MATRIX AND MODIFIER EFFECTS IN THE SUPERCRITICAL-FLUID EXTRACTION OF COCAINE AND BENZOYLECGONINE FROM HUMAN HAIR

The supercritical fluid extraction (SFE) behavior of cocaine and its m ajor metabolite benzoylecgonine (BZE) was investigated and found to be highly dependent upon the chemical nature of the matrix and the manne r in which the target drug analytes are incorporated into or on the ma trix, The recovery of cocaine from Tenon wool, filter paper, drug-fort ified hair, and drug user hair was studied using a variety of CO2/modi fier mixtures, Incorporation of a triethylamine (TEA)/water modifier m ixture provided dramatic improvements in the recovery of cocaine from interactive matrixes, The results suggest that the SF extractability o f cocaine is not limited by analyte solubility; rather, desorption of cocaine from hair binding sites is a rate-limiting step in the SFE pro cess, A displacement SFE mechanism is hypothesized in which TEA (as th e triethylammonium cation) competes with cocaine for negatively charge d hair binding sites, The dependence of extractability on hair/drug bi nding interactions allows the differentiation of cocaine present at di fferent discrete sites in hair based on differences in SFE behavior, T hese findings suggest the potential for distinguishing exogenous (i.e. , environmental) from endogenous (i.e., physiological) sources of drug s in hair. In contrast to the results observed for cocaine, SFE recove ries of BZE were poor from all matrixes and under all conditions studi ed, 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 employ ed.