The interference standard method: evidence of principle, potentialities and limitations

Abstract

The interference standard (IFS) method is a calibration approach recently proposed to overcome polyatomic interference in quadrupole-based inductively coupled mass spectrometry (ICP-QMS). Based on the hypothesis that interfering ions and IFS species such as ³⁶Ar⁺, ³⁶ArH⁺ and ³⁸Ar⁺ present similar behaviors in the plasma, the IFS method has successfully been applied in several analytical procedures. In this work, analytes, interfering ions and IFS species are monitored by high-resolution double focused sector field inductively coupled plasma mass spectrometry (HR-SF-ICP-MS) to achieve a better understanding of the mechanism of the IFS method. The relationship between accuracy and signal variations for interfering and IFS species is explored. Critical cases of polyatomic interference in elemental determination using quadrupole-based ICP-MS instruments, such as the ones observed for ³⁹K⁺, ⁷⁵As⁺, ²⁸Si⁺ and ³²S⁺, are evaluated. The limitations of the IFS method and the conditions under which it can be most effective are discussed. This is a simple and efficient method that could be extended to other analytical techniques provided that interfering and IFS species present similar signal behaviors.