Determination of ketobemidone and its metabolites in plasma and urine using solid-phase extraction and liquid chromatography-mass spectrometry

The authors developed a sensitive, specific, and rapid liquid chromatograph y-mass spectrometry (LC-MS) method for determining ketobemidone and its maj or metabolites in plasma and urine. The method involves a solid-phase extra ction, high-performance liquid chromatography (HPLC), and electrospray mass spectrometry. The limit of quantification for ketobemidone and norketobemi done was 3 nmol/L. Recovery rates for ketobemidone and norketobemidone were 84.8% and 81.1%, respectively. Coefficients of variation (CV) ranged from 2.8% to 9.5%. The method was used to determine ketobemidone and its major m etabolites in clinical samples from relevant patient groups.