treated needles of both clones. The HL treatment decreased rates of whole-chain and PSII activity of isolated thylakoids more in Clone 52 than in Clone 30. In needles of both clones, PSI activity was less sensitive to photoinhibition than PSII activity. In the subsequent 60-min dark incubation, fast recovery was observed in needles of both clones, with PSII efficiencies reaching similar values to those in non-photoinhibited needles. The artificial exogenous electron donors diphenyl carbazide (DPC), hydroxylamine (NH2OH) and manganese chloride (MnCl2) failed to restore the HL-induced loss of PSII activity in needles of Clone 30, whereas DPC and NH2OH significantly restored PSII activity in photoinhibited needles of Clone 52. Quantification of the PSII reaction center protein D1 and the 33-kDa protein of the water-splitting complex following HL treatment of needles revealed pronounced differences between Clone 52 and Clone 30. The large decrease in PSII activity in HL-treated needles was caused by the marked loss of D1 protein and 33-kDa protein in Clone 30 and Clone 52, respectively.

  20. Low temperature reduction of hexavalent chromium by a microbial enrichment consortium and a novel strain of Arthrobacter aurescens

    Directory of Open Access Journals (Sweden)

    Thompson Vicki S

    2006-01-01

    Full Text Available Abstract Background Chromium is a transition metal most commonly found in the environment in its trivalent [Cr(III] and hexavalent [Cr(VI] forms. The EPA maximum total chromium contaminant level for drinking water is 0.1 mg/l (0.1 ppm. Many water sources, especially underground sources, are at low temperatures (less than or equal to 15 Centigrade year round. It is important to evaluate the possibility of microbial remediation of Cr(VI contamination using microorganisms adapted to these low temperatures (psychrophiles. Results Core samples obtained from a Cr(VI contaminated aquifer at the Hanford facility in Washington were enriched in Vogel Bonner medium at 10 Centigrade with 0, 25, 50, 100, 200, 400 and 1000 mg/l Cr(VI. The extent of Cr(VI reduction was evaluated using the diphenyl carbazide assay. Resistance to Cr(VI up to and including 1000 mg/l Cr(VI was observed in the consortium experiments. Reduction was slow or not observed at and above 100 mg/l Cr(VI using the enrichment consortium. Average time to complete reduction of Cr(VI in the 30 and 60 mg/l Cr(VI cultures of the consortium was 8 and 17 days, respectively at 10 Centigrade. Lyophilized consortium cells did not demonstrate adsorption of Cr(VI over a 24 hour period. Successful isolation of a Cr(VI reducing organism (designated P4 from the consortium was confirmed by 16S rDNA amplification and sequencing. Average time to complete reduction of Cr(VI at 10 Centigrade in the 25 and 50 mg/l Cr(VI cultures of the isolate P4 was 3 and 5 days, respectively. The 16S rDNA sequence from isolate P4 identified this organism as a strain of Arthrobacter aurescens, a species that has not previously been shown to be capable of low temperature Cr(VI reduction. Conclusion A. aurescens, indigenous to the subsurface, has the potential to be a predominant metal reducer in enhanced, in situ subsurface bioremediation efforts involving Cr(VI and possibly other heavy metals and radionuclides.

  1. Chromium(III, VI) speciation analysis with preconcentration on a maleic acid-functionalized XAD sorbent

    Energy Technology Data Exchange (ETDEWEB)

    Yalcin, Sibel; Apak, Resat

    2004-03-03

    Chromium may exist in environmental waters as Cr(III) and Cr(IV), the latter being the toxic and carcinogenic form. Since atomic absorption spectrometry (AAS) and inductively coupled plasma atomic emission spectrometry can only yield information on total Cr concentration, a polymer resin bearing O,O-donor chelating groups such as the maleic acid-functionalized XAD-(CO)CH-CH-COOH resin was synthesized to selectively retain Cr(III) at pH 4.0-5.5. The dynamic breakthrough capacity of the resin for Cr(III) at pH 5.0 was 7.52 mg g{sup -1}, and the preconcentration factor extended to 250-300. Chromium(III) in the presence of 250-fold Cr(VI)--which was not retained--could be effectively preconcentrated on the NH{sub 4}{sup +}-form of the resin and determined by AAS or diphenylcarbazide (DPC) spectrophotometry. When Cr(VI) was reduced to Cr(III) with Na{sub 2}SO{sub 3} solution brought to pH 1 by the addition of 1 M H{sub 2}SO{sub 4}, and preconcentrated on the resin, total Cr could be determined. The developed method was validated with a blended coal sample CRM-1632. Since the adsorption behavior as a function of pH of possible interferent metal ions, e.g. Ni(II), Co(II), Cu(II), Cd(II), Zn(II), Pb(II) and Fe(III), was similar to that of Cr(III), selective elution of Cr(III) from the resin was realized using a mixture of 1 wt.% H{sub 2}O{sub 2}+1 M NH{sub 3}. The eluate containing Cr as chromate could be directly analyzed by diphenyl carbazide spectrophotometry without any adverse effect from the common interferents of this method, i.e. Fe(III), Cu(II) Hg(II), VO{sub 3}{sup -}, MoO{sub 4}{sup 2-} and WO{sub 4}{sup 2-}. Various synthetic waste solutions typical of electroplating bath effluents containing Cr, Cu, Ni, Zn, Na, Ca, cyanide (and chemical oxidation demand (COD), achieved by glucose addition) were subjected to pretreatment procedures such as hypochlorite oxidation (of cyanide) and catalytic oxidation (of COD) with peroxodisulfate. Chromium determination gave

