Validated procedure for simultaneous trace level determination of the anti-cancer agent gemcitabine and its metabolite in human urine by high-performance liquid chromatography with tandem mass spectrometry

A sensitive, accurate and reproducible procedure has been developed for the quantitative determination of gemcitabine (2′,2′ -difluorodeoxycytidine, dFdC) and its metabolite 2′,2′ -difluorodeoxyuridine (2dFdU) in human urine. The samples (2 mL) were extracted by solid-phase extraction (SPE) and analyzed by reversed-phase high-performance liquid chromatography coupled with tandem mass spectrometry (HPLC/MS/MS), operating in multiple reaction monitoring (MRM mode). This procedure was validated using 2′-deoxycytidine as internal standard (IS). The urine assay was linear over the range 0-50 μg/L, with a limit of quantification (LLOQ) of 0.2 μg/L for gemcitabine and 1.0 μg/L for the metabolite. The respective limits of detection (LODs) for dFdC and 2dFdU were 0.05 and 0.3 μg/L. The precision and accuracy of the assay were determined on three different days. The within-series precision was found to be always less than 8. 5 and 12.7% for gemcitabine and 2dFdU, respectively. The overall precision expressed as relative standard deviation (CVr) was always less than 7.1% for both analytes. The recovery of gemcitabine was always greater than 90% with a CVr