Determination of 6-keto prostaglandin F1α and its metabolites in human plasma by LC–MS/MS

► A new HPLC–MS/MS method was developed and validated for the quantification. ► Improved selectivity in comparison to ligand-binding assays. ► First application to clinical trial samples obtained from a pharmacokinetic study. An HPLC–MS/MS method was developed and validated for the quantification of 6-keto prostaglandin F1α, the stable hydrolysis product of prostacyclin, and its metabolites 2,3-dinor-6-keto prostaglandin F1α and 6,15-diketo-13,14-dihydro prostaglandin F1α in human plasma. For sample preparation, a solid phase extraction step was combined with a column switching approach for analytes enrichment and further sample clean-up of the processed sample. The assay was validated in the concentration range 50.0–5000pg/mL for 6-keto prostaglandin F1α and 6,15-diketo-13,14-dihydro prostaglandin F1α, and 100–10,000pg/mL for 2,3-dinor-6-keto prostaglandin F1α. The inter-batch precision was better than 12.7%, 9.2%, and 9.4% for 6-keto prostaglandin F1α, 2,3-dinor-6-keto prostaglandin F1α, and 6,15-diketo-13,14-dihydro prostaglandin F1α, respectively. The inter-batch accuracy was between 97.3% and 100.8% for 6-keto prostaglandin F1α, between 97.5% and 103.0% for 2,3-dinor-6-keto prostaglandin F1α, and between 92.0% and 100.0% for 6,15-diketo-13,14-dihydro prostaglandin F1α. Further it has been demonstrated that the analytes were stable in plasma for 20h at room temperature, during three freeze-and-thaw cycles, for 96 days at −25°C storage temperature, and 50h in the autosampler tray at room temperature.