Sample records for derivatization
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Sample records 1 - 20 shown. Select sample records:



1

Análise de glicocorticosteróides por CG-EM: uma nova abordagem de derivatização para o controle de dopagem no esporte/ Analisys of glucocorticosteroids by GC-MS: a new approach of derivatization step for doping control in sport

Pereira, Henrique M. G.; Marques, Marlice A. S.; Cardoso, Jarí N.; Aquino Neto, Francisco R.
2002-12-01

Resumo em inglês Glucocorticosteroids (CT) show a powerful anti-inflammatory effect. In view of this, they are extensively used in sports medicine, but their misuse (systemic administration) can lead to severe injuries on athletes and has been restricted by the IOC in recent years. For GC-MS analysis, a derivatization step is necessary in order to convert them to a stable form, thus preventing thermal breakdown with the loss of the ketone side chain. Derivatization of CT is reviewed and a new approach of silylation is presented for screening of CT in urine.

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2

Determinação de 2,5-hexanodiona em urina empregando cromatografia líquida de alta eficiência, após derivatização com 2,4-dinitrofenil-hidrazina/ Determination of 2,5-hexanedione in urine by high performance liquid chromatography after derivatization with 2,4-dinitrophenilhidrazine

Antunes, Marina Venzon; Feltraco, Lilian de Lima; Morisso, Fernando Dal Pont; Linden, Rafael
2011-01-01

Resumo em inglês A method for quantifying urinary 2,5-hexanedione was optimized and validated. Urine samples were hydrolyzed and derivatized with 2,4-dinitrophenylhydrazine. The analyte was separated in a high performance liquid chromatography system with a diode array detector, using a C18 column (150 x 4.6 mm, p.d. 5 µm) and a mobile phase composed of phosphate buffer pH 2.3:acetonitrile (40:60, v/v), at a flow rate of 1 mL/min. The chromatograms were monitored at 334 nm. Retention tim (mais) e was 7.3 minutes. Main validation parameters were: coefficient of determination: 0.9994, accuracy: 96 to 107%; intra-assay precision (RSD): 3.08 to 6.72%; inter-assay precision (RSD): 2.54 to 8.17% and limit of quantitation of 0.19 µg/mL.

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3

Estudo pré-analítico e de validação para determinação de malondialdeído em plasma humano por cromatografia líquida de alta eficiência, após derivatização com 2,4-dinitrofenilhidrazina/ Preanalytical and validation studies for the determination of malondialdehyde in human plasma through high performance liquid chromatography after derivatization with 2,4-dinitrophenylhydrazine

Antunes, Marina Venzon; Lazzaretti, Camilla; Gamaro, Giovana Duzzo; Linden, Rafael
2008-06-01

Resumo em português O malondialdeído (MDA) é um importante biomarcador utilizado na avaliação do estresse oxidativo. O objetivo deste estudo foi desenvolver uma metodologia para a quantificação plasmática de MDA, através de cromatografia líquida de alta eficiência com detecção por arranjo de diodos (CLAE-DAD), após processo de derivatização com 2,4-dinitrofenilhidrazina (DNPH), avaliando as principais variáveis pré-analíticas. A curva de calibração em plasma (0 a 40 µM) (mais) apresentou elevada linearidade (r²=0,998). Os principais parâmetros de validação foram: recuperação absoluta: 78%; limite de detecção: 0,11 µM e limite de quantificação: 0,38 µM. Os valores de MDA determinados em indivíduos adultos saudáveis (n=38) foram 3,31 ± 0,38 µM (média ± DP). Estudos de estabilidade do padrão de MDA, reagente derivatizante e MDA plasmáticos, indicaram que a solução padrão pode ser armazenada a -20 e 4 ºC. Resumo em inglês Malondialdehyde (MDA) is an important biomarker for the evaluation of oxidative stress status. The aim of this study was to develop a method for plasma MDA quantification by high performance liquid chromatography with diode-array detection (HPLC-DAD), following derivatization with 2,4-dinitrophenylhydrazine (DNPH), evaluating the main preanalytical variables. The calibration curve in plasma (0 to 40 µM) presented high linearity (r² = 0.998). Main validation parameters w (mais) ere: recovery: 78%; LOD: 0.11 µM and LOQ: 0.38 µM. The MDA values obtained in healthy volunteers (n=38) were 3.31 ± 0.38 µM (mean ± SD). Stability studies of MDA standard solution and derivatizing reagent and plasma MDA indicated that the standard solution can be stored at -20 and 4 ºC, remaining stable for at least 30 days.

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4

Determinação de ácido valpróico em soro por cromatografia líquida de alta eficiência com detector de arranjo de diodos (CLAE-DAD), após derivatização com brometo de fenacila/ Determination of valproic acid in serum by high performance liquid chromatography with diode array detection (HPLC-DAD), after derivatization with phenacyl bromide

Antunes, Marina Venzon; Nagel, Viviane; Linden, Rafael; Werlang, Helenice Orosco; Hermes, Daniela
2009-01-01

Resumo em inglês Valproic acid (VA) is a drug used to control seizures in several epileptic conditions. In VA pharmacotherapy, therapeutic drug monitoring is recommended to obtain adequate seizure control and avoid toxicity. The aim of this study was to validate a method for the determination of valproic acid in serum, employing high performance liquid chromatography with diode array detection (HPLC-DAD), after derivatization with phenacyl bromide. The calibration curve (y=0.0133x-0.0025) (mais) presented good linearity with r²=0.9999. Accuracy (101-115%), intra-assay precision (4.53-8.15%) and inter-assay precision (3.15-6.77%) were acceptable. The quantification limit was 2.0 µg/mL. The method presented similar results to enzyme immunoassay.

