Simultaneous Determination of Selenium and Tellurium in Tungsten Ore by Hydride Generation Atomic Fluorescence Spectrometry

After sieving and drying, about 0.2 g of sample was taken and dissolved by methods of high temperature-atmospheric pressure digestion or microwave digestion. The sample was digested at 120 ℃ for 3 h in a covered 100 mL-teflon beaker with 10 mL of nitric acid, 5 mL of hydrofluoric acid and 1 mL of perchloric acid, and continuously heated at 200 ℃ until perchloric acid smoked for about 3 min. After cooling to room temperature and rinsing walls of the beaker, the mixture was heated until perchloric acid smoked, and the high temperature-atmospheric digestion solution was obtained. The sample was put into a digestion tank, wetted with a small amount of water, and digested with 2 mL of nitric acid, 2 mL of hydrofluoric acid and 1 mL of perchloric acid under temperature-programmed condition. After cooling to room temperature, the solution was transferred into a 30 mL-teflon beaker, and heated at 200 ℃ until perchloric acid smoked for about 3 min. After cooling and rinsing walls of the beaker, the mixture was heated continuously until perchloric acid smoked, and the microwave digestion solution was obtained. The above solution was mixed with 10 mL of 4.0 mol·L^-1 hydrochloric acid solution, and the mixed solution was heated at 80 ℃ for 30 min. After cooling, 10 mL of 10 g·L^-1 (calculated by iron) ferric chloride solution was added, to effectively mask the interference of coexisting ions including W³⁺, Cu²⁺, Zn²⁺ and Bi³⁺, and the mixed solution was diluted to 50 mL with 4.0 mol·L^-1 hydrochloric acid solution. After settling until clear, an appropriate amount of supernatant was taken, introduced into the hydride generation atomic fluorescence spectrometer with 4.0 mol·L^-1 hydrochloric acid solution as carrier liquid and 20 g·L^-1 sodium botohydride solution as reducing agent, and detected at 400 mL·min^-1 carrier gas flow. It was shown that linear relationships between values of the mass concentration and corresponding fluorescence intensity of selenium and tellurium were kept in the range of 0.10-20.00 μg·L^-1, with detection limits (3s) of 0.008, 0.006 μg·L^-1, respectively. The standard substances (GBW 07240, GBW 07241 and GBW 07284) were determined 5 times in parallel, and the determined values of selenium and tellurium obtained by methods of high temperature-atmospheric pressure digestion and microwave digestion were within the uncertainty ranges of the certified values, with RSDs (n=5) of the determined values less than 4.0%. The proposed method was applied to the analysis of actual tungsten ore samples, and the determined values of the high temperature-atmospheric pressure digestion method were basically consistent with those of the microwave digestion method.