Determinação de paclobutrazol em manga por cromatografia líquida de alta eficiência.

Este trabalho descreve um método para determinação de paclobutrazol em amostras de manga. A extração foi feita em metanol e as análises por cromatografia líquida de alta eficiência (CLAE), usando coluna de fase-reversa, C-18, fase móvel metanol/água 60:40, v/v, detecção e quantificação a 220 nm. Os seguintes parâmetros de validação foram obtidos: limite de detecção do método de 0,025 mg kg-1, limite de quantificação do método de 0,050 mg kg-1, linearidade de 0,100?5,00 mg L-1 (r2? 0,9994); recuperação de 82 a 92%, precisão intermediária (%RSD) < 12%, para paclobutrazol. O método mostrou ser simples, eficiente e confiável para a determinação de resíduos de paclobutrazol em amostras de manga.

Aplicação do método QuEChERS na análise de agrotóxicos em uva in natura por cromatografia líquida acoplada à espectrometraia de massas em tandem (LC-MS-MS).

2008

Degradação de picloram em águas utilizando o reagente de fenton e monitoramento por cromatografia líquida.

2008

Degradação de glifosato por fotocatálise heterogênea utilizando filmes finos de TiO2 suportados em anéis de quartzo seguida de análise por cromatografia líquida com detecção por fluorescência.

2006

ESTUDO DA PREPARAÇÃO DOS EXTRATOS DE PRÓPOLIS E SUAS APLICAÇÕES

Ethanolic extracts from propolis were performed by using lhe water and vaflous coneentrations of etanol as solvent. The extracts were investigated by measurement of absorption spectruin with Uv-spectrophotometer (UV-scanning), reversed phase-high performance thin-layer chromatography, Reversed phase-HPLC. Maximum absorption of ali extracts was 290 nm, resembling flavonoid compounds and 80% ethanolic extract showed highest absorption at 290 nm. The most isosakuranetin, quercefin, and kaempferol were extracted from mixtures of propolis and 60% etanol, whereas 70% etanol extracted te most pinocembrin and sakuranetin, but 80% etanol extracted more kaempferide, acacetin, and isorhamnetin from propolis. The 60 to 80% ethanolic extracts ofpropolis inhibited highly to microbial growth and 70 and 80% ethanolic extracts showed lhe greatest antioxidant activity and 80% ethanolic extract inhibited highly to hyaluronidase activity.

TEOR DE CAFEÍNA EM CAFÉS BRASILEIROS

Different brands and batches of brazilian regular and instant coffee were purchased in supermarkets of Campinas? city and analysed for caffeine content. The method used involved extraction with boiling water, clarification with saturated basic acetate and determination by high performance liquid cromatography. Analysis was carried out using a Model 6000 A solvent delivery system (Waters associates), and a Model 7125 sample injector system (Reodyne, Inc.) with a 5µl sample loop. The system was also equipped with a Waters Model M440 absorbance detector set at 254 nm. A Merck ODS 5µm column (15 cm x 4.6 mm i.d.) was used to separate the caffeine. The mobile phase was methanol:water (25:75, v/v). The caffeine content varied for different brands and types of coffee and according to the beverage preparation technique. Values in the range of 0.43 to 0.85 mg/ml and 0.61 to 0.82 mg/ml were determined in regular and instant coffee, respectively.

Determinação de substitutos da manteiga de cacau em coberturas de chocolate através da análise de triacilgliceróis

Brazilian regulations prohibit the addition of cocoa butter replacements to chocolate, in total or partial substitution. The objective of the present work was to check the quality standards of four of coating bitter Brasilian chocolate bars and five of coating milk chocolate bars, commercialized in Campinas. In order to check the possible addition of substitutes, the triacylglycerol composition was determined, and the results were analysed by Padley & Timms mathematical method. The triacylglycerol composition of each sample was determined by high temperature gas chromatography (HTGC). The presence of cocoa butter replacements was not detected in the brands of coating chocolate.

