DETERMINATION OF COCAINE AND BENZOYLECGONINE IN HUMAN PLASMA BY LC-MS/MS

A high-throughput Liquid chromatography / Mass spectrometry / Mass spectrometry (LC/MS/MS) method for simultaneous quantification of cocaine (COC) and benzoylecgonine (BZE) in human plasma was elaborated. After the protein precipitation with methanol in the plasma samples, the analytes were separated on a Zorbax SB-C18 column under isocratic conditions using a 32:68 (v/v) mixture of methanol and 0.1 % formic acid in water at 45ºC, with a flow rate of 1 mL/min. The detection was in multiple reaction monitoring (MRM) mode (m/z 290 → m/z 168 for BZE and m/z 304 → m/z 182 for COC, respectively). Calibration curves were generated over the range of 20-2000 ng/mL for both BZE and COC (r> 0.992). In the laboratories that are not equipped with a LC/MS/MS system, the LC analysis of COC and BZE requires a previous isolation step. Therefore, the elaborated LC/MS/MS method was applied for the study of optimum experimental conditions for the isolation of COC and BZE from human plasma. Several solvent mixtures and solid-phase extraction (SPE) cartridges were tested at different pH values. The best results for both analytes were obtained by SPE on Oasis HLB cartridges (mean recovery o