A comparative study of the ratio spectra derivative spectrophotometry, Vierordt's method and high-performance liquid chromatography applied to the simultaneous analysis of caffeine and paracetamol in tablets.

Two spectrophotometric methods and high-performance liquid chromatography were proposed for the simultaneous analysis of caffeine and paracetamol in a tablet formulation. The ratio spectra derivative method is based on the use of the analytical signals obtained by measuring at 267.9 and 291.0 nm for caffeine and 237.0 and 251.8 nm for paracetamol in the first derivative of the ratio spectra. Calibration graphs were prepared in the range 4-40 microg/ml for caffeine and 8-48 microg/ml for paracetamol. In Vierordt's method, A1(1) (1%, 1cm) values of paracetamol and caffeine were determined at 242.9 and 273.0 nm in zero-order spectra. The matrix for A1(1) (1%, 1cm) values was written and the amounts of both drugs were calculated by means of the program 'Matlab' software. The results obtained by these spectrophotometric methods were compared with the results of HPLC method.