  2. Studies of nanosecond pulsed power for modifications of biomaterials and nanomaterials (SWCNT)

    Science.gov (United States)

    Chen, Meng-Tse

    This work investigates the modification of biological materials through the applications of modern nanosecond pulsed power, along with other forms of nanotechnologies. The work was initially envisaged as a study of the effect of intense nanosecond pulsed electric fields on cancer cells. As the work progressed, the studies suggested incorporation of additional technologies, in particular, cold plasmas, and carbon nanotubes. The reasons for these are discussed below, however, they were largely suggested by the systems that we were studying, and resulted in new and potentially important medical therapies. Using nanosecond cold plasmas powered with nanosecond pulses, collaboration with endodontists and biofilm experts demonstrated a killing effect on biofilms deep within root canals, suggesting a fundamentally new approach to an ongoing problem of root canal sterilization. This work derived from the application of nanosecond pulsed power, resulting in effective biofilm disinfection, without excessive heating, and is being investigated for additional dental and other medical applications. In the second area, collaboration with medical and nanotube experts, studies of gliomamultiforme (GBM) led to the incorporation of functionalized carbon nanotubes. Single-walled carbon nanotube-fluorescein carbazide (SWCNT-FC) conjugates demonstrated that the entry mechanism of the single-walled carbon nanotubes (SWCNTs) was through an energy-dependent endocytotic pathway. Finally, a monotonic pH sensitivity of the intracellular fluorescence emission of SWCNT-FC conjugates in human ovarian cancer cells suggests these conjugates may serve as intracellular pH sensors. Light-stimulated intracellular hydrolysis of the amide linkage and localized intracellular pH changes are proposed as mechanisms. The use of SWCNTs for cancer therapy of gliomas, resulting in hyperthermia effect after 808 nm infrared radiations, absorbed specifically by SWCNTs but not by biological tissue. Heat was only

  3. Leaf plasticity to light intensity in Italian cypress (Cupressus sempervirens L.): adaptability of a Mediterranean conifer cultivated in the Alps.

    Science.gov (United States)

    Baldi, Paolo; Muthuchelian, Krishnasamy; La Porta, Nicola

    2012-12-05

    Italian cypress (Cupressus sempervirens L.) is native to the eastern Mediterranean, an area characterised by hot, dry summers and mild winters. Over the centuries, however, the species has been introduced into more northerly regions, a long way from its native range. The current, generally warmer climatic conditions brought about by global warming have favoured its cultivation in even more northerly areas in the Alps and other European alpine regions. Given that not only temperature, but also light availability are limiting factors for the spread of cypress in these environments, it is important to ascertain how this species copes with low light conditions. The photosynthetic characteristics of cypress leaves collected from different portions of the crown with contrasting light availability were evaluated by several methods. Chlorophyll a (Chl a), chlorophyll b (Chl b) and carotenoid (Car) content was found to be higher in shade leaves than in sun leaves when measured on a fresh mass basis, although enzymatic activities of ribulose-1,5-bisphosphate carboxylase/oxygenase (RuBisCo) and nitrate reductase were lower in shade leaves. When the efficiency of PSII was measured by chlorophyll fluorescence, a marked reduction in F(m) was found in shade leaves, while F(o) remained unchanged. The use of exogenous electron donors diphenyl carbazide (DPC) and NH(2)OH actually improved the photosynthetic efficiency of shade leaves, and the same effect was found when PSII electron transport activity was measured as O(2) evolution. Altogether, these results seem to indicate lesser photosynthetic efficiency in shade leaves, probably an impairment on the donor side of the PSII. At the same time, analysis by SDS-PAGE revealed differences in the polypeptide composition of the thylakoid membranes of sun and shade leaves: the bands corresponding to 23 kDa, 28-25 kDa and 33 kDa polypeptides were less intense in the thylakoid membranes extracted from shade leaves. These results were