A dynamic reaction cell (DRC) solution to oxide-based interferences in inductively coupled plasma mass spectrometry (ICP-MS) analysis of the noble metals

Noble metals are subject to a number of significant oxide-based interferenc es in ICP-MS analysis. Quantification of these interferences has been large ly overlooked despite evidence which suggests that they may, in some cases, represent a significant source of analytical error. Their removal would th erefore constitute a significant improvement in analytical accuracy. In thi s study the oxides that interfere with noble metal analysis have been quant ified relative to CeO+/Ce+ ratios. A dynamic reaction cell (DRC) based solu tion to the problem is introduced, which works in complete contrast to conv entional ICP-MS analysis where the formation of oxides is undesirable and o perating conditions are optimised to limit their production. Oxygen reactio n gas is utilised actively to promote oxidation of interfering species to h igher oxides, with a resulting separation of analyte from interfering oxide . Results are presented for Hf, Ta, Nb, and Zr where the single oxide inter feres with a noble metal analyte mass. Various higher oxides are formed, le aving the mass free from interference. The reaction mechanism has been dete rmined in each case by monitoring of new multiple-oxide species and scans o f the entire mass range to identify new product species. Results confirm th e success of an in-cell separation of analyte from metal oxide, facilitatin g improved detection limits and isotope-ratio precision. The suitability of this method for general environmental use is demonstrated by analysis of a certified soil reference material and isotope-ratio analyses.