Simultaneous detection in urine of cocaine and its main metabolites

The simultaneous detection in urine of cocaine (CO), and the main biotransformation products, benzoylecgonine (BE) and ecgonine methyl ester (EME), is difficult due to their different physicochemical properties. The method presented involves a bonded silica solid-phase extraction procedure that allows mixed ionic and apolar interactions with the analyte. After extraction the compounds are derivatized sequentially with ethyliodide to obtain the BE ethyl ester derivative, and with N-methyl-N-trimethylsilyl trifluoroacetamide (MSTFA) to obtain the O-TMS derivatives. The derivatized compounds are then analysed by a capillary (methylphenylsilicone) gas chromatographic system equipped with a specific nitrogen-phosphorus detector. The method is suitable for the confirmation and quantitation of CO and its main metabolites in urine. BE levels in urine samples (n = 20) measured by the described method and by an immunological technique were in close agreement (r = 0.999).