Comparative evaluation of four spectrophotometric methods for the simultaneous determination of paracetamol and phenylephrine hydrochloride in fixed dose pharmaceutical formulations

Chavada et al / Physical Chemistry 17(1) (2015) 6-15 7 2004; Sirajuddin et al., 2007) electrochemical (Fan et al., 2011; Ghadimi et al., 2013; Özcan and Sahin, 2011; Khaskheli et al., 2013) and chromatographic techniques (McEvoy et al., 2007; Mostafa, 2010; Németh, 2008). The rationale for the present work was to develop and validate four accurate, precise, simple and economical spectrophotometric methods for the simultaneous determination of PAR and PHE in their combined dosage forms. The methods have been developed and validated as per the ICH guidelines (ICH Guidelines, 2005) for simultaneous estimation of PAR and PHE in synthetic mixtures as well as in pharmaceutical preparations. In addition, all the four methods showed absence of interferences due to presence of commonly used excipients and additives. MATERIALS AND METHODS Instrumentation and analysis conditions A Shimadzu UV-1700 double beam spectrophotometer (Kyoto, Japan) with matched 10 mm quartz cells was used for spectral measurements. The wavelength accuracy was within ± 0.5 nm and a bandwidth of 1 nm was kept for all the methods. Data processing was done with Shimadzu UV PC software version 2.0. The spectra were recorded at a scan speed of 400 nm min -1 . Weighing of samples was done on a Sartorius GD503 (Bradford, MA, USA) analytical balance having a readability of 0.0001 g. For studying the ruggedness of the methods, HITACHI 3210 UV-Visible Spectrophotometer (Tokyo, Japan) was also used. Chemicals and materials Reference standards of paracetamol (99.38%) and phenylephrine hydrochloride (99.13%) were obtained from Clearsynth Labs (P) Ltd. (Mumbai, India). Spectroscopic grade methanol was procured from E. Merck (Mumbai, India). Five pharmaceutical formulations of PAR and PHE, Contac C ® (500 mg PAR + 10 mg PHE tablet, GlaxoSmithKline, PA, USA), Robitussin ® nasal relief’ (325 mg PAR + 5 mg PHE tablet, Pfizer, Madison, NJ, USA), Excedrin ® Sinus Headache (325 mg PAR + 5 mg PHE tablet, Novartis Farmaceutica, S.A. DE C.V., México), Feniapal ® (100 mg PAR + 5 mg PHE capsule, Novartis Farmaceutica, S.A. De C.V., México) and Vicks ® DayQuil Sinex ® (325 mg PAR + 5 mg PHE capsule, Procter & Gamble Hygiene & Healthcare Ltd., LA, USA) were purchased from a local pharmacy. Standard stock and calibrations standards Separate stock solutions of PAR and PHE equivalent to 200 μg mL -1 were prepared by dissolving 20 mg of each reference standard in 100 mL methanol. Calibration standards for PAR and PHE were prepared in the concentration range of 1.0-12 μg mL -1 for PAR and 5.0-25 μg mL -1 for PHE from their respective stock solutions in methanol. Graphical method This method is generally useful when the individual spectra are not well resolved (Blanco et al., 1989). It requires absorbance measurement on multiple wavelengths for standard solutions of each component (APAR and APHE) and the synthetic sample mixture (AMIX). The mathematical expression for the method is given the equation 1,