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5

Determinação de resíduos de avermectinas em fígado bovino por cromatografia líquida de alta eficiência/ Determination of avermectins residues in bovine liver by high performance liquid chromatography

Souza, Scheilla V. C.; Silva, Gilsara; Diniz, Maria Helena G. M.; Santos, Eleonora V.; Lima, Josefa A.; Teodoro, João C.
2003-04-01

Resumo em português Foi padronizado e validado um método analítico para determinação de resíduos de abamectin, doramectin e ivermectin em fígado bovino empregando extração com acetonitrila, purificação com cartucho de C18 , derivatização, detecção e quantificação por CLAE/FL. Nos ensaios com amostras adicionadas de solução padrão em níveis entre 5 e 100mg/kg as recuperações médias obtidas variaram de 69,0 a 101,4% com valores de coeficiente de variação entre 5,5 e 28,1%. O limite de detecção e quantificação do método, para os três resíduos estudados, foi 5µg/kg. Resumo em inglês A method for determination of abamectin, doramectin and ivermectin residues in bovine liver was standardized and validated using acetonitrile extraction, clean-up with nd C18 cartridges, derivatization, detection and quantification by HPLC/FL. In the assays using spiked samples in levels varying from 5 to 100mg/kg the average recovery values ranged from 69.0 to 101.4% with coefficient of variation values between 5.5 and 28.1%. The limit of detection and quantification of this method, for each studied residue, was 5µg/kg.

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6

Carboximetilação de polpas de bagaço de cana-de-açúcar e caracterização dos materiais absorventes obtidos/ Carboxymethylation of pulps from sugar cane bagasse and characterization of the produced absorbent materials

Morais, Luís C.; Campana Filho, Sérgio P.
1999-12-01

Resumo em português Os processos soda/antraquinona e etanol/água foram aplicados à produção de polpas de fibras e de medulas de bagaço de cana-de-açúcar. Tais polpas foram carboximetiladas em suspensão de isopropanol/água (8/1 m/m) por 4 horas a 80(0)C, empregando a relação molar 8,5/5,4/1 para ácido monocloroacético/hidróxido de sódio/celulose. Os graus médios de susbtituição dos produtos carboximetilados foram determinados por espectroscopia ¹H R.M.N. e variaram entre 0, (mais) 44 e 1,27 em função da polpa empregada na derivatização. Os derivados mais substituídos foram os melhores absorventes, sugerindo que a capacidade de retenção de água desses produtos está diretamente associada a seus graus de substituição. Resumo em inglês Two pulping methods were used on fibers and pith of sugar cane bagasse: soda/anthraquinone and ethanol/water. These pulps were submitted to carboxymethylation in a slurry of isopropanol/water (8/1 m/m) at 80ºC for 4 hours using a molar relation 8,8/5,4/1 of monochloroacetic acid/sodium hydroxyde/cellulose. The average degrees of substitution of the carboxymethylated products, determined by ¹H N.M.R. spectroscopy, were between 0.44 and 1.27, depending on the pulp employe (mais) d for derivatization. The more substituted pulps were the more absorbent products, suggesting that the water retention capacity of these products is closely associated to their degrees of substitution.

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7

Preparo de hidrolisados protéicos para a análise de aminoácidos/ Preparation of protein hydrolysates for amino acid analysis

Bernardi, Carlos Roberto; Luiz, Marilde Terezinha Bordignon; Zanotto, Dirceu Luiz; Guidoni, Antônio Lourenço
2003-12-01

Resumo em português Amostras de milho, farelo de soja e hidrolisado ácido de caseína foram submetidas à hidrólise ácida em estufa (110 ± 5°C, durante 22horas) com ácido clorídrico 6 N, em ampolas de vidro seladas sob vácuo. Os hidrolisados foram preparados por quatro métodos: 1) evaporação em evaporador rotativo sob vácuo; 2) evaporação em câmaras a vácuo em presença de pastilhas de NaOH; 3) evaporação em bloco de aquecimento sob fluxo de argônio; 4) neutraliza (mais) ção com solução padrão de citrato/NaOH. Os aminoácidos foram separados e quantificados em analisador específico Beckman System 6300 com derivatização pós-coluna por ninidrina. O método de neutralização dos reagentes da hidrólise apresentou os melhores resultados considerando todos os aminoácidos. Além disso, foi mais rápido e prático no preparo de um grande número de amostras. Quanto aos métodos de evaporação, o uso de evaporador rotativo apresentou perdas significativas apenas para treonina e serina na amostra farelo de soja; sob fluxo de argônio observou-se baixos teores para treonina, fenilalanina e lisina; em câmara sob vácuo verificou-se perdas significativas para treonina, serina e tirosina. Resumo em inglês Samples of corn, soybean corn and casein (acid hydrolysate) were submitted to acid hydrolysis in oven (110 ± 5°C, for 22 hours) with 6 N HCl in sealed ampoules under vacuum. Four methods of hydrolysate preparation were used: 1) evaporation to dryness in rotary evaporator under vacuum, 2) evacuated desiccator under vacuum and NaOH, 3) flushing the open vial with argon and 4) neutralisation with standard citrate/NaOH solution. Amino acids were isolated and quanti (mais) fied in specific analyzer Beckman System 6300 with ninhidrin post-column derivatization. The neutralization method presented the best result considering all analysed amino acids. Besides, it was more practical for rapid processing of a large number of samples. With regard to the evaporation methods in the rotary evaporator, significant losses were verified only for threonine and serine in the soybean sample. Under flow of argon, low recoveries of threonine, phenylalanine and lysine where observed, whereas in the evacuated desiccator, significant losses of threonine, serine and tyrosine where verified.

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8

Utilização de RMN de ¹H na determinação da configuração absoluta de álcoois/ Utilization of ¹H NMR in the determination of absolute configuration of alcohols

Barreiros, Marizeth L.; David, Jorge M.; David, Juceni P.
2005-12-01

Resumo em inglês This review reports the determination of absolute configuration of primary and secondary alcohols by ¹H NMR spectroscopy, using the Mosher method. This method consists in the derivatization of an alcohol possessig unknown absolute configuration with one or both enantiomers of an auxiliary reagent. The resulting diastereoisomer spectra are registered and compared, and the chemical shift differences (DdR,S = deltaR - deltaS) are measured. The deter (mais) mination of the absolute configuration of the alcohol molecule is based on the correlation between its chiral center and the auxiliary reagent's chiral center. Therefore, the determination of the absolute configuration depends on aromatic ring shielding effects on the substituents of the alcohol as evidenced by the ¹H NMR spectrum.

