Phase-system switching in liquid chromatography/continuous-flow fast-atom bombardment mass spectrometry

A new, attractive application of the phase‐system switching (PSS) technique is demonstrated. The PSS system is used in combination with liquid chromatography coupled to continuous‐flow fast‐atom bombardment mass spectrometry (LC/CF‐FABMS) to achieve flow‐rate reduction from 1.0 mL/min in the high‐performace liquid chromatography (HPLC) system to 15μL/min going into the mass spectrometer. In PSS, a compound of interest, in this case erythromycin 2′‐ethylsuccinate, is enriched after the analytical separation, on a short trapping column, from which it is desorbed subsequently to the LC/MS interface. Optimal mobile phases and flow‐rates can be used for the HPLC separation as well as for the mass spectrometric detection. Desorption of the analyte is achieved either by using a flow‐rate of 15 μL/min without a splitter or a flow‐rate of 230 μL/min with a splitter. Compared to the LC/CF‐FAB MS methods using a conventional bore HPLC column and a splitter, improved detection limits for the model compound were achieved using the PSS method.