Ultra-trace determination of vanadium in lake sediments: a performance comparison using O2, N2O, and NH3 as reaction gases in ICP-DRC-MS

Abstract

A study was conducted to develop an accurate method for the determination of vanadium in environmental samples by inductively coupled plasma mass spectrometry (ICP-MS), coupled with a dynamic reaction cell (DRC), using two different chemical resolution strategies: (a) direct removal of interfering ClO⁺ and (b) vanadium oxidation to VO⁺. The performance of three reaction gases that are suitable for handling vanadium interference in the dynamic reaction cell was systematically studied and evaluated: ammonia for ClO⁺ removal and oxygen and nitrous oxide for oxidation. Although it was able to produce comparable results for vanadium to those using oxygen and nitrous oxide, NH₃ did not completely eliminate a matrix effect, caused by the presence of chloride, and required large scale dilutions (and a concomitant increase in variance) when the sample and/or the digestion medium contained large amounts of chloride. Among the three candidate reaction gases at their optimized conditions, creation of VO⁺ with oxygen gas delivered the best analyte sensitivity and the lowest detection limit. Vanadium results obtained from fourteen lake sediment samples and a certified reference material (CRM031-040), using two different analyte/interference separation strategies, suggested that the vanadium mono-oxidation has advantages over the conventional method using NH₃ for ultra-trace vanadium determination by ICP-DRC-MS and can be readily employed in relevant environmental chemistry applications.