High-performance liquid chromatographic method development and validation for the simultaneous quantitation of naproxen sodium and pseudoephedrine hydrochloride impurities

A reversed-phase high-performance liquid chromatographic procedure for the simultaneous determination of impurities associated with pseudoephedrine hydrochloride (PSEH) and naproxen sodium (NapNa) is developed and validated. The method is developed using a Waters Spherisorb cyano column (5 μm, 250 × 4.6 mm). An isocratic elution in a water-acetonitrile-methanol-triethylamine mixture (850:75:75:5) is adjusted to a pH of 3.7 ± 0.02 with formic acid as the mobile phase. The UV detection was set at 260 nm, and the wavelength was switched to 235 nm before the elution of the last component, 2-ethyl-6-methoxy-naphthalene (EMN). The method is shown to be linear at a concentration range of 0.24 to 1.92 μg/mL for benzaldehyde, benzoic acid, and 2-(methylamino)-propiophenone hydrochloride, which are known impurities of PSEH. The NapNa impurities, 2-(6′-hydroxy-2′-naphthyl) propionic acid, 2-hydroxy-6-methoxy-naphthalene, 1-(6′-methoxy-2′-naphthyl) ethanol, 2-acetyl-6-methoxy-naphthalene, and EMN are also demonstrated to be linear at a concentration range of 0.44 to 3.52 μg/mL. Under the chromatographic conditions of the method, all impurities are resolved from the active components.