HYDRIDE GENERATION AS A TOOL FOR DETERMINATION OF CRITICAL ELEMENTS FROM MINE-WASTE BY ICP-MS

Hydride generation (HG) is a novel sample introduction method for determination of several hydride forming elements, including antimony (Sb), arsenic (As), bismuth (Bi), germanium (Ge), lead (Pb) selenium (Se), tellurium (Te) and tin (Sn). HG offers the advantage of multi-element determination when coupled to an ICP-MS instrument. Most notable advantage of HG is its ability for selective determination of target elements from complex samples, such as mine waste, without exposing ICP-MS instrument to elevated levels of unwanted matrix elements. In this work, a multi-element HG approach is developed for determination of As, Bi, Ge, Se, Pb, Sb, Sn and Te by ICP-MS. A quartz dual cyclonic spray chamber equipped with a Teflon nebulizer was used as a gas-liquid separator. Gaseous hydrides were transported to an argon plasma via nebulizer argon gas. An internal standard solution of rhodium was also aspirated via the nebulizer to correct for instrumental sensitivity changes. Hydride generation conditions were examined by reacting 10 µg/L multi-element solution in hydrochloric acid (HCl) and nitric acid (HNO₃) solutions with sodium borohydride (NaBH₄). HCl provided comparatively higher sensitivity for As, Se and Te. Substantial carryover was observed for Sn, Sb and Bi, which was alleviated by mixing the sample solution on-line with 1% (m/v) potassium ferricyanide, K₃Fe(CN)₆, solution prior to reaction with NaBH₄. K₃Fe(CN)₆ also served as an additive that is essential for generation of lead hydride. Optimum HCl concentration was around 1% (v/v) for Ge, Pb and Sn, and 25% (v/v) for As, Se and Te. Bismuth and Sb worked effectively between 0.5 and 30% (v/v) HCl range. A concentration of 2% (m/v) NaBH₄ was found optimum for multi-element hydride generation. Optimum nebulizer (e.g., carrier) argon flow rate was 1 and 1.1 L/min for 1% and 25% (v/v) HCl solutions. Interferences of transition metals, Co, Cr, Cu, Fe, Mn, Ni, V and Zn were not significant at 1 µg/mL level, except for Pb. Copper and Fe inhibited lead hydride generation. Effects were alleviated by increasing K₃Fe(CN)₆ concentration to 2% (m/v). Compared to solution nebulization, sensitivity was enhanced by factor of 100 to 500. The performance of the method will be presented for analysis of Hard Rock Mine Waste (SRM 2780) and bullet lead (C2416) by HG-ICP-MS for As, Bi, Ge, Se, Sb, Sn and Te.