ICP-MS Analysis of Noble Metals at Low Levels in Geological Reference Materials and Ores

• Published in: Spectroscopy (Springfield, Or.) Or.), 2018-09, Vol.33 (s9), p.16-34
• Main Authors: Kutscher, Daniel, Leykin, Alexey, Nelms, Simon, Ducos, Shona McSheehy
• Format: Magazinearticle
• Language: English
• Subjects: Calibration; Detection; Geology; Gold; Hafnium; Heavy metals; Hydrochloric acid; Impact analysis; Inductively coupled plasma mass spectrometry; Interference; Iridium; Kinetic energy; Mass spectrometry; Mass spectroscopy; Metals; Mineral deposits; Minerals; Mining; Noble metals; Ores; Platinum; Quadrupoles; Reference materials; Rhodium; Scientific imaging; Tantalum; Trace metals
• ISSN: 0887-6703; 1939-1900

In most cases, elements such as gold, platinum, rhodium, and iridium, generally considered noble metals and partly belonging to the so-called platinum group metals (PGMs), are considered interference free in inductively coupled plasma-mass spectrometry (ICP-MS). However, in cases where they need to be accurately quantified at low levels, for example, to determine if their concentration in an ore deposits is high enough to economically justify mining and processing the ore, other elements may easily interfere and cause significant bias. Even trace amounts of hafnium and tantalum severely affect the detection of Pt and Au as a result of interference from HfO, HfOH, and TaO, and negatively impact analysis results. Especially when very low amounts need to be detected, kinetic energy discrimination (KED), the primary tool applied to remove polyatomic interferences in single-quadrupole ICP-MS, is not sufficiently effective to eliminate all interferences at the level required for the accurate quantification of ultratrace amounts of Au, Pt, Rh, and Ir.