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9

Terpenos e ácidos graxos de Dipteryx lacunifera Ducke/ Terpenes and fatty acids from Dipteryx lacunifera Ducke

Vieira Júnior, Gerardo Magela; Silva, Hilris Rocha e; Bittencourt, Thaís Chaves; Chaves, Mariana H.; Simone, Carlos Alberto de
2007-01-01

Resumo em inglês This paper describes the isolation of the furanocassane-type diterpene, named vinhaticoic acid, along with beta-farnesene and spatulenol from fruit shells of D. lacunifera. Structural determinations were accomplished by chemical derivatization and spectral analysis, including 1D and 2D NMR and X-ray crystallography. The fatty portion was extracted from the fruit kernels, transesterfied and analysed by HRGC/MS. Oleic acid (75.8 ± 4.3%) was the major component. Essen (mais) tial oil extracted from the fruit shells of D. lacunifera was analysed by HRGC/MS and nine sesquiterpenes were identified; beta-farnesene (48.6%) and spatulenol (21.61%) were the major constituents.

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10

Sulfonamidas em leite por cromatografia líquida de alta eficiência com derivação pré-coluna e detecção por fluorescência/ Sulfonamides in milk by high performance liquid chromatography with pre-column derivatization and fluorescence detection

Alaburda, Janete; Ruvieri, Valter; Shundo, Luzia; Almeida, Adriana Palma de; Tiglea, Paulo; Sabino, Myrna
2007-11-01

Resumo em português O objetivo deste trabalho foi avaliar e validar um método para deteminação de resíduos de sulfatiazol (STZ), sulfametazina (SMZ) e sulfadimetoxina (SDM) em leite UHT integral. A extração foi realizada com diclorometano e coluna de extração em fase sólida de sílica. Os resíduos, após derivação com fluorescamina, foram quantificados por cromatografia líquida de alta eficiência com detector de fluorescência. O limite de detecção das três sulfas em amostra (mais) de leite integral foi 0,3 µg L-1 e o limite de quantificação foi 1 µg L-1 para STZ e SMZ e 2,5 µg L-1 para SDM, com coeficientes de variação entre 4,4 e 6,6%. Os valores de recuperação para STZ, SMZ e SDM foram 63,2, 91,2 e 63,2%, respectivamente. Considerando o limite máximo de resíduo estabelecido pela legislação brasileira de 100 µg kg-1 para a soma das concentrações totais de STZ, SMZ e SDM, o método descrito permite a determinação simultânea dos três analitos em amostras de leite UTH integral. Resumo em inglês The objective of this work was to evaluate and validate a method for analysis of sulfathiazole (STZ), sulfamethazine (SMZ) and sulfadimethoxine (SDM) residues in milk. Extraction was carried out with diclhoromethane followed by silica solid phase extraction. The extracts were derivatizated with fluorescamine and quantified by reversed-phase high performance liquid chromatography with fluorescence detection. The detection limit for the three sulfonamides was 0.3 µg L-1 an (mais) d the quantification limit was 1 µg L-1 for STZ and SMZ and 2.5 µg L-1 for SDM, with coefficient of variation ranging from 4.4 to 6.6%. The recoveries for STZ, SMZ and SDM were 63.2, 91.2 and 63.2%, respectively. Considering that Brazilian regulation sets maximum residue limit in milk of 100 µg kg-1 for total sulfonamide concentrations (STZ, SMZ and SDM), the present method is adequate to quantify the residues of three sulfonamides simultaneously in UHT milk.

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11

Substituição parcial do farelo de soja por soja integral extrusada na dieta de leitões desmamados/ Partial substitution of soybean meal by full-fat extruded soybean in diets for weaned piglets

Bertol, Teresinha Marisa; Mores, Nelson; Franke, Márcia Regina
2001-06-01

Resumo em português Foi desenvolvido um estudo com dois experimentos para avaliação da soja integral extrusada (SIE) como substituta parcial do farelo de soja (FS) na dieta pré-inicial para leitões desmamados aos 21 dias de idade. Em cada experimento foram comparados quatro níveis (0, 20, 40 e 60%) de substituição do FS pela SIE. A substituição do FS pela SIE no experimento 1 provocou aumento linear do consumo diário de ração (CRD) e da conversão alimentar (CA), sem efeito sobre (mais) o ganho de peso diário (GPD) no período total da creche. A altura média da mucosa (AMM) do jejuno inferior reduziu linearmente e a do duodeno apresentou efeito quadrático com o aumento dos níveis de SIE na dieta. No experimento 2, a substituição do FS pela SIE proporcionou efeito quadrático sobre o GPD, o CRD e o peso médio ao final da fase de creche (PM35). Foi concluído que a substituição parcial do farelo de soja pela soja integral extrusada na dieta de leitões desmamados aos 21 dias de idade melhorou o desempenho dos leitões na fase inicial após o desmame. No experimento 1, não foi possível determinar qual o valor máximo de substituição do farelo de soja pela soja integral extrusada, uma vez que houve resposta linear no GPD até o nível de 60% de substituição. No entanto, no experimento 2, o melhor resultado de ganho de peso, estimado por intermédio da derivação da equação quadrática, foi de 26,82% de substituição do farelo de soja pela soja integral extrusada, para o período de 0 a 14 dias após o desmame. Resumo em inglês A study including two experiments was carried out to evaluate partial substitution of soybean meal (SM) by full-fat extruded soybean (ES) in the pre-starter diet, for piglets weaned at 21 days of age. In each experiment four levels (0, 20, 40 and 60%) of substitution of SM by ES were compared. In the first experiment, daily feed intake (DFI) and feed:gain ratio linearly increased for the total nursery period, due to substitution of SM by ES. Daily gain (DG) was not affect (mais) ed. Average height of the intestinal mucousa (HIM) in the low jejunum was linearly reduced, and in the duodenum had a quadratic effect, when ES was increased. In the experiment 2, DG, DFI and body weight at the end of the nursery phase (BW35) had a quadratic response, in consequence of substitution of SM by ES. It was concluded that partial substitution of SM by ES in the pre-starter diet for piglets weaned at 21 days of age provide an improvement for performance of piglets in the initial period after weaning. In the experiment 1, it was not possible to determine the maximum value for substitution of SM by ES, because DG showed a linear response until 60% of substitution. However, in the experiment 2, the best result for DG, estimated through the derivatization of the quadratic equation, was obtained at 26.82% of substitution, from 0 to 14 days post weaning.

