Forensic discrimination of arsenous acid by the analysis of trace impurities wth ICP-AES

Abstract

The application of inductively coupled plasma atomic emission spectrometry (ICP-AES) to the determination of trace impurities in arsenous acid was examined in order to discriminate arsenous acid samples from different origins. About 250 mg of a sample was accurately weighed and put into a glass beaker; 5 ml of HCl and 0.5 ml of HNO3 were then added. The beaker was capped with a watch glass and heated on a hot plate until the sample was completely dissolved. After cooling to room temperature, the sample solution was transferred to a volumetric flask, followed by dilution to 25 ml with purified water. Five elements (Se, Sn, Sb, Pb and Bi) could be determined with RSDs between 0.9% and 5.5% at levels of 120 and 15 μg/g, respectively. The effect of the arsenic matrix and reagents on the background levels and the emission intensities of these elements could be compensated by using standard solutions containing the same amount of acids as the sample solutions, and by adopting a spectroscopic background correction. The obtained values for Sb and Pb were in good agreement with those by the JIS method. The proposed method was applied to 14 kinds of arsenous acid samples from different sources. A comparison of the analytical results made it possible to distinguish 14 samples from each other, except for only 4 pairs. © 2001 The Japan Society for Analytical Chemistry.