Determination of Thymol in Pure and Pharmaceutical Preparation by Diazotization – Coupling Method with 2,4- Dichloroaniline as the Coupling Agent

Sadiya Ahmed Dhahir


Simple, rapid and sensitive spectrophotometric method was proposed for the analysis of thymol in pure form as well as in pharmaceutical tablets. The method is based on the diazotization reaction of 2,4-dichloroaniline with sodium nitrite in hydrochloric acid medium to form diazonium salt, which is coupled with thymol in sodium hydroxide medium to form azo dye, showing absorption maxima at 419 nm. Beer’s law is obeyed in the concentration range of 1-10 µg mL-1 of thymol. The molar absorptivity is 2.3 × 104 L mol-1 cm-1 The method was successfully applied to the determination of thymol in pharmaceutical without any interference from common excipients used as additives in tablets. The results agree favorably with standard method

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