Coupling of ion-pair liquid chromatography and thermospray mass spectrometry via phase-system switching with a polymeric trapping column

Abstract A trapping column packed with polymeric material (PLRP-S) was used to couple ion-pair liquid chromatography on-line with thermospray mass spectrometry by phase-system switching. Phase-system switching was used to remove non-volatiles from the eluent before it entered the mass spectrometer. The total analytical system was optimized for chlorinated phenoxy acids, which were separated as ion pairs with cetyltrimethylammonium bromide as ion-pair reagent. Parameters such as percentage of modifier and concentrations of ion-pairing reagent and buffer affected the sorption of the ion-pair on the trapping column. Desorption was effected by protonation of the acids with, e.g. , trifluoroacetic acid or an ion-pair switch with, e.g. , ammonium formate. The influence of pH and modifier concentration during desorption was examined. In addition to target-compound analysis, group-selective analysis was also demonstrated. As an example, the system was used to identify chlorinated phenoxy acids in river Rhine water.