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12

Resina de Protium heptaphyllum: isolamento, caracterização estrutural e avaliação das propriedades térmicas/ The Protium heptaphyllum resin: isolation, structural characterization and evaluation of thermal properties

Vieira Júnior, Gerardo Magela; Souza, Cleide Maria Leite de; Chaves, Mariana Helena
2005-03-01

Resumo em inglês Three mixtures of triterpenes (maniladiol and breine; alpha and beta-amyrin; lupenone, alpha and beta-amyrinone) were isolated from Protium heptaphyllum March resin. The structural identification was based on NMR and mass spectrometry data. Lupenone, and alpha and beta-amyrinone were not reported before as constituents of this resin. The resin was submitted to methylation and acetylation reactions. The pure and derivatized resins and the mixtures (maniladiol and breine; a (mais) lpha and beta-amyrin) were analyzed by TG and DSC. The TG curves revealed that the derivatization decreases the thermal stability of the resin. The DSC curves showed peaks that can be assigned to evaporation and phase transitions processes.

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13

Otimização de metodologia para derivação de desoxinivalenol através de planejamento experimental/ Optimization of the methodology for deoxynivalenol derivatization by experimental planning

Garda, Jaqueline; Badiale-Furlong, Eliana
2008-01-01

Resumo em inglês The objective of this work was to optimize the derivatization reaction for determining deoxynivalenol (DON) by gas chromatography employing an experimental planning procedure. The factors were: temperature, reaction time, catalyst and trifluoroacetic anhydride concentration. The relative peak areas were used to evaluated the effects. The best conditions for DON derivatization were 200 µL TFAA and 18 mg sodium bicarbonate for 6 min at 74 ºC for 7 to 21 µg of DON. Under these conditions, the detection limit was 1.4 µg of DON.

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14

O uso de radiação ultravioleta para o pré-tratamento de amostras em análise inorgânica/ Use of UV radiation for sample pretreatment in inorganic analysis

Cavicchioli, Andrea; Gutz, Ivano Gebhardt Rolf
2003-12-01

Resumo em inglês The basic principles of UV irradiation as sample pre-treatment step and its potential for inorganic analysis are illustrated and discussed through significant examples from the literature. Not only does this overview cover the classical applications of this technique in the decomposition of organic matter in electroanalysis, but it also presents recent trends, including the increasing interest in employing UV irradiation in flow analytical systems, successful attempts to (mais) enhance its effectiveness and the coupling with chromatographic and spectroscopic methodologies. Furthermore, a number of relevant cases of UV-driven derivatization reactions involving photo-sensitive inorganic species are presented, showing some convenient options to perform fast and reliable determination of inorganic and organic analytes.

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15

Metodologias analíticas para determinação das fumonisinas em milho e alimentos à base de milho/ Analitycal metodologies for the determination of fumonisins in maize and maize-based food products

Lino, Celeste M.; Silva, Liliana J. G.; Pena, Angelina S.
2006-04-01

Resumo em inglês Fumonisins are mycotoxins occurring worldwide, mainly in maize and maize-based food products, which could affect animal and human health. This paper reviews analytical methodologies for the determination of these fungal toxins in foods. It includes extraction, cleanup, derivatization procedures, detection, quantification, and confirmation procedures. Initial attempts at gas chromatographic methods and thin layer chromatography were supplanted by liquid chromatographic met (mais) hods, mainly performed with fluorometric detection, or mass spectrometry detection, enabling the analysis of polar and thermolabile chemicals without chemical derivatization, which results in lower limits of detection. Alternative methods, such as enzyme linked immunosorbent assay or zone capillary zone electrophoresis, are also described.

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16

Marcadores orgânicos de contaminação por esgotos sanitários em sedimentos superficiais da baía de Santos, São Paulo/ Organic markers of sewage contamination in surface sediments from Santos bay, São Paulo

Martins, César de Castro; Gomes, Fernanda Boechat Azeredo; Ferreira, Juliana Aureliano; Montone, Rosalinda Carmela
2008-01-01

Resumo em inglês Organic markers, such as sterols and ketones, were used to assess sewage contamination in sediments from the Santos Bay, SP, and its continental shelf. These compounds were analyzed by GC/FID after soxhlet extraction, clean up and derivatization. The concentration of coprostanol and ratios between selected sterols were used to evaluate fecal contamination. The stations located in the mid-western part of the Santos Bay presented organic matter from sewage due to the input (mais) of fecal material from the city of Santos by submarine sewage outfall. Stations located at the continental shelf did not present fecal contamination. Coprostanol levels in sewage outfall stations were higher in comparison to other Brazilian coastal areas, except Guanabara Bay/RJ, and could be related to the fraction of the population without sewage treatment.

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17

Extração sortiva em barra de agitação para análise de fármacos em fluidos biológicos/ Stir-bar sorptive extraction for drugs analysis in biological fluids

Chaves, Andréa Rodrigues; Queiroz, Maria Eugênia Costa
2008-01-01

Resumo em inglês A novel solventless sample preparation, stir-bar sorptive extraction (SBSE), for extraction, and sample enrichment of organic compounds from biological fluids, is described in this manuscript from principle to applications. The SBSE is based on sorptive extraction, whereby the compounds are extracted into a polymer coating, polydimethylsiloxane (PDMS), on a magnetic stirring rod. The extraction is controlled by the partitioning coefficient of drugs between the PDMS and sa (mais) mple matrix, and upon the sample-extraction medium phase ratio. The SBSE technique has been applied successfully, with high sensitivities, to biomedical analysis of volatiles and for semi-volatiles drugs from biological sample, including urine, plasma, and saliva. SBSE combined with in situ derivatization, drugs quite more polar (e.g. metabolites) also can be analyzed.

