Determination of cocaine and its metabolites in blood serum by liquid chromatography coupled to tandem mass spectrometry (LC-MS/MS)

Abstract

The aim of the study was to evaluate the usefulness of liquid chromatography-tandem mass spectrometry for determination of cocaine and its metabolites (benzoylecgonine, ecgonine methyl ester) in biological material. Method. Cocaine and its metabolites were quantified using liquid chromatography coupled to tandem mass spectrometry (LC/MS/MS). Results. The extraction repeated twice with smaller portions of solvent showed higher efficiency and lower values of standard deviation that is why it was applied to further analysis. To increase sensitivity of LC/MS/MS method optimization of declustering potential was performed over 0-300V range and DP=100V was chosen. Collision energy for cocaine and benzoylecgonine was 25V and for ecgonine methyl ester was 22V. High resolution of the apparatus allowed to select narrow signal range for each compound: 185,135±0.025 Da for cocaine-d3, 182,120±0.025 Da for cocaine, 168,105±0.025 Da for benzoylecgonine and 182,125±0.025 Da for ecgonine methyl ester. Results obtained from analysis of two series of cocaine, benzoylecgonine and ecgonine methyl ester samples allowed to plot calibration curves within the range of 1-100 ng/ml which showed linearity. Conclusion. Obtained results allowed for identification and quantitative determination of cocaine and its metabolites (benzoylecgonine and ecgonine methyl ester) in human serum. Liquid chromatography-tandem mass spectrometry can find application in both forensic and clinical toxicology.