Validation of urine drug-of-abuse testing methods for ketobemidone using thin-layer chromatography and liquid chromatography-electrospray mass spectrometry

High-performance thin-layer chromatography (TLC) with visual detection (post-chromatographic derivatization) was used in screening for the drug kerobemidone in human urine samples. High-performance liquid chromatography with electrospray mass spectrometry (LC-ESI-MS) was used for final confirmation of the result. The clean-up was performed by mixed-mode solid-phase extraction, and nalorphine was used as internal standard. A screening cut-off for TLC was established at 0.2 mu g/ml. The mean recovery for LC-MS was 91% (n=60) with coefficients of variation (C.V.) in the range of 7 to 16%. Qualifying fragment ions of ketobemidone (m/z 190, 201 and 230) were generated by up front collision-induced dissociation (CID) on a single quadrupole instrument. Relative ion intensities were within +/-15% deviation compared with standards in the same batch. The limit of detection for LC-MS was 0.025 mu g/ml. Positive clinical samples from drug abusers (n=10) had concentrations in the range 0.07 to 3.2 mu g/ml, which could be determined by LC-MS without matrix interference. During screening of unknown clinical samples (n=27) the results from TLC was in agreement with LC-MS data. After acid hydrolysis of conjugates in clinical samples the analyte response of ketobemidone and norketobemidone was increased by a factor of approximately two and twelve, respectively. A qualitative GC-MS technique was demonstrated for the detection of the spasmolyticum A29 (N,N-dimethyl-4,4-diphenyl-3-buten-2-amine), which can be found in a preparation combined with ketobemidone (Ketogan). (C) 1999 Elsevier Science B.V. All rights reserved.