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18

Estudo de recuperação de glifosato e AMPA derivados em solo utilizando-se resinas nacionais/ Study of recovery and stability of derivatized gliphosate and AMPA in soil using national resins

Souza, Tomaz Alves de; Matta, Marcia Helena de Rizzo da; Montagner, Émerson; Abreu, Adley Bergson Gonçalves de
2006-12-01

Resumo em inglês In the present paper we studied the recoveries of glyphosate, N-(phosphonomethyl)glycine (GLY) and its major metabolite, (aminomethyl)phosphonic acid (AMPA) in soil using national (Brazilian) ion-exchange resins, derivatization by a mixture of trifluoroacetic anhydride and trifluoroethanol and analyses by GC-MS. The quantification limits were 12 ng.g-1 for both compounds and the methodology showed a range of recuperation from 85 to 94% with coefficients of variation (CV) (mais) ranging from 4.07 to 6.91% for GLY. For AMPA, the mean recoveries ranged from 87 to 102% with CVs ranging from 5.81 to 6.99%. Additional studies showed that, due to the instability of the derivatized compounds, they must be analysed keeping constant time between derivatization and analysis, preferably less than 24 h.

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19

Eletroanálise de derivados acetaldeído com hidrazina e determinação em amostras de álcool combustível por voltametria de onda quadrada/ Electroanalysis of acetaldehyde derivatized with hydrazine and determination in fuel ethanol by square wave voltammetry

Rodgher, Vanessa S.; Stradiotto, Nelson R.; Zanoni, Maria Valnice B.; Barros, Aquiles A.
2006-07-01

Resumo em inglês A square wave voltammetric method is described for the determination of acetaldehyde using the derivatization reaction with hydrazine sulphate, based on the reduction of hydrazone generated as a product that exhibits a single well-defined peak at -1.19V in acetate buffer at pH 5. Calibration graphs were obtained from 1.0 x 10-6 mol L-1 to 10 x 10-6 mol L-1 of acetaldehyde, using a reaction time of 8 min and a hidrazine concentration of 0.02 mol L-1. The detection limit wa (mais) s 2.38 x 10-7 mol L-1. The method was applied satisfactorily to the determination of total aldehyde in fuel ethanol samples without any pre-treatment.

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20

Determinação simultânea de precursores de serotonina - triptofano e 5-hidroxitriptofano - em café/ Simultaneous determination of serotonin precursors - tryptophan and 5-hidroxytryptophan - in coffee

Martins, Ana Carolina C. L.; Silva, Tarliane M.; Gloria, M. Beatriz A.
2010-01-01

Resumo em inglês Epidemiological studies attributed positive effects in the central nervous system (CNS) to coffee. Among possible active constituents, serotonin, a neurotransmitter in the CNS, is present; but dietary sources do not cross the blood-brain barrier. Tryptophan and 5-hidroxytryptophan (5-HTP) are serotonin precursors and can affect brain concentrations. An ion-pair-HPLC, post-column derivatization with o-phthalaldehyde and fluorimetric detection before and after hydrolysis wi (mais) th NaOH and extraction with methanol:water was developed for the simultaneous determination of these compounds. It was selective, sensitive (LOD = 0.3 and 0.2 μg/mL), precise (91.3 and 94.2% recovery for tryptophan and 5-HTP, respectively), and linear from 0.3 to 40 μg/mL for both compounds. It was applied to green and roasted arabica and robusta coffees.

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21

Determinação de tricotecenos em cerveja e avaliação de incidência no produto comercializado no Rio Grande do Sul/ Determination of trichothecenes in beer and evaluation of occurence in the product commercialized in Rio Grande do Sul

Garda, Jaqueline; Macedo, Rejane Martins; Badiale-Furlong, Eliana
2004-12-01

Resumo em português Este trabalho adaptou um método e avaliou os seus indicadores de mérito para determinação de tricotecenos, desoxinivalenol (DON) e toxina T-2, em cervejas comercializadas na região Sul do Rio Grande do Sul, empregando cromatografia gasosa. As adaptações foram realizadas na etapa de extração, purificação, derivação e condições cromatográficas usando amostras de cerveja artificialmente contaminadas, avaliando a adequação do procedimento pela recuperação (mais) obtida. Foram estudados os solventes acetonitrila, metanol e cloreto de metileno puro ou em misturas para a etapa de extração. A purificação do extrato foi realizada empregando ou não minicoluna de carvão:alumina:celite (7:5:3). Para a derivação testou-se basicidade do meio (bicarbonato de sódio, piridina), agente acilante (TFAA e HFBI), tempo (30 e 60 minutos) e temperatura (60 e 80ºC). Foram otimizadas as condições cromatográficas em cromatógrafo gasoso equipado com injetor split/splitless e detector de ionização de chama. A melhor recuperação foi obtida quando se empregou partição líquido-líquido com cloreto de metileno, seguida da limpeza em minicoluna e derivação com TFAA e piridina a 60°C durante 60 minutos. A recuperação média foi de 83 e 103% para DON e toxina T-2 respectivamente, para níveis de adição entre 50 e 200ng/mL. O coeficiente de variação assumiu valores de 2% e 4% e limite de detecção de 21 e 60 ng/mL. A aplicabilidade do método foi testada em um levantamento realizado em 72 amostras de cervejas. Destas 9,7% estavam contaminadas, sendo 5,3% com DON (50 a 336ng/mL) e 4,5% com toxina T-2 (114 a 249ng/mL). Resumo em inglês The present work adapted and evaluated a trichothecenes determination, DON and the T-2 toxin and conduted a survey of the product commercialized in Rio Grande do Sul in beer commercialized in Rio Grande do Sul State by gas chromatography. It studied extraction, purification, derivatization and chromatographic conditions using artificially contaminated samples. Acetonitrile, methylene chloride and methanol pure or in misture were tested for the extraction step. The extract (mais) was purified using a carbon:alumina:celite minicolumn (7:5:3). For derivatization, the following conditions were tested: the basicity of the medium (sodioum bicarbonate, pyridine),the derivatizing agent (TFAA and HFBI), reaction time (30 and 60 minutes) and temperature (60 and 80°C). The chromatographic conditions were optimized in a gas chromatograph, with a split/splitless injector and an ionization flame detector. The highest recovery was obtained when liquid-liquid partition was carried out with methylene chloride, followed by cleaning in a minicolumn and derivatization with TFAA and pyridine at a temperature of 60°C for 60 minutes. The average recovery for DON and the T-2 toxin were 83 and 103%, the coefficient variation 1.6 to 4% and the detection limit of 21 and 60ng/mL, respectively. The applicability of the method was tested in a survey carried out in 72 beer samples, 9.7 % of which were contaminated 5.3% with DON (50 to 336ng/mL) and 4.5% with the T-2 toxin (114 to 249ng/mL).

