Integral UV Spectrophotometric Method for the Determination of Loperamide Hydrochloride in Industrial Equipment Cleaning Rinse Waters

Introduction: Loperamide is a widely produced generic medication included in the WHO list of essential medicines. Analysing trace amounts of the drug on the surfaces of equip-ment and in industrial cleaning rinse waters is crucial in pharmaceutical manufacturing. This pa-per presents a method for measuring loperamide hydrochloride in industrial equipment rinse wa-ters using multiwavelength derivative UV spectrophotometry and the calculation of areas under the curves. Methods: Spectra were obtained in an aqueous solution without prior adjustments to the pH. The spectra were numerically integrated over the wavelength range of 218 to 238 nm. The quantifica-tion of loperamide is conducted through the use of a regression equation. Results: The technique allows for the measurement of loperamide hydrochloride in solution with-in the concentration range of 1-60 mg/L, with a limit of detection of 1.9 mg/L and a limit of quan-tification of 5.8 mg/L. The relative uncertainties are not greater than 3% for the analysis of solu-tions from active pharmaceutical ingredients and not greater than 7% for the analysis of model rinse waters. The relative standard deviations are up to 3% for solutions from active pharmaceuti-cal ingredients and up to 7% for model rinse waters. Discussion: The analytical performance of the method is comparable to existing methods of spec-trophotometric analysis of loperamide. The advantages of this method are that it requires minimal sample preparation, does not use toxic organic solvents, and does not involve complex analytical instrumentation, making it suitable for the routine analysis of loperamide in rinse waters from in-dustrial equipment cleaning. Conclusion: The spectrophotometric methods of determination of loperamide hydrochloride in aqueous medium using the derivative spectroscopy and the area under the curve method are pro-posed for the analysis of the rinse waters from industrial equipment cleaning.