QUANTITATIVE OPEN-TUBULAR SUPERCRITICAL FLUID CHROMATOGRAPHY USING DIRECT INJECTION ONTO A RETENTION GAP

摘要

Injection in open-tubular supercritical fluid chromatography is usually accomplished using a dynamic-flow-splitting or time-splitting technique. These techniques limit the effective injection volumes to low-nanoliter levels. Sample volumes can be increased significantly without broadening the detected peaks, and injection precision improved by using direct injection and a retention gap. The required instrument modifications are simple and very inexpensive. The initial oven temperature and pressure must be set with respect to the phase behavior of the binary mixture formed by the mobile phase and the sample solvent. Relative standard deviations of peak areas and peak heights (comparing the same peak among repeated injections) are in the range of 0.6-1.8% for well-behaved solutes using injection volumes of 0.1 and 0.5 mu L.