Stereospecific high-performance liquid chromatographic assay for the enantiomers of phenylpropanolamine in human plasma.

A stereospecific high-performance liquid chromatographic assay for the enantiomers of phenylpropanolamine (PPA) in human plasma has been developed. The method is based on reaction of extracted PPA with the chiral derivatizing agent 2,3,4,6-tetra-O-acetyl-beta-D-glucopyranosyl isothiocyanate to form diastereomeric thiourea derivatives. These thiourea derivatives are stable for at least 24 h, readily separable by reversed-phase chromatography, and amenable to ultraviolet detection at 254 nm. Standard curves for each of the PPA enantiomers are linear over the concentration range 10-250 micrograms/L. Over the approximate range of the standard curve, precision (intra- and interday) ranged from 2.2-7.0% while accuracy ranged from 99.2-107.3%. The method has been shown to be free from interference from endogenous plasma constituents and from a range of drugs containing a primary or secondary amine function. Individual PPA enantiomer plasma concentration-time profiles measured for a subject administered racemic PPA are included to demonstrate the utility of the assay.