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 experiments were conducted with mobile phase of pure CO2 and methanol-modified CO2 under flow injection and chromatographic conditions. The effects of various operational parameters were characterized. The electron impact limits of detection (LODs) of the system for single ion monitoring and scan modes were determined to be 5 and 40 ng for caffeine, respectively. These LODs are 2.5 to 25 times better than previous reported estimates. Sensitivity was found to be highly dependent on the modifier percentage with 4% methanol-modified CO2 yielding optimal results. Separations of phenylurea pesticides and steroids are shown as demonstrations of system utility. Background subtracted electron impact spectra were artifact-free and comparable with on-line library spectra.