ICP-MS Determination of Platinum Metals in Black Shale Enriched by Tin Fire Assay

Platinum metals in black shale were enriched by the method of tin fire assay. The precious metal precipitate obtained was dissolved in mixed acid of HCl-HNO3 (3+1), and contents of platinum metals in the solution were determined by ICP-MS. Lutetium was used as internal standard; and a mixture of light MgO and high purity SiC (2+1) was used as covering reagent to avoid the volatilization of Os and Ru. Linear relationships between values of spectral intensity and mass concentration of the platinum metals were kept in definite ranges. Detection limits (3σ) found were in the range of 0.018-0.20 ng·g-1. Tests for recovery were made by standard addition method, giving values of recovery in the range of 80.0%-110% with RSD′s (n=11) in the range of 5.9%-14%.