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Determinação de esteróides androgênicos anabólicos em urina por cromatografia gasosa acoplada à espectrometria de massas/ Detection of androgenic anabolic steroids (AAS) in urine samples by gas chromatography-mass spectrometry

Campos, Daniel Rossi de; Yonamine, Mauricio; Alves, Maria Janieire de Nazaré Nunes; Moreau, Regina Lucia de Moraes
2005-12-01

Resumo em português Esteróides androgênicos anabólicos (EAA) são substâncias naturais, sintéticas ou semi-sintéticas derivadas da testosterona, utilizadas em atividades esportivas com o objetivo de melhorar o desempenho físico pelo aumento de massa e força muscular. Apesar de causarem efeitos tóxicos graves, principalmente sobre os sistemas cardiovascular, hepático e neuro-endócrino, os EAA têm sido amplamente utilizados no âmbito esportivo. Desta forma, o presente trabalho tev (mais) e como objetivo a validação de um método para a determinação de esteróides e/ou seus produtos de biotransformação em amostras de urina por cromatografia gasosa acoplada à espectrometria de massas (CG-EM). O método baseou-se na hidrólise enzimática de esteróides conjugados, no emprego da extração líquido-líquido e na derivação do extrato para posterior análise por CG-EM, no modo de monitoramento seletivo de íons (SIM). O método validado cumpriu com os princípios de confiança necessários para a determinação de EAA em amostras de urina com a finalidade de controle de dopagem no esporte. Os limites de detecção dos esteróides analizados variaram de 0,5 a 15 ng/mL. Bons valores de precisão (intra e interensaio) também foram obtidos (CV Resumo em inglês Androgenic anabolic steroids (AAS) are defined as natural, synthetic or semi-synthetic drugs chemically derived from testosterone, used with the aim to improve physical performance by increasing both muscle strength and mass. Despite their reported toxicological effects on the cardiovascular, hepatic and neuro-endocrine systems, the AAS have been extensively used in sports activities. The objective of this study was to validate an analytical method for the detection of AA (mais) S and/or their metabolites in urine samples. The method was based on enzymatic hydrolysis, liquid-liquid extraction, derivatization and further analysis by gas chromatography-mass spectrometry (GC-MS) operated in the selected ion monitoring mode (SIM). The validated method agrees with the confidence concepts for AAS detection in urine samples for anti-doping control programs. The limits of detection of AAS varied from 0,5 to 15ng/mL. Good inter and intra-assay precisions were also observed (CV

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Determinação de efedrinas em urina por cromatografia em fase gasosa (CG/DNP) para o controle da dopagem no esporte/ Gas chromatographic method for the determination of ephedrines in urine for doping control purposes

Garcia, Paula Rodrigues; Yonamine, Mauricio; Moreau, Regina Lúcia de Moraes
2005-09-01

Resumo em português Efedrinas são aminas simpatomiméticas componentes de diversas especialidades farmacêuticas, utilizadas no tratamento de doenças respiratórias devido à sua ação descongestionante e broncodilatora. Atualmente, diversos produtos comercializados como suplementos nutricionais contêm efedrinas e são amplamente utilizados no meio esportivo, com o objetivo de facilitar a queima de gorduras e melhorar o desempenho. Entretanto, o uso indiscriminado destas substâncias pod (mais) e acarretar série de efeitos tóxicos como hipertensão, taquicardia, cefaléia e tremores. Devido à sua ação psicoestimulante, foram incluídas na lista de substâncias proibidas nas atividades esportivas pelo Comitê Olímpico Internacional (COI) e estabelecidas concentrações na urina para o controle da dopagem (efedrina e metilefedrina: 10 µg/mL). O presente trabalho teve como objetivo a validação de um método para quantificação de efedrinas, por cromatografia em fase gasosa acoplada a detetor de nitrogênio/fósforo (CG/DNP), em amostras de urina com a finalidade de controle da dopagem. O método consistiu em extração líquido-líquido e posterior derivação das efedrinas com anidrido trifluoroacético, e demonstrou ser simples e prático, apresentando linearidade nas faixas de concentração estudadas. Amostras de urina de voluntários que relataram uso de efedrinas foram submetidas à análise pelo método proposto. Resumo em inglês Ephedrines are sympathomimetic amines present in many pharmaceutical preparations used in the treatment of respiratory diseases due to their actions against broncospasm and congestion. Nowadays, several products sold as nutritional supplements contain ephedrines and are widely used in a diverse range of sports as weight loss aids and enhancement of athletic performance. However, the abuse of ephedrines may lead to a number of adverse effects including hypertension, headac (mais) he, tachycardia and seizure. Due to their CNS stimulating action, ephedrines are included in the prohibited list of substances by the International Olympic Committee (IOC). Urinary threshold concentrations were established (ephedrine and methylephedrine >10 µg/mL). The aim of this work was to develop and validate a method for the simultaneous determination of ephedrines present in urine samples for doping purposes by gas chromatography with nitrogenous-phosphorous detector (GC/NPD). The method was based on a liquid-liquid extraction of alkalinized urine and further derivatization with trifluoroacetic anhydride (TFA). The validated method showed to be simple, practical and linear at the studied concentrations range. Urine samples collected from volunteers, who reported the use of ephedrines, were submitted to the proposed method.

