Simultaneous determination of cocaine/crack and its metabolites in oral fluid, urine and plasma by liquid chromatography-mass spectrometry and its application in drug users

IntroductionA single LC-MS equipment was used to validate three methods for simultaneously analyzing cocaine (COC), benzoylecgonine (BZE), cocaethylene (CE), anhydroecgonine methyl ester (AEME) and anhydroecgonine (AEC) in oral fluid (OF), urine and plasma.MethodsThe methods were carried out using a Kinetex HILIC column for polar compounds at 30 °C. Mobile phase with isocratic condition of acetonitrile: 13 mM ammonium acetate pH 6.0: methanol (55:35:10 v/v/v) at 0.8 mL/min flow rate was used.ResultsAfter buffer dilution (OF) and protein precipitation (urine and plasma), calibration curve ranges were 4.25-544 ng/mL for oral fluid and 5-320 ng/mL for urine and plasma with correlation coefficients (r) between 0.9947 and 0.9992. The lowest concentration of the calibration curves were the lower limit of quantification. No major matrix effect could be noted, demonstrating the efficiency of the cleaning procedure.DiscussionThe methods were fully validated and proved to be suitable for analysis of 124 cocaine and/or crack cocaine users. Among the subjects, 56.5% reported daily use of cocaine in the previous three months. Results show a high prevalence of the analytes, with BZE as the most prevalent (94 cases), followed by COC (93 cases), AEC (70 cases), CE (33 cases) and AEME (13 cases). In addition, the concentration of BZE in urine was higher compared to OF and plasma found in the real samples, showing the facility of accumulation in chronic users in matrices with a large detection window.