Desenvolvimento de Métodos Analíticos para Determinação de Cd, Tl e Pb em Subprodutos da Industrialização do Xisto via Espectrometria de Absorção Atômica com Forno de Grafite por Amostragem Direta

Abstract

The purpose of this work was the development of methods for the determination of Cd, Tl and Pb in oil shale by-products by graphite furnace atomic absorption spectrometry with Zeeman-effect background correction using direct analysis. Direct solid sampling was compared to slurry sampling. The pyrolysis and atomization temperatures were 500 ºC and 1700 ºC respectively for Cd using a mixture of 10 μg Pd+ 6 μg in 0.05% (v/v) Triton X-100 as the chemical modifier. The limits of detection (LOD) were 3.4 ng g-1 for solid sampling and 5.5 ng g-1 for slurry sampling. For Tl determination without a chemical modifier, temperatures of pyrolysis and atomization of 900 ºC and 1800 ºC respectively. The LOD obtained for solid and slurry sampling were 11 ng g-1 and 36 ng g-1, respectively. The accuracy of methods was evaluated using standard reference materials NRCC BCSS1 and NIST SRMNIST 2704. The results of DS and SlS were in agreement with certified values for both elements. The method of analysis for determination Pb by SlS was carried. The pyrolysis and atomization temperatures were 900 ºC and 1800 ºC respectively when a mixture of 10 μg Pd + 6 μg in 0.05% (v/v) Triton X-100 was used as the chemical modifier. The LOD were 1.4 μg g-1. In order to compare the results, wet digestion assisted by microwave radiation and using conventional heating were also investigated. The results obtained with direct analysis were in agreement with those obtained by wet digestion assisted by microwave radiation determined by ICP-MS. The results for lead were significantly different with these obtained by wet digestion methods.