Dry-chlorination inductively coupled plasma mass spectrometric method for the determination of platinum group elements in rocks

Abstract

A dry-chlorination procedure has been developed for use in the determination of low concentrations of platinum group elements (PGE) and Au in rock pulps. The PGE and Au, present as native metals, natural alloys and as PGE-(or Au-) bearing sulfide group minerals, are converted by dry-chlorination into PGE (or Au) sodium salts. These salts are dissolved in weak HCl. The solutions are analysed for PGE and Au content by inductively coupled plasma mass spectrometry (ICP-MS). Tests on three reference rock pulps [diluted South African Bureau of Standards Reference Material (SARM)-7 Platinum Ore; diluted INCO S-1800; Nevada Bureau of Mines (NBM) 6a Stillwater] and one gabbro rock showed that the dry-chlorination–ICP-MS method produced results that were usually comparable to, and often better than, fire assay techniques. Reagent contamination was extremely low (Pt⩽1 ng g^–1; other PGE and Au⩽0.2 ng g^–1). The recoveries of PGE obtained by dry-chlorination–ICP-MS were often >90%.