Liquid Chromatographic and Potentiometric Methods for the Determination of Oxomemazine in Pharmaceutical Preparations

Simple and selective two different techniques are developed for the determination of oxomemazine in pharmaceutical preparations. A rapid (less than 6 min) and accurate high performance liquid chromatography(HPLC) method has been developed where chromatographic analysis is performed on Nova-Pak ® C 18 column (3.9 mm × 150 mm, 5 µm) with an ammonium formate buffer adjusted with formic acid to pH 3.0 and acetonitrile (75: 25, v/v) as a mobile phase, and detection at 235 nm. Good linearity (0.99, r 2 ), accuracy (≥ 99.20%), and precision (≤ 0.6 RSD) were obtained. Potentiometric measurements are based on tetrakis ( p -chlorophenyl) borate-oxomemazine ion-pair complex as an electroactive species incorporating in a plasticized poly vinyl chloride (PVC) membrane with o-nitrophenyl octyl ether ( o -NPOE) or dioctyl phthalate (DOP). The sensor exhibits fast and stable Nernstian response for oxomemazine over the concentration range of 1.0 × 10 -5 – 1.0 × 10 -2 mol L -1 and pH range of 3.5 - 6.0. The sensor shows reasonable selectivity towards oxomemazine hydrochloride over many cations. No significant interferences are caused by drug excipients and diluents. Results with an average recovery of 100.6% and a mean standard deviation of 0.77% of the nominal were obtained.