Bioanalytical application of multidimensional open tubular column supercritical fluid chromatography

Summary 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 L 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.