Determination of diazepam and otilonium bromide in pharmaceuticals by ratio-spectra derivative spectrophotometry

Binary mixtures of diazepam and otilonium bromide are analyzed by ratio-spectra first- and second-derivative spectrophotometry. The procedures are accurate, non-destructive and do not require any separation step. Calibration graphs are linear with zero-intercept up to 50 μg/ml, r ranging from 0.9996 to 0.9999. Working wavelengths in the first- and second-derivative mode, respectively, are: diazepam 247 nm and 231 nm, otilonium bromide 262 nm and 226 nm. Limits of detection (LOD) are 0.30 and 0.12 μg/ml for diazepam and 0.063 and 0.30 μg/ml for otilonium bromide. The methods were successfully applied for determining the two drugs in laboratory mixtures and in pharmaceutical products.