Validated UHPLC–MS/MS assay for quantitative determination of etoposide, gemcitabine, vinorelbine and their metabolites in patients with lung cancer

A fully valid UHPLC–MS/MS method was developed for the determination of etoposide, gemcitabine, vinorelbine and their metabolites (etoposide catechol, 2′,2′‐difluorodeoxyuridine and 4‐O‐deacetylvinorelbine) in human plasma. The multiple reaction monitoring mode was performed with an electrospray ionization interface operating in both the positive and negative ion modes per compound. The method required only 100 μL plasma with a one‐step simple de‐proteinization procedure, and a short run time of 7.5 min per sample. A Waters ACQUITY UPLC HSS T3 column (2.1 × 100 mm, 1.8 μm) provided chromatographic separation of analytes using a binary mobile phase gradient (A, 0.1% formic acid in acetonitrile, v/v; B, 0.1% formic acid in water, v/v). Linear coefficients of correlation were >0.995 for all analytes. The relative deviation of this method was