COUPLING OF ION-PAIR LIQUID-CHROMATOGRAPHY AND THERMOSPRAY MASS-SPECTROMETRY VIA PHASE-SYSTEM SWITCHING WITH A POLYMERIC TRAPPING COLUMN

A trapping column packed with polymeric material (PLRP-S) was used to couple ion-pair liquid chromatography on-line with thermospray mass sp ectrometry by phase-system switching. Phase-system switching was used to remove non-volatiles from the eluent before it entered the mass spe ctrometer. The total analytical system was optimized for chlorinated p henoxy acids, which were separated as ion pairs with cetyltrimethylamm onium bromide as ion-pair reagent. Parameters such as percentage of mo difier and concentrations of ion-pairing reagent and buffer affected t he sorption of the ion-pair on the trapping column. Desorption was eff ected by protonation of the acids with, e.g., trifluoroacetic acid or an ion-pair switch with, e.g., ammonium formate. The influence of pH a nd modifier concentration during desorption was examined. In addition to target-compound analysis, group-selective analysis was also demonst rated. As an example, the system was used to identify chlorinated phen oxy acids in river Rhine water.