Quantitative analysis of cocaine in human hair by HPLC with fluorescence detection

Cocaine is currently one of the most widespread abuse drugs in the world. Since hair cocaine concentrations are a reliable marker of exposition to the drug, an original liquid chromatographic method has been developed for the determination of cocaine in human hair. The chromatographic analysis was carried out on a Hydro-RP C18 column, using a mobile phase containing a phosphate buffer (pH 3.0)-acetonitrile-methanol (75:15:10, v/v/v). Native cocaine fluorescence was monitored at 315nm while exciting at 230nm. Mirtazapine was used as the internal standard. Sample pre-treatment was carried out by incubative extraction with 0.1M HCl followed by solid-phase extraction with C2 cartridges. Good linearity was obtained over a working range of 0.3-100.0ng/mg. Both extraction yield (>89%) and precision values (R.S.D.<6.2%) were highly satisfactory. The method was successfully applied to hair samples collected from cocaine users. Thus, the method is suitable for the long-term monitoring of cocaine use by means of hair testing.