HPLC determination of polymyxin-B-sulphate, gramicidin and benzalkonium chloride in pharmaceutical formulations

A rapid and sensitive method is described for the determination of gramicidin, polymyxin-B-sulphate and benzalkonium chloride in pharmaceutical preparations using high-performance liquid chromatography. The analysis was performed on 5u-Nuclosil-cyano 250x4.6mm column, water [pH 1.9 with perchloric acid]: Acetonitrile: Isopropanol [60: 30: 15] as a mobile phase, detection at 214nm and at 35[degree]C. The method was applied on Neo-myxidin Eye Drops which contains the same concentrations of this mixture and the results are in agreement with manufacture's specification. With good accuracy and precision as shown from the percentage recovery and relative standard deviation from 0.2 to 1.64%