Hidrocarbonetos aromáticos policíclicos em margarina, creme vegetal e maionese

Polycyclic aromatic hydrocarbons (PAHs) are a group of compounds that have been the subject of much concern due to their toxic potential. In this study, margarine?s, vegetable cream and mayonnaise available on the Brazilian market were analyzed for pyrene, chrysene, benzo(a)pyrene, benzo(b)fluoranthene and dibenzo(a,h)anthracene. The analytical methodology involved liquid-liquid extraction, clean-up on silica gel column and determination by high performance liquid chromatography using fluorescence detector. Variable levels of contamination were found within differents brands of the same product and within differents batches of the same brand. The total PAH content was in the range of 4.1 to 7.1mug/kg in vegetable cream, 1.7 to 3.9mug/kg in margarine and 1.0 to 21.7mug/kg in mayonnaise. In general the products which according to the label contain corn oil showed the highest levels of contamination. Based on these results and on the importance of fat, oils and derived products for the intake of PAHs, it is recommended that producers of margarine, vegetable creams and mayonnaise start to control the contamination of the vegetable oils used in the elaboration of these products, in order to reduce the exposure of consumers to excessive amounts of potentially carcinogenic compounds.

A method to determine volatile contaminants in polyethylene terephthalate (PET) packages by HDC-GC-FID and its application to post-consumer materials

A simple and low cost method to determine volatile contaminants in post-consumer recycled PET flakes was developed and validated by Headspace Dynamic Concentration and Gas Chromatography-Flame Ionization Detection (HDC-GC-FID). The analytical parameters evaluated by using surrogates include: correlation coefficient, detection limit, quantification limit, accuracy, intra-assay precision, and inter-assay precision. In order to compare the efficiency of the proposed method to recognized automated techniques, post-consumer PET packaging samples collected in Brazil were used. GC-MS was used to confirm the identity of the substances identified in the PET packaging. Some of the identified contaminants were estimated in the post-consumer material at concentrations higher than 220 ng.g-1. The findings in this work corroborate data available in the scientific literature pointing out the suitability of the proposed analytical method.

Determinação de aflatoxina B1 em rações e aflatoxina M1 no leite de propriedades do Estado de São Paulo

A ocorrência de aflatoxina B1 (AFB1) em rações e aflatoxina M1 (AFM1) no leite cru foi avaliada em propriedades leiteiras situadas na região nordeste do Estado de São Paulo, Brasil, de outubro de 2005 a fevereiro de 2006. A análise de aflatoxinas foi efetuada utilizando-se colunas de imunoafinidade para purificação dos extratos, sendo a quantificação realizada através de cromatografia líquida de alta eficiência. A AFB1 foi detectada em 40% das rações em níveis de 1,0 a 19,5 μg.kg-1. A concentração de AFM1 em 36,7% de amostras de leite positivas variou de 0,010 a 0,645 μg.L-1. Somente uma amostra de leite estava acima do limite de tolerância adotado no Brasil (0,5 μg.L-1) para AFM1. Concluiu-se que as concentrações de aflatoxinas na ração e no leite foram relativamente baixas, embora a alta frequência das aflatoxinas nas amostras analisadas indique a necessidade de contínuo monitoramento a fim de prevenir a contaminação de ingredientes e rações destinadas ao gado leiteiro.

Critical applications of SW 846 US EPA methods to evaluation of marine samples quality

Technical evaluation of analytical data is of extreme relevance considering it can be used for comparisons with environmental quality standards and decision-making as related to the management of disposal of dredged sediments and the evaluation of salt and brackish water quality in accordance with CONAMA 357/05 Resolution. It is, therefore, essential that the project manager discusses the environmental agency's technical requirements with the laboratory contracted for the follow-up of the analysis underway and even with a view to possible re-analysis when anomalous data are identified. The main technical requirements are: (1) method quantitation limits (QLs) should fall below environmental standards; (2) analyses should be carried out in laboratories whose analytical scope is accredited by the National Institute of Metrology (INMETRO) or qualified or accepted by a licensing agency; (3) chain of custody should be provided in order to ensure sample traceability; (4) control charts should be provided to prove method performance; (5) certified reference material analysis or, if that is not available, matrix spike analysis, should be undertaken and (6) chromatograms should be included in the analytical report. Within this context and with a view to helping environmental managers in analytical report evaluation, this work has as objectives the discussion of the limitations of the application of SW 846 US EPA methods to marine samples, the consequences of having data based on method detection limits (MDL) and not sample quantitation limits (SQL), and present possible modifications of the principal method applied by laboratories in order to comply with environmental quality standards.

