Determination of Plasma Pseudo-Ephedrine by Fluorescence Detection and High Performance Liquid Chromatography

A sensitive and specific high-performance liquid chromatographic method has been developed for the determination of pseudoephedrine in plasma. The assay was based on the production of a highly fluorescent derivative of pseudoephedrine using 4-chloro-7-nitrobenzo-2, 1, 3-oxadiazole (NBD-Cl) as the derivatization agent. The fluorescent derivatives were separated using normal phase liquid chromatography after an automated, column-switching, sample clean-up procedure. Pseudoephedrine determination was accurate and precise at concentrations as low as 10 nanograms per milliliter of plasma. The chromatographic step separated derivatives of pseudoephedrine from those of norpseudoephedrine and several other amines. Measurement of pseudoephedrine concentrations in plasma following a single 120 milligram oral dose is illustrated.