Determination of dextropropoxyphene and nordextropropoxyphene in urine by liquid chromatography–electrospray ionization mass spectrometry

Dextropropoxyphene and nordextropropoxyphene were extracted from urine samples with mixed mode solid-phase extraction cartridges. After elution and evaporation to dryness, the eluate was dissolved in mobile phase and each sample was injected in a LC–ESI-MS system. Quantification was carried out in the selected ion monitoring mode. This article shows the possibility to analyse drugs of abuse substances in urine with a single quadrupole mass spectrometer if only a thorough work-up procedure and a sufficient chromatographic separation is accomplished. In order to enhance the fragmentation of the analytes, in-source fragmentation was carried out. One fragment and the pseudomolecular ion per analyte together with chromatographic retention times were sufficient to verify that the sought compound was found in the samples. In- and between day variation was lower than 10% and the recovery was well above 90%. The analytes were quantified in the range 100–10 000 ng/ml urine.