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The analysis of drugs and their metabolites in biological fluids represents an essential role in pharmaceutical and toxicology studies. High performance liquid chromatography (HPLC) has emerged as a particularly powerful analytical technique for drug analysis since many water soluble compounds are too involatile and/or thermally labile to be analyzed by gas chromatography. [ABSTRACT FROM AUTHOR]

The first report demonstrating the feasibility of supercritical fluids as solvent media for performing enzymatic reactions was published in 1986 (1). Since then several reports have confirmed that the relatively low critical temperature and pressure of supercritical fluid carbon dioxide provides potential for the use of enzymes with thermally labile substrates. These applications, which generally involve the use of immobilized enzymes in feasibility studies for batch scale processes, have been reviewed (2). One study (3) has demonstrated that the stability of nine commercially available enzyme preparations are largely unaffected using supercritical carbon dioxide containing ethanol (3-6%) and water (0.1%), at 35°C, 200 atm for 1 h. On the analytical scale, a few applications have described the use of enzymes in conjunction with supercritical fluid extraction (SFE) for sample preparation of liquid matrices (4). [ABSTRACT FROM AUTHOR]