Simultaneous Determination of 11 Metal Elements in Bauxite by Microwave Digestion-ICP-MS

A method for simultaneous determination of 11 metal elements (Li, Cr, Cu, Fe, Ti, K, Na, Ca, Mg, Pb and Zn) in bauxite was established by microwave digestion-ICP-MS. After crushing, grinding and drying of bauxite sample, 0.1 g of sample was taken and mixed with 3 mL of sulfuric acid, 1 mL of nitric acid, 2 mL of hydrofluoric acid and 3 mL of hydrochloric acid, and the mixture was digested by microwave according to the temperature program; then 10 mL of 40 g·L^-1 boric acid solution was added and kept on digesting at 120℃ for 10 min, to make the digestion solution clear. The sample solution was taken out after cooling, heated to nearly dryness at 180℃, diluted with 1% (volume fraction) nitric acid solution, and determined by ICP-MS. The matrix interference was eliminated by using the series of matrix matching mixed standard solution prepared with 10 g·L^-1 aluminum matrix solution and adding Sc, Ge and Bi as internal standard elements, and the overlapping interference of spectral lines was eliminated by selecting the appropriate isotope. The results showed that linearity relationships between mass concentrations and the response value ratios of 11 elements to internal standard elements were kept in the definite ranges, with detection limits (3s) in the range of 0.011-1.400 mg·kg^-1. The spiked recovery test was made on the actual samples, the determined values were found in the range of 0.13-72.21 mg·L^-1, RSDs (n=6) of the determined values was in the range of 0.69%-2.6%, and values of recovery was in the range of 94.0%-106%. The proposed method was used to analyze 3 bauxite composition analysis reference materials, including GBW 07177, GBW 07179 and GBW 07180, giving the determined values within the range of certified values.