The GC/MS Determination of Benzoylecgonine in Urine Following an Extractive Alkylation Technique

We describe a GC/MS/COM method for the analytical determination of benzoylecgonine (BE), the primary urinary metabolite of cocaine. A 2-ml urine sample is made basic with NaOH, which contains tetrahexylammonium hydrogen sulfate (THA). The ion pair (BE-THA) Is extracted Into a 5-ml solution of iodoethane in methylene chloride. The 10-minute extraction time results in a 70% conversion of benzoylecgonine to the ethyl ester. Linearity has been demonstrated from 1 to 50 µ g/ml. Quantitation was accomplished by monitoring multiple mass spectral fragments with a precision of 6% (coefficient of variation) or less. The extractive alkylation technique results in a one-step extraction and derivatization that greatly simplifies the overall analysis.