Confirmation of cocaine exposure by gas chromatography-mass spectrometry of urine extracts after methylation of benzoylecgonine.
Volatility and thermal stability are necessary physical-chemical properties for analysing a substance by gas chromatography. A derivatization step is required before gas chromatography of benzoylecgonine (the main metabolite of cocaine). In the literature, reactions such as silylation, perfluoroalkylation or alkylation are the most frequently used to derivatize benzoylecgonine. However, they allow the formation of products sensitive to moisture or require a purification step. So, a procedure to derivatize benzoylecgonine with diazomethane before gas chromatographic analysis was evaluated. A study was performed to evaluate the efficiency of conversion of benzoylecgonine in cocaine, the necessary time for reaction and the stability of ethereal solution of diazomethane. The reaction was shown to be very fast in mild conditions and there was no need for a further purification step. When benzoylecgonine was extracted from urine by solid-phase extraction and derivatized with diazomethane, concentrations as low as 25 ng/ml could be detected using GC-MS in the full scan mode.
Yonamine
Maurício
M
College of Pharmaceutical Sciences, Toxicology, University of São Paulo, USP Av. Professor Lineu Prestes, 580 CEP 05508-900, São Paulo, SP, Brazil. yonamine@usp.br
Silva
Ovandir Alves
OA
D003042:Cocaine / Q000031:analogs & derivatives* / Q000652:urine*; D008401:Gas Chromatography-Mass Spectrometry / Q000379:methods*; D008745:Methylation; D012015:Reference Standards; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity
C005618:benzoylecgonine; D003042:Cocaine