Effect of Potato virus X on total phenol and alkaloid contents in Datura stramonium leaves

The present paper reports results of the effect of Potato virus X (PVX) on the contents of total phenols and alkaloids in leaves of Datura stramonium. A significant decrease in the contents of phenols and alkaloids was observed in leaves inoculated with PVX (X-I). However, there was an increase in the percentage of phenols in leaves rubbed with phosphate buffer (C1-I) and in leaves from the nodes immediately above, possibly induced by mechanical injury. Gas chromatography/mass spectroscopy revealed amounts of scopolamine in samples submitted to all treatments, except X-I, in which the amount of this alkaloid was low. High amounts of an unidentified compound (molecular ion m/z 302 and a prominent peak at m/z 129) were noted in extracts from leaves X-I, C1-I and leaves from the nodes immediately above the leaves inoculated with PVX. It is suggested that the synthesis and accumulation of the unidentified compound is a result of stress from mechanical injury and virus inoculation.

Chemical composition, acetylcholinesterase inhibitory and antifungal activities of Pera glabrata (Schott) Baill. (Euphorbiaceae)

Pera glabrata (Schott) Baill. was selected for this study after showing a preliminary positive result in a screening of Atlantic Forest plant species in the search for acetylcholinesterase inhibitors and antifungal compounds. The bioassays were conducted with crude ethanol extract of the leaves using direct bioautography method for acetylcholinesterase and antifungal activities. This extract was partitioned with hexane, chloroform and ethyl acetate solvents. The active chloroform fraction was submitted to silica gel chromatography column affording 12 groups. Caffeine, an alkaloid, which showed detection limits of 0.1 and 1.0 µg for anticholinesterasic and antifungal activities, respectively, was isolated from group nine. After microplate analyses, only groups four, nine, 10, 11 and 12 showed acetylcholinesterase inhibitory activity of 40% or higher. The group 12 was purified by preparative layer chromatography affording four sub-fractions. Two sub-fractions from this group were analyzed by gas chromatography-mass spectrometry and gas chromatography-flame ionization detector. The first sub-fraction showed anticholinesterasic activity and contained two major compounds: 9-hydroxy-4-megastigmen-3-one (84%) and caffeine (6%). The second sub-fraction presented five major compounds identified as 9-hydroxy-4-megastigmen-3-one, isololiolide, (-) loliolide, palmitic acid and lupeol and did not show activity.

Development of instrumentation for amperometric and coulometric detection using ultramicroelectrodes

In this work it is presented the development of a simple, portable and inexpensive instrumentation for amperometric and coulometric detection in different analytical instrumentation systems utilizing ultramicroelectrodes. The software, developed in LabVIEW 7.1TM, is capable to carry out three main detection techniques (amperometric, pulsed amperometric and coulometric detection) and a voltammetric technique (cyclic voltammetry). The instrumentation was successfully evaluated using the following systems: cyclic voltammograms of metallic electrodes in alkaline solutions, flow electrochemical detection of glucose and glycine and direct determination of herbicide glyphosate (electrochemical detection coupled to HPLC).

Determinação espectrométrica dos flavonóides das folhas de Maytenus (Celastraceae) e de Passiflora (Passifloraceae) e comparação com método CLAE-UV

Este trabalho apresenta uma modificação dos procedimentos descritos nas Farmacopéias Francesa e Européia para a análise de flavonoides de Passiflora incarnata L., Passifloraceae, por espectrometria UV-Visível e propõe a sua aplicação na determinação dos flavonoides totais das folhas da espinheira-santa (Maytenus aquifolium Mart. e Maytenus ilicifolia (Schrad.) Planch., Celastraceae) e do maracujá (Passiflora edulis Sims. e Passiflora alata Curtis, Passifloraceae). Os resultados obtidos por espectrometria no UV-Visível foram comparados aos obtidos por cromatografia líquida de alta eficiência (CLAE-UV), encontrando-se resultados estatisticamente similares entre os métodos espectrométrico modificado da Farmacopéia Francesa e CLAE-UV.