Simultaneous Determination of Ultra-Trace Pt, Pd, Rh, and Ir in Gold Mining Residue by Inductively Coupled Plasma-Mass Spectrometry (ICP-MS) with an Antimony-Copper Fire Assay and Microwave Digestion

Abstract

The evaluation of the flow direction of platinum group elements (PGEs) during gold-copper ore mining is challenging due to the uneven distribution and low content. Therefore, it is vital to accurately and simultaneously determine ultra-trace PGEs Pt, Pd, Rh, and Ir in gold mining residue samples. In this study, a method to simultaneously determine ultra-trace Pt, Pd, Rh, and Ir in gold mining residue is reported using Sb–Cu fire assay, microwave digestion, and inductively coupled plasma-mass spectrometry (ICP-MS). The Sb–Cu fire assay was used to enrich Pt, Pd, Rh, and Ir, obtaining Sb–Cu alloy particles that concentrate these elements. An optimal microwave method was employed to digest the Sb–Cu alloy particles. In ICP-MS, the collision reaction interface was used to eliminate the interferences of other elements and improve the accuracy. Moreover, the matrix-matched multi-external standards combined with internal standard calibration were utilized to reduce the error. High concentrations of Au, Ag, and Pb showed no interferences with Pt, Pd, Rh, or Ir determination. The limits of detection for Pt, Pd, Rh, and Ir were 0.018, 0.052, 0.064, 0.035 ng·g−1, respectively, and the relative standard deviation was 5.18, 4.66, 1.55, and 3.17%. Additionally, the determination of Pt, Pd, Rh, and Ir in standard reference materials showed good agreement with the certified values. In summary, a reliable and efficient method is provided to determine various PGEs which is of great significance for gold-copper ore mining.