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Desenvolvimento e validação de um método analítico para a determinação de histamina em vinhos utilizando cromatografia líquida de alta eficiência com detecção por fluorescência/ Development and validation of an analytical method for the determination of histamine in wines using high performance liquid chromatography with fluorescence detection

Prestes, Osmar D.; Presta, Michele A.; Kolberg, Diana I. S.; Zanella, Renato; Rossato, Simone B.; Penna, Neidi G.; Hecktheuer, Luisa H. R.
2007-02-01

Resumo em inglês A rapid and efficient method for the analysis of histamine in wines using HPLC with fluorescence detection after derivatization was developed and validated. The method LOD and LOQ values were 0.25 and 0.50 mg L-1 respectively. The repeatability and intermediary precision for the instrument and for the method presented RSD values of 3.7 and 2.9%, and 6.0 and 5.6%, respectively. The recoveries were 95.5 and 89.9% for the fortification levels of 2 and 10 mg L-1. The method w (mais) as applied to determine the histamine content in Cabernet Sauvignon wines, which presented values between 1.2 and 5.7 mg L-1.

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Desenvolvimento e validação de método de análise de glifosato em grãos de soja/ Development and validation of a method of analysis of glyphosate in soy grains

Abreu, Adley Bergson Gonçalves de; Matta, Marcia Helena de Rizzo da; Montagner, Émerson
2008-01-01

Resumo em inglês The main objective of this work is to develop an efficient procedure to determine glyphosate in soybean grains. The cleanup of the aqueous extracts was done in two steps, beginning with liquid-liquid partitioning and then solid-phase extraction with anion exchange resin. After derivatization with a mixture of trifluoroacetic anhydride (TFAA) and trifluoroethanol (TFE), quantification was done by gas chromatography coupled to mass spectrometry. The mean recovery and RSD of (mais) the spiked samples were, respectively, 80.5% and 3.1% at level 0.200 mg kg-1, 93.3% and 18.7% at level 0.500 mg kg-1 and 92% and 3.5% at level 1.000 mg kg-1. The method was linear in the working range (correlation coefficient = 0.9965).

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Desenvolvimento de metodologia para determinação de 4-cloroanilina em frangos por cromatografia gasosa - espectrometria de massas: análise em tecidos tratados com digluconato de clorhexidina após o processamento térmico/ Methodology for 4-chloroaniline determination in poultry by GC-MS: analisys in chlorhexidine digluconate treated tissues after termical processing

Vicente, Eduardo; Toledo, Maria Cecília de Figueiredo
2003-12-01

Resumo em português A degradação do antimicrobiano digluconato de clorhexidina (DGCH) durante armazenamento ou processamento térmico pode formar a 4-cloroanilina (CA), um composto potencialmente carcinogênico. Conseqüentemente, o uso deste sanitizante para descontaminação de carcaças de frangos representa uma fonte de risco para o consumidor, devendo ser avaliada a presença da CA no produto tratado. Um método foi desenvolvido para determinação de resíduos de CA em tecidos de fra (mais) ngos. Após a extração com diclorometano, foi feita a limpeza do extrato em cartucho C18 e quantificação por cromatografia gasosa-espectrometria de massas (CG-EM), sem derivação. A recuperação média (89,2% - CV 9,9%.) e o limite de detecção (1,8ng/g) foram considerados satisfatórios para os propósitos do estudo. Em amostras tratadas com DGCH e não submetidas a processamento térmico, a quantidade de CA detectada foi relativamente baixa, e provavelmente se originou da solução de tratamento. A fritura e a cocção em forno convencional resultaram em níveis elevados de CA, enquanto que a cocção em panela de pressão não alterou os níveis de CA presentes na amostra crua. Em vista destes resultados e, considerando-se o potencial tóxico da CA, recomenda-se que estes dados sejam levados em consideração quando avaliada a utilização de DGCH como sanitizante de carcaças em abatedouros de aves. Resumo em inglês The degradation of the antimicrobial agent chlorhexidine digluconate (CHDG) during storage or thermal process originates 4-chloroaniline (CA), a compound which is potentially carcinogenic. As the use of this sanitizing agent to decontaminate poultry carcasses in processing plants may represent a risk to the consumers, it is important to search for the presence of CA residues in the treated products. A method was developed to quantify CA in poultry tissues. After dichlorom (mais) ethane extraction, the extract was cleaned on a C18 cartridge and the quantitation was performed, without derivatization, by gas chromatography-mass spectrometry (GC-MS). The mean recovery (89.2% - CV 9.9% ) and detection limit (1.8ng/g), were satisfactory for the purposes of the study. Analysis of samples treated with CHDG, before thermal processing, resulted in low CA levels, which probably originated from the treating solution. Frying and cooking in conventional oven resulted in relatively higher levels of CA, while cooking under pressure did not change the residual levels when compared to the raw samples. In view of these results and taking into consideration the toxic potential of CA, the data generated by this study should be considered in the case of use of chlorhexidine as poultry carcasses sanitizing agent.

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Cafeína: revisão sobre métodos de análise/ Analytical methods for caffeine

De Maria, Carlos A. B.; Moreira, Ricardo F. A.
2007-02-01

Resumo em inglês Gravimetric and Bailey-Andrew methods are tedious and provide inflated results. Spectrofotometry is adequate for caffeine analysis but is lengthy. Gas chromatography also is applied to the caffeine analysis but derivatization is needed. High performance liquid chromatography with ultraviolet detection (HPLC-UV) and reversed phase is simple and rapid for xanthine multianalysis. In HPLC-UV-gel permeation, organic solvents are not used. HPLC-mass spectrometry provides an une (mais) quivocal structural identification of xanthines. Capillary electrophoresis is fast and the solvent consumption is smaller than in HPLC. Chemometric methods offer an effective means for chemical data handling in multivariate analysis. Infrared spectroscopy alone or associated with chemometries could predict the caffeine content in a very accurate form. Electroanalytical methods are considered of low cost and easy application in caffeine analysis.

