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Search Results: 1 - 10 of 35323 matches for " Flaviano Oliveira;Neves "
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Evaluation of pesticide adsorption in gas chromatographic injector and column
Pinho, Gevany Paulino de;Silvério, Flaviano Oliveira;Neves, Ant?nio Augusto;Queiroz, Maria Eliana Lopes Ribeiro de;
Química Nova , 2012, DOI: 10.1590/S0100-40422012000400016
Abstract: components in complex matrices can cause variations in chromatographic response during analysis of pesticides by gas chromatography. these variations are related to the competition between analytes and matrix components for adsorption sites in the chromatographic system. the capacity of the pesticides chlorpyrifos and deltamethrin to be adsorbed in the injector and chromatographic column was evaluated by constructing three isotherms and changing the column heating rate to 10 and 30 oc min-1. by using ancova to compare the slope of calibration graphs, results showed that the higher the injector temperature (310 oc) the lower the pesticide adsorption. also, deltamethrin influenced the adsorption of chlorpyrifos on the column chromatographic.
Influência dos constituintes químicos dos extratos de diferentes matrizes na resposta cromatográfica de agrotóxicos
Pinho, Gevany Paulino de;Silvério, Flaviano Oliveira;Neves, Ant?nio Augusto;Queiroz, Maria Eliana L. R.;Starling, Maria Ant?nia V. M.;
Química Nova , 2010, DOI: 10.1590/S0100-40422010000400028
Abstract: multiresidue methods for pesticides monitoring by gc are commonly employed, however, it is well known that the presence of compounds of the matrix introduces errors during the quanti?cation. the main consequence of matrix effect is an increasing or decreasing analyte signal after the gc saturation with extracts of matrix. in this paper, the influence of constituents of nine matrices on the quantification of the four pesticides by gc-ecd was studied. variation of signal was evaluated by pca and hca, and results showed that the constituents of tomato increased the signal (until 300%), while extracts of apple decreased (until -20%). variation the analyte signal in the presence of the matrix in respect to the same analyte in solvent (standard solution) also was observed, mainly for liver extract (until 270%).
Effect of the trehalose levels on the screening of yeast as probiotic by in vivo and in vitro assays
Martins, Flaviano S.;Miranda, Ieso C.;Rosa, Carlos A.;Nicoli, Jacques R.;Neves, Maria J.;
Brazilian Journal of Microbiology , 2008, DOI: 10.1590/S1517-83822008000100012
Abstract: probiotics are viable defined microorganisms (bacteria or yeasts) that exert a beneficial effect on the health of the host when ingested in adequate amounts. screening for such biotherapeutic agents is commonly performed by in vitro assays simulating gastrointestinal environment to determine the ability to survive in the digestive tract. in the present study, the possibility of extrapolation of data obtained in in vitro assays to in vivo conditions was studied using five saccharomyces cerevisiae strains isolated from brazilian atlantic rain forest. trehalose contents and survival after exposure to a combination of physiological stresses generally found in the gastrointestinal tract of humans were determined for the five yeasts and compared to the behavior of saccharomyces boulardii, a well-known probiotic. the results were completed with the colonization capacity of the gastrointestinal tract of gnotobiotic mice by these yeast strains. some results obtained by in vitro assays are not confirmed by in vivo experiments, indicating that the extrapolation cannot be always done.
Efeito de matriz na quantifica??o de agrotóxicos por cromatografia gasosa
Pinho, Gevany P.;Neves, Ant?nio A.;Queiroz, Maria Eliana L. R.;Silvério, Flaviano O.;
Química Nova , 2009, DOI: 10.1590/S0100-40422009000400030
Abstract: the lack of accuracy of a chromatographic method can be associated with the matrix effect. this effect is observed in pesticide quantification by gas chromatography when the chromatographic signals of standards prepared in solvents are compared with those of the analyte in extracts of complex matrices. in the competition between the matrix components and the pesticides for the active sites of the liner, a larger amount of pesticides is transferred to the column, giving apparent extractions above 100%. in this work, we discuss factors that contribute to the matrix effect and present some attempts to overcome the problem.
Study of the Reaction Derivatization Glyphosate and Aminomethylphosphonic Acid (AMPA) with N,O-Bis(trimethylsilyl)trifluoroacetamide  [PDF]
T. C. P. G. Catrinck, Maria Clara Santana Aguiar, Amanda Dias, Flaviano Oliveira Silvério, Paulo Henrique Fidêncio, Gevany Paulino de Pinho
American Journal of Analytical Chemistry (AJAC) , 2013, DOI: 10.4236/ajac.2013.411077
Abstract:

This work aimed to study the derivatization unprecedented of glyphosate and AMPA solutions using N,O-bis (trimethylsilyl)trifluoroacetamide (BSTFA) combined with trimethylchlorosilane (TMCS), evaluating the composition of the reaction medium, use of ultrasound, volume of BSTFA:pyridine and pH of the reaction medium. From this study it was inferred that the reaction medium was composed of BSTFA:pyridine in ratio 60:100, respectively, without ultrasonic vibration and pH adjustment that provide optimal conditions for analysis by GC-MS. Furthermore, the methodology used was simple and fast, and that was the most practical method commonly used.

