Spectral manipulation of ratio data for simultaneous determination of binary mixture of Paracetamol and Phenylephrine Hydrochloride.

Three ratio spectra manipulating spectrophotometric methods have been developed for determination of Paracetamol (PAR) and Phenylephrine HCl (PHE) in bulk powder and in pharmaceutical formulation. Linear correlations were obtained over the concentration range of 1.0-25.0 µg/mL and 5.0-50.0 µg/mL for PAR and PHE, respectively. The first method is the ratio subtraction method (RS) coupled with constant multiplication (CM) in which PHE was determined by ratio subtraction and PAR was determined by constant multiplication. The second method is the ratio difference method (RD) which depends on measuring the difference between the amplitudes of the ratio spectra at two selected wavelengths. The third method is the first derivative of the ratio spectra (DD), which allows the determination of PAR at 238.8 and 243 nm and PHE at 213.2, 222.2, 271.8 and 286 nm. The proposed methods are simple, accurate and precise (RSD does not exceed 2%). The applicability of the proposed methods was successfully verified by the analysis of PAR and PHE in pharmaceutical formulation without interference of the dosage form additives. Furthermore, the developed methods were validated according to ICH guidelines, so they are considered to be potential competitors for the analysis of the mixture in quality control labs and pharmaceutical factories.