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

The application of inductively coupled plasma atomic emission spectrometry (ICP-AES) to the determination of trace impurities in arsenous acid was exa mined in order to discriminate arsenous acid samples from different origins . About 250 mg of a sample was accurately weighed and put into a glass beak er; 5 mi of HCl and 0.5 ml of HNO3 were then added. The beaker was capped w ith a watch glass and heated on a hot plate until the sample was completely dissolved. After cooling to room temperature, the sample solution was tran sferred 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 mug/g, respectively. The effe ct of the arsenic matrix and reagents on the background levels and the emis sion intensities of these elements could be compensated by using standard s olutions containing the same amount of acids as the sample solutions, and b y adopting a spectroscopic background correction. The obtained values for S b 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 sour ces. A comparison of the analytical results made it possible to distinguish 14 samples from each other, except for only 4 pairs.