Enhanced Detection of Sulphur and Phospho-rous Containing Compounds in HPLC-Induc-tively Coupled Plasma Mass Spectrometry Using Chemical Resolution via Hexapole-Based Reaction with Oxygen

Abstract

The sensitive detection of sulphur and phosphorous-containing compounds using HPLC-ICPMS is difficult due to the high background caused by polyatomic interferences. One potential solution to the problem of polyatomic interferences for S and P is to react the latter with oxygen in the collision hexapole to separate them from interferences eg; (O₂ on S and NOH on P). This has the effect of moving the detection mass from 31 and 32 to 47 and 48 m/z for P and S respectively. This region is clear from interferences thereby providing an increase in the sensitivity of detection for the analytes of approximately 50–100 fold. For omeprazole, a model S containing compound, a limit of detection (LOD) of 800 pg on column was achieved, an increase of ca. 100 fold in sensitivity. Similarly in the case of ZD6126 a phosphorous-containing pro-drug, an increase in sensitivity of 50 times was observed with an LOD of 1 ng on column.