A renda da terra e suas cambalhotas: uma discuss o sobre renda fundiária urbana, solo como mercadoria e a centralidade do Iguatemi
Margarete Rodrigues Neves Oliveira
Geotextos : Revista da Pós-Gradua??o em Geografia da Universidade Federal da Bahia , 2008,
Abstract: Este artigo analisa o processo de produ o do mais novo centro de negócios de Salvador - a centralidade da área do Iguatemi. Valendo-se de uma discuss o teórica sobre a renda da terra, este trabalho utiliza categorias de análise que possibilitam desvendar o processo de valoriza o de trechos do solo urbano nessa cidade. Partindo da interpreta o de dados oriundos de projetos de planejamento municipal, estatísticas, legisla o de uso do solo, notícias da imprensa, este trabalho mostra que essa centralidade surgiu como resultado de um sistema integrado de a es de diferentes agentes governamentais e privados nos últimos 40 anos. O artigo revela que por trás de discursos oficiais de desenvolvimento urbano e de políticas governamentais de planejamento, desenvolveram-se agendas e práticas de um planejamento urbano invisível, que alocou recursos e materializou trabalho numa por o .solo virgem. da cidade do Salvador. Este processo resultou na eleva o do valor da renda fundiária dessa área, o que atendeu a interesses privados. Este estudo configura-se num esfor o de tornar o invisível visível e fornece algumas bases para o uso de novos e alternativos modelos de interpreta o da produ o do espa o urbano.
Influence of tomato components in the quantification of four pesticides by gas chromatography
Pinho, Gevany P.;Neves, Ant?nio A.;Queiroz, Maria Eliana L. R.;Silvério, Flaviano O.;Marthe, Deyse B.;
Journal of the Brazilian Chemical Society , 2012, DOI: 10.1590/S0103-50532012000200015
Abstract: the matrix effect in gas chromatographic analysis is attributed to the presence of coextractives in organic phase obtained in the extraction process. this work reports the quantification study of increased chromatographic response of four pesticides in organic extracts of tomato extracted by solid-liquid extraction with low temperature purification (sle-ltp). the pesticides chlorpyrifos, λ-cyhalothrin, cypermethrin and deltamethrin showed an increased chromatographic response after the saturation of the chromatographic system with multiple injections of organic extracts of tomato. it was also found that the greater the retention time, the greater the matrix effect, and that the internal standard reduces the matrix effect but does not eliminate it. the matrix effect measured by the analytical curves (in acetonitrile and matrix extract) was 27% for chlorpyrifos, 46% for λ-cyhalothrin, 96% for cypermethrin and 180% for deltamethrin.
A HIGH YIELD SYNTHESIS OF 1,2:5,6-DI-O-ISOPROPYLIDENE-D-MANNITOL
ALVARENGA,ELSON SANTIAGO DE; TEIXEIRA CARNEIRO,V?NIA MARIA; OLIVEIRA SILVéRIO,FLAVIANO; ARGOLO SALIBA,WILLIAM;
Journal of the Chilean Chemical Society , 2006, DOI: 10.4067/S0717-97072006000300013
Abstract: a high yield synthesis of 1,2:5,6-di-o-isopropylidene-d-mannitol: a great improvement in the synthesis of 1,2:5,6-di-o-isopropylidene-d-mannitol (2) using d-mannitol (1) as starting material, is described. the acetalation of (1) was performed in acetone in the presence of zinc chloride as catalyst to give (2) in 87% yield. some studies on the acetal stability were carried out to explain the high yields. high field nmr spectra were obtained and assignment of all signals was accomplished with the aid of double irradiation, difference noe and hetcor spectra
A pirólise como técnica analítica
Silvério, Flaviano Oliveira;Barbosa, Luiz Cláudio Almeida;Piló-Veloso, Dorila;
Química Nova , 2008, DOI: 10.1590/S0100-40422008000600045
Abstract: in this paper historical aspects of analytical pyrolysis, the equipment used, the fundamentals and the mechanisms of pyrolysis of different polymeric materials are discussed. the latest work on analytical pyrolysis applied to various types of synthetic and natural samples is reviewed. current applications of this technique that are discussed include identification of microorganisms, analysis of trace compounds by forensic laboratories, investigation of food and agricultural products, study of the chemical composition of wood, authentication and conservation of artworks, and the study of environmental and geochemical samples.
A HIGH YIELD SYNTHESIS OF 1,2:5,6-DI-O-ISOPROPYLIDENE-D-MANNITOL
ELSON SANTIAGO DE ALVARENGA,V?NIA MARIA TEIXEIRA CARNEIRO,FLAVIANO OLIVEIRA SILVéRIO,WILLIAM ARGOLO SALIBA
Journal of the Chilean Chemical Society , 2006,
Abstract: A HIGH YIELD SYNTHESIS OF 1,2:5,6-DI-O-ISOPROPYLIDENE-D-MANNITOL: A great improvement in the synthesis of 1,2:5,6-di-O-isopropylidene-D-mannitol (2) using D-mannitol (1) as starting material, is described. The acetalation of (1) was performed in acetone in the presence of zinc chloride as catalyst to give (2) in 87% yield. Some studies on the acetal stability were carried out to explain the high yields. High field NMR spectra were obtained and assignment of all signals was accomplished with the aid of double irradiation, difference NOE and HETCOR spectra
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