HG-AFS Determination of Arsenic and Antimony in Rocks

AFS with hydride generation was applied to the determination of arsenic and antimony in rocks. Rock sample was crushed to pass sieves with bores of 0.25 mm to 0.42 mm. 0.100 0 to 0.300 0 g of the crushed sample were soaked in 8 mL of an acid mixture of conc. HCl and HNO3 (3+1) for 30 min and then digested in boiling water bath for 2 h. The mixture was transferred to a 50 mL volumetric flask and diluted to mark with water. 5.00 mL of the supernatant were taken and transferred to a 10 mL volumetric flask, 2.5 mL of 100 g·L-1 thiourea-ascorbic acid solution were added and the solution was diluted to 10 mL with HCl (5+95). An aliquot of 1.0 mL was taken for the analysis under prescribed instrumental conditions. 20 g·L-1 KBH4 solution was used as reductant to generate the hydrides of arsenic and antimony. Linear relationships between values of fluorescence intensity and concentrations of As and Sb were obtained in the ranges of 0.50-60 μg·L-1 and 0.50-80 μg·L-1 respectively. The proposed method was used in the analysis of 2 rock CRM′s (GBW 07106 and GBW 07108), contents of As and Sb found were in consistency with the certified values, and values of RSD′s (n=5) found were less than 3.5%.