High-performance liquid chromatographic determination of phenylephrine in human serum with coulometric detection

A high-performance liquid chromatographic method for the determination of phenylephrine (PE) in human serum using coulometric detection is described. PE and internal standard, orciprenaline, were extracted from serum by solid-phase extraction and separation achieved on a coupled column system consisting of two C18 cartridge columns (250 x 4.6 mm I.D. coupled to a shorter 50 x 4.6 mm I.D. column) using a mobile phase of methanol-50 mM phosphate buffer (pH 3.2; 10:90) at 36 degrees C. Dual electrode coulometric detection was used in the "oxidative screen" mode. Calibration curves were linear over the range 0.3-4 ng/ml with a limit of quantification (LOQ) of 0.35 ng/ml. The method has a greater degree of sensitivity, precision and accuracy compared to previously published methods for PE and is suitable for use in pharmacokinetic and bioequivalence studies in humans.