Estudo da utilização de padrão interno em determinações multielementares por espectrometria de absorção atômica com atomização eletrotérmica e detecção simultânea / Study of the use of internal standard for multielement determinations by electrothermal atomic absorption spectrometry with simultaneous detection

AUTOR(ES)

Paulo Rogério Miranda Correia

DATA DE PUBLICAÇÃO

2004

RESUMO

A systematic study involving the use of internal standard for multielement determinations by electrothermal atomic absorption spectrometry was developed. The main objective of this work was evaluate the possibility of improving precision and accuracy of the analytical results for biological fluids. The sample pre-treatment was reduced to a single dilution step with surfactant (Triton X-100) and acid (HNO3), increasing the amount of concomitant introduced into the atomizer. The preliminary selection of the elements to be tested as internal standard considered the resemblance of physico-chemical parameters related with the atomization process. Thus, Ag, Bi, In and Tl were tested as internal standard for the simultaneous determination of Cd/Pb in blood and urine, and Bi, Ge, In, Sb, Sn and Te were the selected elements for the determination of Mn/Ni/Se in blood serum. The correction of the results obtained for the simultaneous determination of Cd and Pb in blood was achieved when Ag was used as internal standard, in presence of NH4H2PO4 as chemical modifier. An improvement for the accuracy of the results was observed for both analytes after their correction with the internal standard. On the other hand, the results obtained for the urine analysis were not corrected by using the tested elements. The best results for the simultaneous determination of Mn, Ni and Se were observed when Bi, Sn and Te were used as internal standard. However, the correction for the results for all analytes was not possible by using only one internal standard. The best performance in presence of the serum was obtained for Bi, which improves slightly the precision for the Se results. Thus, the internal standardization for the simultaneous determination of Mn, Ni and Se was not efficient. The internal standardization in ETAAS, aiming the improvement of precision and accuracy of the analytical results, is a strategy as complex as the interference effects to be corrected: more studies are required in order to better understand how the adoption of a compromised condition disturbs the atomization processes, as well as to get more information about the physical and chemical interference caused by complex samples, analyzed by ETAAS after a single dilution step. The chemical modifier and the selected temperatures for the pyrolysis and atomization steps are critical parameters for the performace of an internal standard and they should be carefully considered.

ASSUNTO(S)

forno de grafite fuidos biológicos multielement determination padronização interna simultaneous detection atomic absorption spectrometry chumbo electrothermal atomization trace-element analysis graphite furnace análise de elementos-traço manganês sangue determinação multielementar lead nickel selenium soro sangüíneo urina cadmium blood selênio detecção simultânea níquel biological fluids atomização eletrotérmica cádmio manganese serum urine espectrometria de absorção atômica internal standardization

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