Spectrophotomeric Estimation of Thymol in Pure and Pharmaceutical Formulation with Diazotized 4-aminoacetophenone

A spectrophotometric method for the determination of trace amount of thymol in pure form and in mouth wash preparation has been proposed in this study. The method is based on the coupling reaction of thymol with diazotized 4-aminoacetophenone in alkaline medium to form an intense red water-soluble dye that is stable and has a maximum absorption at 487 nm. A graph of absorbance versus concentration show that Beers law is obeyed over the concentration range of 10-400 g /25mL ( 0.4- 16 ppm) with a molar absorptivity of 2.77104 L.mol-1 cm-1 and Sandell s sensitivity index of 0.005g/cm2. The method does not require neither temperature control nor solvent extraction step. The proposed method is successfully applied to the determination of thymol in mouth wash preparation.