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This paper reports the development of a method of simultaneous determination of iron and nickel in fluoropolymers by high-resolution continuum source graphite furnace atomic absorption spectrometry (HR-CS GF AAS) with direct solid sampling. In order to carry out simultaneous measurements, both the main resonance line of nickel (232.003nm) and the adjacent secondary line of iron (232.036nm) were monitored in the same spectral window. The proposed method was optimized with a perfluoroalkoxy (PFA) sample and was applied to the determination of iron and nickel in fluorinated ethylene propylene (FEP) and modified polytetrafluoroethylene (PTFE-TFM) samples. Pyrolysis and atomization temperatures, as well as the use of Pd and H2 (during pyrolysis) as chemical modifiers, were carefully investigated. Compromise temperatures for pyrolysis and atomization of both analytes were achieved at 800 and 2300°C, respectively, using only 0.5Lmin(-1) H2 as chemical modifier during pyrolysis. Calibration curves were performed with aqueous standards by using a single solution which contained both analytes. Limits of detection were 221 and 9.6ngg(-1) for iron and nickel, respectively. Analyte concentrations in all samples ranged from 3.53 to 12.4µgg(-1) for iron and from 37 to 78ngg(-1) for nickel, with relative standard deviation less than 19%. Accuracy was evaluated by comparing these results with those obtained by inductively coupled plasma mass spectrometry after sample digestion by microwave-induced combustion and no significant statistical difference was observed.

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The effect of phenyl selenoacetylene and its selenoxide on d-aminolevulinate dehydratase from liver of adult rats (mammalian source) and from cucumber leaves (plant source) was investigated. In vivo, selenides can be oxidized to selenoxides by flavin-containing monooxygenases and selenoxides can regenerate selenides by thiol oxidation. The compound phenyl selenoacetylene was converted to selenoxides by reaction with hydrogen peroxide. Phenyl selenoacetylene inhibited mammalian and plant d-aminolevulinate dehydratase with an IC 50 about 250 mM and Ͼ400 mM, respectively. Its selenoxide inhibited the enzyme more strongly, with IC 50 values of 45 mM and 100 mM for the mammalian and plant source, respectively. The selenoxide inhibitory action was antagonized by dithiothreitol suggesting the involvement of -SH groups. Moreover, d-aminolevulinate dehydratase from a plant source was inhibited by the selenoxide, suggesting a possible involvement of -SH groups located at a site distinct from the region implicated in Zn 2π binding in mammalian daminolevulinate dehydratase. The results of the present study suggest that (i) d-aminolevulinate dehydratase is a potential molecular target for phenyl selenoacetylene, due to the oxidation of enzyme sulfhydryl groups, and that (ii) the monooxygenation of this selenocompound, which in vivo could be possibly mediated by flavin-containing monooxigenases, increases its inhibitory effect.d-Aminolevulinate dehydratase is an essential enzyme in most organisms as a component of the haem biosynthetic pathway, catalyzing the condensation of two molecules of d-aminolevulinic acid to form the monopyrrole porphobilinogen (Sassa 1998). d-Aminolevulinate dehydratase is a sulfhydryl-containing enzyme and its activity is highly sensitive to the presence of elements that oxidize -SH groups like mercury lead, organic selenium and tellurium compounds

Um método para determinação de arsênio em BaSO 4 por espectrometria de absorção atômica com aquecimento eletrotérmico e introdução de amostras sólidas (SoS-ET AAS) é descrito. Foram avaliados dois sistemas de correção de fundo (BG), deutério e efeito Zeeman (Z). Com o uso combinado de hidrogênio e Pd o BG foi diminuído. Resultados exatos e precisos foram obtidos usando Z-SoS-ET AAS. O desvio padrão relativo usando Z-SoS-ET AAS foi menor que 9,5%. O limite de detecção foi 0,005 mg g -1 e a massa característica foi 25,4 pg. Os resultados foram comparados com os obtidos usando o método de preparo de amostras sugerido pela Farmacopeia Europeia, com determinação usando espectrometria de emissão ótica e espectrometria de massas, ambos com plasma indutivamente acoplado, porém os resultados foram cerca de 20% menores. Vantagens como simplicidade, elevada frequência de determinações e boa exatidão foram obtidos em comparação com o método descrito na farmacopeia.A method for arsenic determination in pharmaceutical grade BaSO 4 by solid sampling electrothermal atomic absorption spectrometry (SoS-ET AAS) is described. Two background (BG) correction systems, deuterium and Zeeman-effect (Z), were evaluated. Background was decreased by using hydrogen combined with Pd. Accurate and precise results were obtained using Z-SoS-ET AAS. Relative standard deviation using Z-SoS-ET AAS was lower than 9.5%. Limit of detection was 0.005 mg g -1 and characteristic mass was 25.4 pg. Results were also compared with those obtained using the preparation method suggested by European Pharmacopoeia for BaSO 4 followed by determination using inductively coupled plasma optical emission spectrometry and inductively coupled plasma mass spectrometry. Results were around 20% lower than results obtained using the proposed method. Some advantages as simplicity, higher sample throughput were found when compared with the official method currently described in pharmacopoeia.

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