Abstract: Objective To establish a liquid chromatography-tandem mass spectrometry(LC-MS/MS) method for the simultaneous analysis of cocaine(COC) and its metabolite benzoylecgonine(BZE) in urine samples.Methods A single dose of COC(10 mg/kg) was injected intraperitoneally into guinea pigs and urine samples were collected for 7 days.The urine samples were extracted by auto solid phase extraction(SPE),separated by the Allure PFP propyl column with a mobile phase consisting of methanol and 20 mmol/L ammonium acetate buffer 0.1% formic acid(80:20,V/V),and then analyzed by LC-MS/MS.Multiple reaction monitoring(MRM) mode was used to analyze COC(m/z 304.2→182.3,m/z 304.2→150.1) and BZE(m/z 290.2→168.3,m/z 290.2→105.0).Results COC and BZE showed a fairly good linearity over the range of 2.0～100 ng/mL(r=0.999 5).The detection limit was 0.5 ng/mL.The recovery rate was greater than 90% and the deviation of intra-and inter-day precision was less than 6%.BZE was the major target detected in urine samples,and its detection window was longer than COC.Conclusion This newly developed method shows high sensitivity and selectivity,and is suitable for the simultaneous analysis of cocaine and benzoylecgonine in urine samples.

Key words: forensic toxicology, chromatography, high pressure liquid, tandem mass spectrometry, solid phase extraction, urine, cocaine, benzoylecgonine