A rapid and sensitive RP-HPLC method with UV detection at 227 nm for routine analysis of washed MLs (mother liquors) from equipment after manufacturing and thereby cleaning of ibutilide fumarate active pharmaceutical ingredient was developed. Chromatography was performed with mobile phase containing a mixture of aqueous 0.01 M potassium dihydrogen phosphate (KH2PO4) and acetonitrile. The gradient elution was developed for better and optimized results. The developed method was validated for precision which includes system precision and method precision, accuracy, intra-day and using different system and finally linearity studies from 0.4 to 150%. The method is ascertained to be having good repeatability and reproducibility. The %RSD for method precision (5 different preparations at test concentration) was observed to be 1.36, wherein the system precision (6 repeated injections of same preparation) was observed to be 0.33. The % recovery from ‘Accuracy’ studies yielded the recovery of 99-100% which indicates the capability of the method. The linearity of the method was studied right from 0.4 to 150% which shows the method is quite linear with a correlation coefficient of 0.9998. The proposed method was simple, highly sensitive, precise, and accurate.The retention time less than 15 min, indicated that the method is useful for routine testing of washed MLs from equipment after manufacturing and cleaning of ibutilide fumarate.