High-performance liquid chromatographic determination of phenylpropanolamine in human plasma and urine, using column switching combined with ion-pair chromatography.

A highly sensitive and selective high-performance liquid chromatographic method with ultraviolet detection at 205 nm, without prior derivatization, is described for the determination of phenylpropanolamine in human plasma and urine. The method involved extraction of plasma or urine at a basic pH with diethyl ether, and chromatographic analysis using column switching combined with ion-pair chromatography. In the first octadecylsilica column, the drug was preseparated from endogenous substances in samples by ion-pair chromatography. After column switching, in the second octadecylsilica column, the heart-cut fraction containing the analyte was further separated by reversed-phase chromatography. The detection limits were 0.4 ng/ml in plasma and 8 ng/ml in urine, both at a single-to-noise ratio of 3. The method was applied to the determination of the drug in plasma and urine after oral administration of 25 mg of phenylpropanolamine hydrochloride in water to a healthy human volunteer.