Development and validation of an analytical method for the simultaneous determination of cocaine and its main metabolite, benzoylecgonine, in human hair by gas chromatography/mass spectrometry

Abstract

A new, simple and rapid procedure has been developed and validated for the determination of cocaine and its main metabolite, benzoylecgonine, in human hair samples. After extraction from within the hair matrix by a mixture of methanol/hydrochloric acid (2:1) at 65 degrees C for 3 h, and sample cleanup by mixed-mode solid-phase extraction (SPE), the extracts were analyzed by gas chromatography/mass spectrometry (GC/MS), after derivatization with N-methyl-N-(trimethylsilyl)trifluoroacetamide with 5% chlorotrimethylsilane. Using a sample size of only 20 mg of hair, limits of detection (LODs) and quantitation (LOQs) were, respectively, 20 and 50 pg/mg for cocaine, and 15 and 50 pg/mg for benzoylecgonine, achieving the cut-off values proposed by the Society of Hair Testing for the analysis of these compounds in hair. The method was found to be linear (weighing factor of 1/x) between the LOQ and 20 ng/mg for both compounds, with correlation coefficients ranging from 0.9974 to 0.9996 for cocaine; and from 0.9981 to 0.9994 for benzoylecgonine. Intra- and interday precision and accuracy were in conformity with the criteria normally accepted in bioanalytical method validation. The sample cleanup step presented a mean absolute recovery greater than 90% for both compounds. The developed method may be useful in forensic toxicology laboratories for the analysis of cocaine and benzoylecgonine in hair samples, taking into account its speed (only 3 h are required for the extraction of the analytes from within the matrix, whereas 5 h or even overnight extractions have been reported) and the low limits achieved (using a single quadrupole mass spectrometer, which is available in most laboratories).

Development and validation of a gas chromatography/ion trap-mass spectrometry method for simultaneous quantification of cocaine and its metabolites benzoylecgonine and norcocaine: Application to the study of cocaine metabolism in human primary cultured renal cells

“…As the temperature of incubation for the chosen silylating agent, MSTFA, varies from author to author [30][31][32][33][34], the effectiveness of this derivatization procedure was evaluated using 3 different temperatures: 37, 55, and 80 • C. The main objective was to verify if cocaine chemical stability would be affected by the derivatization temperature. The observed variations were not significant, neither for cocaine, nor for the amount of BE formed along the preparation of the samples, which corresponds to about 2% for all tested temperatures.…”

Head and neck cancer: Response to p53‐based therapeutics

“…The suggested cut‐off concentration is 500 pg/mg for cocaine and 50 pg/mg for its main metabolite, benzoylecgonine (BZE) (Cooper, Kronstrand, & Kintz, 2012). A GC/MS analytical method to quantify cocaine and its main metabolite BZE in hair samples was proposed (Barroso et al, 2008). Despite the simple instrumentation utilized, the method proved to be sensitive and specific, and allowed one to detect 20 and 15 pg/mg of cocaine and BZE, respectively, from only 20 mg of sample.…”

Analysis of Drugs of Abuse in Biological Specimens

“…Barroso et al 51) developed and validated an analytical method for the simultaneous determination of cocaine and its main metabolite, benzoylecgonine, in human hair specimens by GC-MS. After extraction of the hair matrix with a mixture of methanol/HCl (2 : 1) at 65 • C for 3 hr, followed by specimen cleanup by mixed-mode SPE, the extract was analyzed by GC-MS after derivatization with MSTFA with 5% chlorotrimethylsilane. The developed method may be useful for the analysis of cocaine and benzoylecgonine in hair specimens in forensic toxicology laboratories, taking into account the speed and sensitivity achieved with a single quadrupole MS that is available in most laboratories.…”