HIGH-SENSITIVITY LOW-COST METHODS FOR DETERMINATION OF COCAINE IN HAIR - HIGH-PERFORMANCE LIQUID-CHROMATOGRAPHY AND CAPILLARY ELECTROPHORESIS

Free solution capillary electrophoresis and high performance liquid ch romatography were applied to the analysis of cocaine in hair. Capillar y electrophoresis conditions were as follows. Background electrolyte: 0.050 M berate, pH 9.2; capillary: bare silica, 40 cm long, 50 mu m i. d.; potential: 15 kV; detection: UV at 238 nm wavelength. In addition, the separation was accomplished in a 50 cm x 75 mu m capillary with a n instrument with a photodiode array detector, recording on-line UV sp ectra of peaks from 200 to 400 nm. The isocratic high performance liqu id chromatographic method with fluorimetric detection used 230 nm (ex. ) and 315 nm (em.) wavelengths. Cocaine separation was carried out und er conditions summarized as follows: column packed with spherical poly styrene-divinylbenzene 5 mu m particles, mobile phase 0.1 M potassium phosphate (pH 3.0)/methanol/THF (70:25:5) at a flow rate of 0.5 ml/min and at room temperature. Liquid-liquid and solid-liquid sample prepar ation methods were used. Typically, levels of cocaine in hair as low a s 0.15-0.30 ng/mg were detected by capillary electrophoresis, while HP LC allowed the determination of concentrations lower by one order of m agnitude (0.015 ng/mg). Intra- and inter-assay precision data of the t wo techniques were comparable and characterized by relative standard d eviations in the range from 3 to 7%. On the other hand, the sample thr oughput of capillary electrophoresis (7-10 injections/h) was higher th an high performance liquid chromatography (2 injections/h). A good cor relation of the results (r(2) = 0.92) between the two techniques was o bserved in the assay of real cases.