HPLC DETERMINATION OF N-METHYLETHANOLAMINE IN DIPHENHYDRAMINE HYDROCHLORIDE DRUG SUBSTANCE BY PRE-COLUMN DERIVATIZATION

N-Methylethanolamine is the side chain of the drug diphenhydramine hydrochloride. A sensitive high performance liquid chromatography method with pre-column derivatization was developed and validated for the determination of N-methylethanolamine impurity in diphenhydramine hydrochloride active pharmaceutical ingredient. HPLC method on column Cosmosil MS-II, C-18, 250 mm X 4.6 mm, particle size 5 μm with UV detector was used. The proposed method is specific, linear, accurate, rugged and precise. The calibration curves showed good linearity over the concentration range of 0.03 mg/g to 1.5 mg/g and the correlation coefficient was 0.999. Method had very low limit of detection (LOD) and limit of quantification (LOQ) as 0.01 mg/g and 0.03 mg/g, respectively, of the analyte. Accuracy was observed within 94.4% to 96.2%.