Spectrophotometric Determination of Mebendazole using Diazotization Reaction and Coupling with m-Aminophenol Reagent

A simple and sensitive spectrophotometric method has been developed for the determination of mebendazole (MBZ) in it's pure and tablet form. The method is based on alkaline hydrolysis of MBZ with sodium hydroxide to give primary amine product which reacts with sodium nitrite in an acidic medium (hydrochloric acid) to yield diazotized mebendazole (D-MBZ) which is coupling with m-aminophenol reagent (mAP) to form an azo dye. The absorbance of the azo dye for this suggested method (yellow dye) has been measured at 360 nm. Beer's law for this proposed method is in the range of (0.5-20 g.ml-1), the molar absorptivity value is 1.63104 L.mol-1.cm-1 and the Sandell's value index is calculated and equal to 0.018 g.cm- 2. Also, the limit of detection and the limit of quantification are calculated and equal to 0.1718 g.ml-1 and 0.5726g.ml-1 respectively. The ratio of the formed azo dye [D-MBZ: mAP] is [2: 1].