Spectrophotometric Determination of Thymol in Pharmaceutical Preparation via Diazotization Reaction with 4-aminoacetophenone

A simple and sensitive spectrophotometric method is proposed for the determination of thymol. The method is based on the coupling reaction of the drug with diazotised 4-aminoacetophenone reagent in alkaline medium to produce an intense red coloured water -soluble and stable azo dye which exhibits a maximum absorption at 502 nm. Beers low is obeyed over the concentration range 0.2 16 g/ml with a molar absorptivity of 2.89104 L.mol-1.cm-1. The limit of detection is 0.0216 g/ml and the limit of quantitation is 0.072 g/ml, average recovery is 101.6%, and RSD is less than 2.4%. The proposed method is applied successfully to the determination of thymol in pharmaceutical preparation.