Determination of metal impurity elements in lithium hexafluorophosphate using inductively coupled plasma tandem mass spectrometry based on reaction gas mixtures

Abstract

An analytical method was developed for inductively coupled plasma tandem mass spectrometry (ICP-MS/MS) based on reaction gas mixtures to eliminate the spectral interferences. Lithium hexafluorophosphate (LiPF6) was dissolved in ultrapure water, and the presence of 18 metal impurity elements were determined directly by ICP-MS/MS. In the MS/MS mode, the interference of argide ions could be quickly eliminated by adding H2 to the reaction gas O2, while the addition of H2 to the reaction gas NH3/He promoted the formation of -NH3 from the adducts -NH and -NH2. The reaction gas mixtures O2/H2 and NH3/He/H2 were used to eliminate the interferences when using the mass shift method and on-mass method. The internal standard ions with similar mass numbers and similar mass spectrometry behaviors were selected to correct for instrument instability, signal drift, and matrix effects. The accuracy of the method was evaluated by comparative analysis using sector field inductively coupled plasma mass spectrometry (SF-ICP-MS). The results show that the interference can be completely eliminated by using mixtures of reaction gases mixtures, while achieving high sensitivities for the analytes. The limits of detection (LODs) ranged from 0.30 to 63.8 ng L−1. At 95% confidence level, no significant difference was observed between the results obtained from ICP-MS/MS and SF-ICP-MS analyses, and the relative standard deviation (RSD) was ≤5.67%. The developed method provides simple sample processing, good accuracy, and high precision, and it can be used for the interference-free determination of metal impurity elements in LiPF6.