Solid-Phase Extraction in Conjunction with Matrix-Assisted Laser Desorption Ionization/Quadrupole Ion Trap Mass Spectrometry for the Determination of Benzoylecgonine in Urine

A matrix-assisted laser desorption ionization/quadrupole ion trap/mass spectrometer (MALDI-QIT-MS) system is evaluated for the rapid analysis of benzoylecgonine, a cocaine metabolite, from human urine after solid-phase extraction (SPE). Collisionally activated dissociation (CAD) is utilized to provide unambiguous confirmation of benzyolecgonine. In addition, MALDI-QIT-MS is shown to be a viable, rapid quantitative method of analysis for benzoylecgonine with the inclusion of a deuterated benzoylecgonine internal standard. Linearity was established from 1 to 10 μg/mL of benzoylecgonine in urine. A clinical urine sample known positive for benzoylecgonine was analyzed by MALDI-QIT-MS. The results indicate a mean concentration of 6.2 μg/mL [7.4% relative standard deviation (RSD), n = 3] of benzoylecgonine by the MALDI method, which is in good agreement with the result of 7.1 μg/mL (7.0% RSD, n = 3) obtained by a standard gas chromatography (GC)-MS procedure. Therefore, the MALDI method is demonstrated to be a rapid method for the quantitation of benzoylecgonine without post-SPE derivatization and chromatographic separation. Finally, the MALDI method is briefly extended to another class of analyte, methadone, and [(±)-2-ethyl-1,5-dimethyl-3,3-diphenyl-pyrrolinium] (EDDP), a methadone metabolite, to demonstrate that the technique holds potential for a wide range of analytes.