Evaluation of internal standardization for the determination of semivolatile analytes in difficult matrices by simultaneous multielement atomic absorption spectrometry.
The aim of the present work is to investigate the use of the internal standardization technique combined with permanent chemical modification for the determination of two semivolatile analytes, such as As and Se, in difficult matrices by electrothermal atomic absorption spectrometry. Bismuth and tellurium have been evaluated as internal standards to minimize matrix effects on the direct determination of selenium and arsenic in sediments, by simultaneous electrothermal atomic absorption spectrometry using graphite tubes with integrated platform, pre-treated with different masses of Zr and Ir as permanent modifier. A Perkin-Elmer SIMAA 6000 simultaneous multielement spectrometer was used to study the correlation between two integrated absorbance signals. Matrix effects were evaluated by calculating the slope ratio between the analytical curve obtained from reference solutions prepared in 1.0% (v/v) HNO3 and analytical curve obtained from IS additions in matrix solutions. The results showed that Te was the optimal internal standard and 200 μg Zr and 20 μg Ir was the optimal permanent chemical modifier for both analytes. The instrumental limits of detection for As and Se were 1.48 and 1.96 μg L(-1) without the use of an internal standard and 0.59 and 0.35 μg L(-1) when Te was used as an internal standard, respectively. Relative standard deviations for a sample with matrix effect containing 100 μg L(-1) As and 200 μg L(-1) Se were 1.3% and 2.3% (n=20) using 100 μg L(-1) Te, respectively, and for a standard solution sample containing 100 μg L(-1) As and 200 μg L(-1) Se were 3.0% and 1.2% (n=20) using 100μgL(-1) Te, respectively. The accuracy of the proposed method was evaluated by an addition-recovery experiment and by the analysis of different certified reference materials. The recovered values were in the 95-100% range for both analytes.