HPLC-F determination of cocaine in human hair after solid phase extraction

Cocaine (3-(benzoyloxy)-8-methyl-8-azabicyclo[3.2.1]octane-2-carboxylic acid methyl ester, COC) is one of the most widespread abuse drugs in the world. In the last few years, both the number of consumers and the total amount of COC consumed have risen dramatically in most countries, thus aggravating several health and social problems. In fact, acute cocaine use produces very pleasant feelings of well-being, lack of weariness and euphoria, but it is powerfully addictive and can cause severe acute and chronic health effects, such as infarction, brain stroke, disphoria, depressive syndrome and psychoses. For these reasons, it is important to detect COC abusers. Hair analysis is perfectly suitable for this purpose: in fact, the hair matrix absorbs COC and traps it into its structure. The resulting hair concentrations can also be related to the time elapsed since the drug intake, as hair has an almost constant growth rate. This allows a complete and constant monitoring of drug use to be carried out with few, infrequent and non-invasive samplings. Of course, to perform this kind of monitoring, reliable and easily applicable analytical methods are needed. An original HPLC method coupled to spectrofluorimetric detection has been developed for the analysis of COC in human hair. It is sensitive, reliable and uses easily available instrumentation. The analyte and the Internal Standard mirtazapine are separated on a reversed-phase C18 column, using a mixture of methanol, acetonitrile and an acidic phosphate buffer (10/15/75, v/v/v) as the mobile phase. Fluorimetric detection is carried out at excitation wavelength = 230 nm, emission wavelength = 315 nm. The hair sample pre-treatment is carried out by solid-phase extraction (SPE) using C2 cartridges, after digestion of the finely cut hairs (1-mm length) by extractive incubation in HCl at controlled temperature. This procedure gives good extraction yield values (> 80%). From these preliminary results, the method for the monitoring of COC intake, using human hair as the sample matrix, seems to be promising.