Simultaneous Determination of As, Sb, Bi and Hg in Geological Samples by HG-Multi-channel-AFS

HG-AFS with 4 channels was applied to the determination of As, Sb, Bi and Hg in geological samples. The sample was dissolved with mixed acid solution of HCl-HNO3-H2O(3+1+4). An aliquot of the sample solution in HCl(1+4) medium was pre-reduced by reacting with thiourea (having its concentration attained to 10 g·L-1 in the solution) for 30 min. Pure argon was used both as carrying gas and shielding gas with their flow-rates at 300 mL·min-1 and 900 mL·min-1 respectively. Intermittent flow mode of sample introduction was adopted in the instrumental operation. Concentration of KBH4 used was 15 g·L-1. Linearities were attained for the 4 elements in definite ranges. Values of detection limits (3S/N) found were (μg·L-1) 0.031 (for As), 0.028 (for Sb), 0.024 (for Bi) and 0.004 8 (for Hg). The proposed method was used for analyzing a geological sample and recovery for the 4 elements was tested by standard addition method, results of recovery found were in the range of 95.4% to 101%.