Reversed-phase high-performance liquid chromatographic determination of cocaine in plasma and human hair with direct fluorimetric detection.

A simple, but sensitive and specific, high-performance liquid chromatographic assay for cocaine with direct fluorimetric detection, particularly intended for the routine analysis of hair and blood samples, is described. Benzoylecgonine, eluting before cocaine in a completely resolved peak, is also detectable. Detection is based on the weak native fluorescence of cocaine and benzoylecgonine, depending on the benzene ring present in both molecules. Hair samples (20-200 mg) were incubated overnight in 2 ml of 0.25 M HCl at 45 degrees C and extracted with a commercial liquid-liquid method; the dried residue reconstituted with 500 microliters of 0.05 M NaH2 PO4 (PH 5.2) was injected. Blood plasma samples (200 microliters) were mixed with 150 microliters of 0.1 M Na2 HPO4 (pH 8.9) and extracted with 5 ml of chloroform-2-propanol (9:1); the organic phase was evaporated and the residue dissolved and injected as above. Isocratic reversed-phase liquid chromatography was carried out on a column (150 x 4.6 mm I.D.) packed with spherical 5-microns poly(styrene-divinylbenzene) particles; the mobile phase was 0.1 M potassium phosphate (pH 3)-methanol-tetrahydrofuran (70:25:5). The excitation and emission wavelengths were set at 230 and 315 nm, respectively. Under the described conditions, cocaine eluted in a symmetrical peak with a capacity factor of about 5. The limit of detection was about 1 ng/ml (0.2 ng injected), with a signal-to-noise ratio of 3.(ABSTRACT TRUNCATED AT 250 WORDS)