The supercritical fluid extraction (SFE) behavior of cocaine and its major metabolite benzoylecgonine (BZE) was investigated and found to be highly dependent upon the chemical nature of the matrix and the manner in which the target drug analytes are incorporated into or on the matrix. The recovery of cocaine from Teflon wool, filter paper, drug-fortified hair, and drug user hair was studied using a variety of CO2/modifier mixtures. Incorporation of a triethylamine (TEA)/water modifier mixture provided dramatic improvements in the recovery of cocaine from interactive matrixes. The results suggest that the SF extractability of cocaine is not limited by analyte solubility; rather, desorption of cocaine from hair binding sites is a rate-limiting step in the SFE process. A displacement SFE mechanism is hypothesized in which TEA (as the triethylammonium cation) competes with cocaine for negatively charged hair binding sites. The dependence of extractability on hair/drug binding interactions allows the differentiation of cocaine present at different discrete sites in hair based on differences in SFE behavior. These findings suggest the potential for distinguishing exogenous (i.e., environmental) from endogenous (i.e., physiological) sources of drugs in hair. In contrast to the results observed for cocaine, SFE recoveries of BZE were poor from all matrixes and under all conditions studied. Its increased polarity, the presence of an additional binding site, and the possibility of multiple charged states suggest that poor BZE recoveries may be due to both poor analyte solubility and failure to desorb the analyte from hair binding sites under the conditions employed.

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Supercritical fluid extractions (SFEs) of 21 polychlorinated biphenyls (PCBs) and 8 organochlorine pesticides (OCPs) from freeze-dried mussel tissue are compared with traditional Soxhlet extractions. The aim was to determine the efficacy of supercritical CO2 to extract these 2 classes of lipophilic compounds. A spike study to determine the feasibility of on-line cleanup by inclusion of an inert matrix (activated alumina) in the extraction vessel showed that the chemical integrity of the PCBs was not compromised, whereas some DDTs were decomposed to their respective metabolites. Relatively long static extraction time, higher density, and lower temperature yielded quantitative recoveries of PCBs from freeze-dried mussel tissue with good reproducibilities. Recoveries of OCPs were nonquantitative and highly variable. Finally, the efficacy of fluoroform (CHF3) as an alternative supercritical fluid to selectively extract PCBs and OCPs was studied. Fluoroform yielded nonquantitative and variable recoveries of PCBs and OCPs, but its use eliminated the need for in situ alumina to retain coextracted lipids from the matrix.