Removal of spectral interferences on noble metal elements using MS/MS reaction cell mode of a triple quadrupole ICP-MS

Abstract

The trace level analysis of the eight noble metal elements by inductively coupled plasma mass spectrometry (ICP-MS) is hindered by the formation of polyatomic ion interferences; those elements are ruthenium (Ru), rhodium (Rh), palladium (Pd), silver (Ag), osmium (Os), iridium (Ir), platinum (Pt) and gold (Au). The resolution capabilities of sector field ICP-MS is insufficient to resolve some of the interferences. A new strategy using a triple quadrupole ICP-MS (ICP-QQQ) with highly reactive ammonia gas (NH₃) is presented. The tandem MS configuration of the instrument allows unprecedented control over the ions that enter the collision reaction cell, and therefore ensures consistent reaction processes in the cell, even when the sample composition is complex and variable. Eight noble metal elements spiked at the 1 ng g⁻¹ level in a complex solution containing Cu, Zn, Ni, Mo, Y, Sr, Rb, Zr, Nb, Pb, Hg (1 μg g⁻¹), Ta, W, Hf and REEs at 10 μg g⁻¹ were accurately quantified by removing the spectral interferences with the NH₃ reaction cell of the ICP-QQQ.