Determination of pseudoephedrine hydrochloride and carbinoxamine maleate in combination drug formulation by liquid chromatography.

An isocratic, reversed-phase liquid chromatographic (LC) method was developed for simultaneous determination of pseudoephedrine hydrochloride (I) and carbinoxamine maleate (II) in a pharmaceutical dosage form. Analysis was conducted on a CN column (10 microns), with a mobile phase consisting of acetonitrile-methanol-phosphate buffer (pH 5.3)-water (140 + 170 + 40 + 100) and at a detection wavelength of 262 nm. The method was validated for linearity, precision, system reproducibility, and accuracy. Recoveries at 80-120% of labeled claim ranged from 97.4 to 100.7% and from 98.5 to 100.2% for I and II, respectively. Results were linear (correlation coefficient, r > 0.9995 for I in the range 250-750 micrograms/mL and r > 0.9999 for II in the range 20-60 micrograms/mL.