Fluorometric determination of phenylephrine hydrochloride by liquid chromatography in human plasma

A sensitive method is described for the rapid determination of phenylephrine hydrochloride in human plasma. Phenylephrine was analyzed using high-performance liquid chromatography (HPLC) with fluorecence detection at excitation and emission wavelengths of 270 and 305 nm, respectively. A retention time of approximately 4.25 min was observed on chromatograms. Drug was separated from interfering plasma components by the use of disposable solid-phase extraction columns. Linear standard curves were constructed from drug concentrations of 0.5-5.0 and 2.5-80 ng/mL, for which an average recovery of 76-78% was obtained. Phenylephrine could be quantitatively measured at levels as low as 0.5 ng/mL. An assay precision (CV) of 23.6 and 15.9% was obtained at the lower sensitivities of 0.5 and 1.0 ng/mL, respectively. An example of the method was given for analysis of human plasma levels of drug following topical application of two drops of 2.5% aqueous or 10% viscous opthalmic solution to the eyes of two subjects.