Bioanalytical application of multidimensional open tubular column supercritical fluid chromatography

Abstract

On-line multidimensional open tubular column supercritical fluid chromatography (SFC/SFC) using either a flow-switching or a rotary valve-switching interface has been applied to bioanalytical problems. These include the analysis of (a) cholesterol in dried egg yolk, (b) retinoic acids in rat serum, and (c) a digitalis-like factor in peritoneal dialysate from hypertensive patients. A solvent vent injection technique was incorporated in the system, allowing single or multiple volumes of extract (up to 2.0 μL each) to be injected into an uncoated, but deactivated, length of capillary precolumn without flooding of the analytical column. For flow-switching, a well-deactivated, glass-lined offset-cross with a small dead volume was placed between the primary and the secondary column. With a rotary valve-switching interface, a cold trap was employed for refocusing analytes at low pressure from single or multiple fractional cuts after being transferred to the second dimension.