A STABILITY-INDICATING HPLC METHOD FOR THE DETERMINATION OF NAPHAZOLINE AND ITS DEGRADATION PRODUCT AND METHYL PARAHYDROXYBENZOATE IN PHARMACEUTICAL PREPARATIONS

A simple, rapid, selective, accurate, and stability-indicating HPLC method for the simultaneous determination of naphazoline and methyl parahydroxybenzoate in pharmaceutical preparations was developed and validated. The method employs a BDS Hypersil C18 column (5 μm; 150 x 4 mm), a mobile phase containing methanol -0.05M triethylamine plus 10% methanol pH 3 with o-phosphoric acid (30:70, v/v), with a flow rate of 1 mL/min and detection at 254 nm. All the validation parameters (linearity, specificity, accuracy, repeatability, LOD/LOQ) were within the acceptance range and met the ICH Q2(R1) guideline. The stability indicating capability of this method has been demonstrated by separating degradation products as 1-naphthylacetylethylenediamine (impurity A) and 1-naphthylacetic acid (impurity B). Stability tests were performed under alkaline, acidic, neutral, and oxidizing conditions, and with simulated sunlight under standardized conditions in a sun test irradiation chamber. The proposed method was applied for routine quality control showing the obtained assay results for various marketed preparations and for the in-house formulation to be in good agreement with the declared amount. Compared with the pharmacopoeial method, shorter retention times and a superior resolving capability have been shown.