Interference standard: a new approach to minimizing spectral interferences in inductively coupled plasma mass spectrometry

Abstract

Spectral interferences are the most critical issue in inductively coupled plasma mass spectrometry determinations. The effects of isobaric polyatomic ions on accuracy often represent an important limitation to the application of this technique to more complex matrices. This aspect is especially critical in quadrupole-based instruments and the most common approaches to minimizing the problem are based on collision-reaction cells and interfaces. In this work a new strategy based on minimizing the interfering ion signal variation is used to improve accuracy in K, As, P and Si determinations. Different from traditional internal standard methods, argon species naturally present in the plasma are used as probes to correct fluctuations in the interfering ion rather than in the analyte signal. Accuracy is significantly improved with no instrumental modification or post-plasma reactions. At the best conditions, recoveries ranging from 86 to 107% were obtained for all elements evaluated in different certified reference materials and spiking studies. Results were comparable and sometimes better than recoveries obtained with a collision–reaction interface. Adequate precision, accuracy and sensitivity were obtained while using the ³⁸Ar⁺ probe even for isotopes prone to severe isobaric interferences such as ²⁸Si.