Method for quantifying and removing polyatomic interferences on a suite of moderately volatile elements (Zn, Se, Rb, Ag, Cd, In, Sb, Tl, Pb, and Bi) during solution-mode ICP-MS

Abstract

Moderately volatile elements (MVEs: Zn, Se, Rb, Ag, Cd, In, Sb, Tl, Pb, and Bi) have condensation temperatures between 650 and 1250 K. Quantifying the abundances of MVEs in basaltic samples is important for deducing the nature of the source region and, if the samples are old, MVEs could potentially preserve fractionation events occurring at relatively high temperatures during the formation and evolution of the mantle and crust. There are three major issues in quantifying the concentrations of MVEs in basaltic samples: (1) they are present in very low abundances (most <1 μg g⁻¹ or ppb); (2) there is a lack of established standard reference materials (SRMs) for all of the elements investigated here; and (3) several MVEs are plagued with significant polyatomic interferences during mass spectrometric analyses. This study applies solution mode inductively coupled plasma – mass spectrometry (ICP-MS) of whole rock digestions and describes a method to mitigate these issues. Interferences are addressed by analyzing a series of carefully prepared multi-element solutions, which permit the isolation, quantification, and subsequent removal of major polyatomic interferences from their respective MVE ion signals. The lack of SRMs is addressed by applying the method developed here to repeated analyses of basaltic reference materials (RMs) BIR-1 and BHVO-2, so as to begin the task of establishing internationally recognized RMs for these 10 MVEs of interest. The results reported here from 12 analyses each of standards BIR-1 and BHVO-2 demonstrate that this method produces accurate and precise abundances for these MVEs in basaltic samples.