Mojdeh Sharifi - Islamic Azad University Shahr e Qods
Hossein Tavallali - Islamic Azad University Shahr e Qods

Derivative spectrophotometry offers a useful approach for the analysis of drugs in multi – component mixtures. In this study a first- derivative spectrophotometry method was used for simultaneouse determination of caffeine and paracetamol using the zero- crossing technique. The measurement we carried out at wavelengths of 287 and 236 nm for caffeine and paracetamol respectively. The method was found to be linear(r2 >0.9974) in the range of 1- 5 μg/ml for caffeine in the presence of 5 μg/ml paracetamol at 272 nm. The same linear correlation was also obtained (r2 >0.9965) in the range of 1- 6 μg/ml for paracetamol in the presence of 2 μg/ml of caffeine at 242 nm.The limit of determination was 0.57 and 0.6 μg/ml for caffeine and paracetamol respectively. The method was successfully applied for simultaneous determination of caffeine and paracetamol in pharmaceutical preparations without any interferences from excipients.Key wrds: simultaneouse determination, derivative spectrophotometry, zero- crossing technique, caffeine, paracetamol

simultaneouse determination, derivative spectrophotometry, zero- crossing technique, caffeine, paracetamol