Abstract:

A facile method has been set up for the determination of cocaine(COC) and its metabolite ecgonine methyl ester(EME) in human urine by means of gas chromatography(GC) with a flame ionization detector(FID). The urine samples were prepared by liquid-liquid extraction(LLE). To improve the extraction efficiency, the experimental parameters of LLE, including extraction solvent and its amount, pH value of the urine sample and extraction time were investigated. The optimized conditions are:8.0 mL of chloroform-isopropanol(volume ratio 9∶1), was used extractant, the pH value of urine sample is around 9.5, the extraction temperature and time are 40 ℃ and 6 min, respectively. The intra-day precisions of COC and EME were 1.73% and 1.44% while the inter-day precisions of COC and EME were 2.57% and 2.89%, respectively. The limits of detection(LOD) for both were 0.04 mg/L. The derivatization of COC and EME in traditional detection process could be bypassed in this protocol. The results indicate that the developed method is rapid, accurate and sensitive, which can be used for the simultaneous determinations of COC and EME in urine samples for forensic applications.

Key words: liquid-liquid extraction, gas chromatography, cocaine, ecgonine methyl ester, urine