A Novel, Stability-Indicating RP-HPLC Method for Simultaneous Estimation of Assay and Organic Impurities of Pyridostigmine Bromide and Assay of Sodium Benzoate in Liquid Oral Formulation

A reverse phase-novel HPLC stability-indicating method was developed for simultaneous estimation of the assay and organic impurities of pyridostigmine bromide, and an assay of sodium benzoate in pyridostigmine bromide oral solution. The method was developed by using HPLC with an isocratic program and a reverse-phase column of Phenomenex prodigy ODS C18, 150 mm 4.6 mm, i.d. 5.0 μm particle size with a mobile phase containing pH 2.0 sodium dodecyl sulfate buffer and acetonitrile in the ratio of 67:33 (v/v) with a flow rate of 1.0 mL/min, a column temperature of 25°C, with a UV wavelength detection at 222 nm, and injection volume of 20 μL. The modern research represents a concomitant single HPLC method. The retention time of pyridostigmine bromide and its degradation impurities pyridostigmine RC-A, chemically named pyridin-3-yl dimethylcarbamate and pyridostigmine RC-B (3-hydroxy-1-methylpyridin-1-ium bromide), is about 15.8, 12.8, and 14.5 min respectively. The assay and impurity method were validated as per USP , and per International Conference on Harmonization guidelines. The method is determined to be suitable for estimating the assay and impurities of active (Pyridostigmine Bromide) and assay of preservative (Sodium Benzoate) in the pharmaceutical drug product.