Although gas chromatography/mass spectrometry (GC/MS) is the most powerful technique for analysing cocaine and its hydrolysis products (benzoylecgonine, ecgonine methyl ester and ecgonine) in urine, the sample pretreatment required is rather laborious and involves a large number of steps. This paper reports a continuous method for the separation (based on the retention properties of cocaine and its major metabolites on a reversed phase C18 column), preconcentration (evaporation under nitrogen) and derivatization (collection of the residue in a few microlitres of derivatizing reagent) of cocaine and its metabolites in urine samples for subsequent analysis by GC/MS. Calibration graphs are linear from 5 to 3000 ng/mL; the detection limits are 1 ng/mL (cocaine and ecgonine methyl ester), 20 ng/mL (benzoylecgonine) and 200 ng/mL (ecgonine). The method was applied to illicit cocaine samples and to urine from a drug addict.
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Cárdenas et al. (1996) studied this question.