DEVELOPMENT OF A PRECOLUMN CAPILLARY LIQUID-CHROMATOGRAPHY SWITCHING-SYSTEM FOR COUPLING TO MASS-SPECTROMETRY

A column switching system was developed for capillary liquid chromatog raphy using a robust low back pressure precolumn (PC) for fast loading of large sample volumes. After loading, trapped analytes are transfer red to the capillary separation column by a backflush linear gradient flow. The PC contained a small quantity of reversed-phase C18 material prepared in poly etheretherketone (PEEK) tubing, which is capped at b oth sides by means of high-performance liquid chromatography (HPLC) in -line filters. Gradient backflush elution provided an effective means for preconcentration and refocusing of analytes of different nature an d polarity. The technique showed a clearcut improvement in separation efficiency as compared with switching systems using forward now elutio n of the PC. The system was connected to continuous flow Fast Atom Bom bardment (FAB)/mass spectroscopy for the analysis of steroids and pept ides. Salts and polar compounds present in the sample were removed by extensive washing of the precolumn with an appropriate water percentag e before their elution and separation. The preconcentration of diluted samples on the PC gave an increase in sensitivity of approximately tw o orders of magnitude as compared with wide-bore HPLC-CF (continuous f low) FAB using effluent splitting. (C) 1996 John Wiley & Sons, Inc.