Simultaneous Determination of Otilonium Bromide and Diazepam by First-Derivative Spectroscopy

A rapid, simple assay procedure was developed for simultaneous analysis of otilonium bromide, a smooth‐muscle relaxant, and diazepam in tablets containing 20mg of otilonium bromide and 2mg of diazepam (20:2 tablets) or 40mg of otilonium bromide and 2mg of diazepam (40:2 tablets) by “zero‐crossing” first‐derivative spectroscopy. The tablets were dissolved in 0.01N HCl, mixtures were centrifuged at 3500rpm (2472 × g) for 5 min, and first‐derivative spectra were recorded. The absolute values of the derivative were measured at 264nm for determination of otilonium bromide and between 406 and 408nm (380nm for analysis of 40:2 tablets) for determination of diazepam. The method is linear, quantitative, and reproducible and can also be used for the tablet dissolution test. Ten tablets of the same batch were analyzed by the described method and by a high‐performance liquid chromatographic method, and the results were in good agreement.