Simultaneous determination of four active components in a compound formulation by liquid chromatography

A rapid and accurate LC method is described for simultaneous determination of pseudoephedrine hydrochloride (PSE), acetammophen (AMP), dextromethorphen hydrobromide (DEX), and diphenhydramine hydrochloride (DPH) in a compound formulation. Chromatographic separation of the four drugs was achieved on a Hypersil CN column (150 mm x 4.6 mm, 5 μm particle) by use of a mobile phase comprising a mixture og 3 mM ion-pairing solution, 2% aqueous triethylamine solution, and 2 M phosphoric acid, 68:48:88 (v/v), pH 3.0, delivered at 1.0 mL min^-1. Compounds were detected at 215 nm and the run time was less than 10 min. The linearity, accuracy, and precision of the method were found to be acceptable over the concentration ranges 6.1-36.4 μg mL^-1 for PSE, 65.0-390.0 μg mL^-1 for AMP, 3.1-18.6 μg mL^-1 for DEX, and 5.0-30.0 μg mL^-1 for DPH.