Development of a Spectrophotometric Method for Thiamazole Detection Using Alizarin Red S

This study presents a novel spectrophotometric method for the sensitive and selective detection of thiamazole (methimazole) using Alizarin Red S as a chromogenic reagent. The interaction between thiamazole and Alizarin Red S results in the formation of a stable ۱:۱ complex, characterized by a distinct increase in absorbance at ۵۲۰ nm and a visible color change from yellow-orange to reddish-purple. Under optimized conditions (pH ۷, ۳۵°C, ۱۵ min reaction time), the method demonstrates excellent linearity (R² = ۰.۹۹۸) over a concentration range of ۱-۸ µg/mL, with high precision and minimal interference from common pharmaceutical excipients. The method was successfully applied to quantify thiamazole in commercial tablet formulations, achieving recovery rates of ۹۸.۵-۱۰۱.۲% and relative standard deviations below ۱.۵%. This cost-effective, rapid, and instrument-friendly approach is well-suited for routine quality control and pharmaceutical analysis.

Keywords:

Thiamazole detection , Spectrophotometry , Alizarin Red S , Colorimetric method , Pharmaceutical analysis