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Avaliação quantitativa de monoepoxiácidos, monocetoácidos e monohidroxiácidos em óleos e gorduras provenientes de fritura descontínua de batatas/ Quantitative evaluation of monoepoxyacids, monoketoacids and monohydroxyacids in fats and oils used in discontinuous frying of potatoes

Machado, Eliana Rodrigues; Marmesat, Susana; Dobarganes, María del Carmen; Abrantes, Shirley
2008-09-01

Resumo em português Na fritura, os óleos e gorduras sofrem degradação formando os compostos polares, como os triacilgliceróis polimerizados e os monômeros de triacilgliceróis oxidados, estes últimos têm sido relacionados a patologias e se constituem de grupos como os monoepoxiácidos, monocetoácidos e monohidroxiácidos. Foram determinados os teores destes três grupos de substâncias, através da análise cromatográfica a gás dos ésteres metílicos de ácidos graxos após deriva (mais) ção a frio das amostras e concentração posterior das substâncias de interesse mediante extração em fase sólida, e os teores dos ácidos graxos polares polimerizados, utilizando a combinação das técnicas cromatográficas de adsorção em coluna e por exclusão, em gordura de soja parcialmente hidrogenada e óleos de soja e de palma, aquecidos a 180 °C por 25 horas, provenientes de experimentos de fritura. Foram encontrados teores de 3,30 a 8,24; 1,51 a 4,32 e 3,42 a 8,71 mg.g-1 de monoepoxiácidos, monocetoácidos e monohidroxiácidos, respectivamente, nas amostras com níveis de compostos polares de 20,8 a 44,1% (m/m), e predominância de formação de polímeros. Os resultados sugeriram que óleos e gorduras monoinsaturados apresentam maior tendência à formação de monômeros oxidados e menor tendência à formação de polímeros, ao contrário dos óleos poliinsaturados. Resumo em inglês During frying, fats and oils undergo degradation with the formation of polar compounds. Among these are polymeric triglycerides, as well as oxidized monomeric triglycerides. The last group has been related to several diseases and contains groups including epoxy, keto and hydroxy groups of importance from a quantitative point of view. In this study, monoepoxyacids, monoketoacids and monohydroxyacids were quantified in partially hydrogenated soybean oil, soybean oil and pal (mais) m oil, after heating for 25 hours, at 180 °C, in frying experiments. The determination was carried out by gas chromatography after fat derivatization to fatty acid methyl esters at room temperature and concentration of the compounds of interest by solid phase extraction on silica cartridges. Quantitative analyses of polar fatty acids were also obtained by combination of adsorption and size exclusion chromatography. The major content corresponded to polymeric compounds. Amounts ranging from 3.30 to 8.24; from 1.51 to 4.32 and from 3.42 to 8.71 mg.g-1 were found for monoepoxyacids, monoketoacids and monohydroxyacids, respectively, for samples containing polar compounds between 20.8 and 44.1%. The results suggested that monounsaturated oils have a higher tendency to the formation of oxidized monomers while polyunsaturated oils have a higher tendency to the formation of polymers.

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Avaliação da estabilidade do marcador plasmático do estresse oxidativo: malondialdeído/ Evaluation of the stability of the oxidative stress plasmatic biomarker: malondialdehyde

Grotto, Denise; Valentini, Juliana; Boeira, Silvana; Paniz, Clóvis; Maria, Lucas Santa; Vicentini, Juliana; Moro, Angela; Charão, Mariele; Garcia, Solange Cristina; Cardoso, Simone Gonçalves
2008-01-01

Resumo em inglês Malondialdehyde (MDA) is one of the lipid peroxidation products widely used as indicator of cellular injury. However, the short-term and the long-term stability of this biomarker remain unclear. The objective of this work was to evaluate the stability of plasmatic MDA at -20 ºC, utilizing thiobarbituric acid (TBA) as derivative in spectrophotometric and chromatographic analysis. The results showed that MDA was stable for 24 h after blood collection, was not stable when s (mais) tored after alkaline hydrolysis, remained stable for 30 days after TBA derivatization and was stable for 3 days when stored after n-butanol extraction, all at -20 ºC.

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Aplicação e avanços da espectroscopia de luminescência em análises farmacêuticas/ Application and advances in the luminescence spectroscopy in pharmaceutical analyses

Sotomayor, Maria D. P. T.; Dias, Iara Lúcia T.; Lanza, Marcos R. V.; Moreira, Altair B.; Kubota, Lauro T.
2008-01-01

Resumo em inglês This paper provides a review on the latest advances and applications of the luminescence spectroscopy for the development of pharmaceuticals analyses methods, basically based on the photo- and chemiluminescence. The different forms of the drugs determination on pharmaceuticals through the fluorescence and chemiluminescence are discussed. The analyses include the drugs native fluorescence (liquid and solid-phases); the fluorescence from the oxidizing or reducing forms of t (mais) he drug; the fluorescence from the chemical derivatization and their photochemistry and hydrolysis reactions. The quenching of luminescence and chemiluminescence generation for the pharmaceutical quantification are also shown. Finally, the trends and future perspectives of the luminescence spectroscopy in the field of the pharmaceutical research are discussed.

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Alternativa analítica para especiação físico-química de mercúrio em águas costeiras tropicais/ Analytical alternative for the physical-chemical speciation of mercury in tropical coastal waters

Marins, Rozane V.; Paraquetti, Heloísa Helena M.; Ayres, Gisele A.
2002-05-01

Resumo em inglês The determination of the physical-chemical mercury speciation in tropical coastal waters using the derivatization technique with CVAFS detection was optimized. This methodology is able to separate the elementary, reactive, organic and total mercury phases with low operational costs. The importance of bromide chloride solution, the diluted aqua regia, used as the oxidative solution, and different compositions of the reductive solution of stannous chloride were tested and t (mais) he better results for coastal waters are presented. The recuperation of the sum of the different phases ranges from 80 to 94% of the total Hg content in duplicates of different marine samples. The optimized methodology permits important studies on the mercury cycle in the coastal environment.

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Alendronato de sódio: metodologias para análise quantitativa/ Sodium alendronate: methods for analytical quantitation

Ribeiro, Ana Ferreira; Volpato, Nadia Maria
2005-10-01

Resumo em inglês This paper presents a review of some published proposals for the analysis of sodium alendronate. The drug is an aminobisphosphonate compound used to inhibit the osteoclastic resorption of bone, and different methods were developed for its quantitative determination. These methodologies employed reversed-phase or ion-exchange HPLC analysis, both associated with different detectors: UV and fluorescence detection after derivatization of the drug, conductivity and refractive (mais) index detectors, as well as the indirect UV detection. Titrimetry and spectrophotometry (with previous complexation of the drug), which are simpler procedures, were also described, but they showed poor specificity when compared to liquid chromatography.

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