Development of a high-performance liquid chromatography–tandem mass spectrometry method for the determination of flurogestone acetate in ovine plasma

Flurogestone (FGA) is a synthetic progesterone, with a progestational action higher than that of progesterone itself. It is intended for vaginal use in large animals to induce oestrus synchronization. A quantitative method for the analysis of flurogestone acetate (FGA) in ovine plasma by high-performance liquid chromatography–tandem mass spectrometry (HPLC–MS/MS) has been developed. After the incorporation of megestrol acetate (MGA) as internal standard (IS) and followed by a liquid–liquid extraction from plasma, FGA and MGA were chromatographed using a reverse-phase HPLC column and detected by tandem mass spectrometry with a TurboIonSpray® source. Multiple reaction-monitoring (MRM) mode was used for the quantitative determination of FGA in ovine plasma. The precursor ions [M + H]+ at m/z 407.2 and 385.1 for FGA and MGA, respectively, produced product ions at m/z 267.1/285.1 for FGA and m/z 267.1/224.0 for MGA. The validated concentration range was 0.2–5.0 ng/ml based on 500 μl plasma aliquots. The lower limit of quantitation was 0.2 ng/ml. Fully validated selectivity, accuracy, precision and reproducibility criteria for routine use in pharmacokinetic studies were demonstrated.