EVALUATION OF THE PARTICLE-BEAM INTERFACE FOR PACKED-COLUMN SUPERCRITICAL-FLUID CHROMATOGRAPHY MASS-SPECTROMETRY WITH PURE AND MODIFIED CO2

The particle beam interface was evaluated for microbore packed-column supercritical fluid chromatography-mass spectrometry coupling. The exp eriments were conducted with mobile phase of pure CO2 and methanol-mod ified CO2 under flow injection and chromatographic conditions. The eff ects of various operational parameters were characterized. The electro n impact limits of detection (LODs) of the system for single ion monit oring and scan modes were determined to be 5 and 40 ng for caffeine, r espectively. These LODs are 2.5 to 25 times better than previous repor ted estimates. Sensitivity was found to be highly dependent on the mod ifier percentage with 4% methanol-modified CO2 yielding optimal result s. Separations of phenylurea pesticides and steroids are shown as demo nstrations of system utility. Background subtracted electron impact sp ectra were artifact-free and comparable with on-line library spectra.