Sensitive Spectrophotometric Method for Quantitation of Guaifenesin and Dropropizine in Their Dosage Forms

Guaifenesin and dropropizine were analyzed through oxidation with periodic acid to give formaldehyde which was allowed to condense with 4-Amino-5-hydrazino-4H [1,2,4]-triazole-3-thiol (AHTT). The condensation product was further oxidized to yield a purple colored compound with maximum absorption at 550？nm. Beer's law was obeyed in the range of 5–45？ g for guaifenesin and 10–80？ g for dropropizine. Both drugs were also successfully determined in their dosage forms. 1. Introduction Guaifenesin (GF), 3-(2-Methoxyphenoxy)-1,2-propanediol; is reported to increase the volume and reduce the viscosity of tenacious sputum and is used as expectorant for productive cough [1]. Different methods have been reported for the analysis of GF including HPLC [2–8], GC [9, 10], capillary electrophoresis mass spectrometry [11], X-ray diffraction [12], voltammetry [13]. Dropropizine (DP), 3-(4-Phenyl-1-piperazinyl)-1,2-propanediol, is a cough suppressant reported to have a peripheral action in nonproductive cough [1]. Only two GC-mass spectrometry methods have been reported for the determination of DP in biological fluids [14, 15] in addition to a manufacturer procedure that involves the determination of dropropizine by measuring its UV absorbance at 237？nm in 0.05？N HCl (personal contact): Bromhexine HCl (BR), 2-Amino-3,5-dibromo-N-cyclohexyl-N-methylbenzylamine hydrochloride; N-(2-Amino-3,5-dibromobenzyl)-N-methylcyclohexylamine hydrochloride: The aim of the present paper is to develop a simple and accurate method for the determination of dropropizine and guaifenesin that permits their analysis in dosage forms without interference from excipients and other coformulated drugs. 2. Experimental 2.1. Chemicals and Reagents Purpald or 4-Amino-5-hydrazino-4H [ ]-triazole-3-thiol reagent (AHTT) (Sigma-Aldrich) was prepared as 0.5% in 0.5？M hydrochloric acid. Periodic acid (Winlab, UK.) was prepared as 1？ solution in 0.2？M potassium hydroxide. HPLC grade acetonitrile was from Fisher Scientific, UK. Potassium dihydrogen phosphate was from Sigma-Aldrich Chemie, Germany. All other chemicals used were of analytical grade and water was freshly distilled. 2.2. Materials Reference standard guaifenesin (GF), dropropizine (DP) and bromhexine HCl (BR) were kindly supplied by Rameda Co. for pharmaceutical industries and diagnostic reagents, EVA Pharma for pharmaceutical and medical appliances and EVA Pharma for pharmaceutical and medical appliances, respectively. 2.3. Pharmaceutical Preparations Muclear Capsules: It is a product of Rameda Co., Batch No. 08455, claimed to contain 100？mg