PACKED-COLUMN SUPERCRITICAL-FLUID CHROMATOGRAPHY COUPLED WITH ELECTROSPRAY-IONIZATION MASS-SPECTROMETRY

A new approach to combined supercritical fluid chromatography-mass spe ctrometry (SFC-MS) was explored using a two-pump supercritical fluid c hromatograph, and a packed column with the outlet directly interfaced to an electrospray (ES) ion source attached to a single quadrupole mas s spectrometer. The experimental set-up is described and preliminary r esults are reported for mobile phase flow-rates in the range 0.15-1 ml /min, using CO2 modified by the addition of 1-30% (v/v) of a polar org anic solvent. The combined system has a greater potential for the anal ysis of polar molecules by MS than earlier SFC-MS instruments that uti lized capillary column SFC directly coupled to the ion source of a che mical ionization mass spectrometer. A liquid-phase ionization process was utilized for solute ion formation, and it could be applied to the determination of high-mass and polar molecules separated by packed col umn SFC; however, the MS response is dependent on the mobile phase com position and the SFC-ES-MS instrument is still limited to the determin ation of low-mass samples owing to cold trapping on some critical surf aces.