Investigation of matrix effects in boron determination using organic solvents as modifiers for liquid chromatography coupled to ICP-MS

Abstract

The extent and the causes of the reduction in boron signal by organic modifiers typically used in liquid chromatography inductively coupled plasma mass spectrometry (LC-ICP-MS) have been investigated. Three boron containing compounds in three organic solvents were analysed with both ICP-MS and ICP-AES to distinguish between ion effects in the interface to the mass spectrometer and other effects. A large decrease in the boron signal could be seen with all organic solvents used, but the responses of the different boron containing compounds were similar. When compared with elements that have similar mass and ionization energies to boron, the boron signal still decreased more than the signal for other elements. Studies of analyte fractionation in the sample introduction system showed no difference in analyte transport between different elements. A new technique, utilising the introduction of gaseous boron, was developed to distinguish between sample introduction phenomena and plasma or mass spectrometer related effects. The gas introduction experiments showed that the decrease of signal intensity is independent of the sample introduction system and must be caused by a plasma related effect. The decrease was greater in ICP-MS than in ICP-AES, probably because of mass discrimination in the ion optics or vacuum interface caused by polyatomic ions from the solvents.