Joliana Fawzy

BACKGROUND: Chromatographic behavior of different substances in normal and reversed phases is an interesting area in the scientific community.

OBJECTIVE: The work aimed to optimize and validate chromatographic separation methods for simultaneous determination of paracetamol (PAR) and phenylephrine HCl (PHE) in the presence of PAR impurities, namely p-aminophenol, p-nitrophenol, acetanilide, and p-chloroacetanilide with further quantification of these toxic impurities.

METHODS: TLC method based on normal phase separation was carried out on aluminum sheets of silica gel 60 F254 using ethanol:chloroform:ammonia as a developing system, followed by densitometric measurements. While HPLC is based on reversed phase separation using a C18 column against acetonitrile:phosphate buffer pH 5 as a mobile phase.

RESULTS: PAR and PHE were determined by the TLC-densitometric method in concentration ranges of 3-25 and 0.1-3 µg/band, respectively, and determined by the HPLC method over concentration ranges of 5-400 and 2-80 µg/mL, respectively. Both methods were optimized and validated. Furthermore, they were successfully applied for pharmaceutical formulations with precision <2%. Moreover, results of a statistical comparison with the official methods confirm the methods' validity claims.

CONCLUSION: Two eco-friendly chromatographic methods were developed to determine PAR and PHE in their binary mixtures, pharmaceutical formulations, and in the presence of PAR-related impurities with further quantification of these toxic impurities.

HIGHLIGHTS: These simple chromatographic methods are the first methods developed for simultaneous determination of PAR and PHE in the presence of PAR-related impurities.

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.