Original HPLC-F method for the simultaneous determination of cocaine and two metabolites in dried blood spots and plasma

Introduction: Cocaine (methyl (1R,2R,3S,5S)-3-(benzoyloxy)-8-methyl-8-azabicyclo[3.2.1]octane-2-carboxylate) is currently the second most widespread illicit drug in Western countries, after Cannabis. In Europe in particular, its use has been increasing in the past few years, following a pattern similar to that of the USA in the 1980s. This severe trend has attracted much attention from governments and health agencies and is creating much concern regarding its negative impact on people’s and in particular on adolescent’s health. It is evident the need for reliable and easily applied analytical methods for the determination of cocaine in abusers. Methods: An original chromatographic method coupled to spectrofluorimetric detection (HPLC-F) is presented herein for the simultaneous determination in dried blood spots (DBS) and plasma of cocaine and two important metabolites, namely benzoylecgonine (its main metabolite) and cocaethylene (the active metabolite formed in the presence of ethanol). Results: The analysis was carried out on a C8 column, using a mobile phase containing phosphate buffer and acetonitrile. Native analyte fluorescence was monitored at 315 nm, while exciting at 230 nm. For DBS, sample pre-treatment was carried out by solvent extraction; for plasma, by solid phase extraction (SPE) with C8 cartridges. Extraction yields (> 91%) and precision values (RSD < 4.8%) were highly satisfactory on both matrices. The method was successfully applied to DBS and plasma samples collected from some cocaine users, both with and without concomitant ethanol intake. Conclusions: The method has demonstrated to be suitable for the monitoring of cocaine/ethanol use by means of DBS and plasma testing. Moreover, it represents a significant improvement over existing ones, since it has the fundamental advantage of allowing the simultaneous quantification of cocaine, benzoylecgonine and cocaethylene, thus making it possible to detect the simultaneous intake of both cocaine and ethanol.