An accurate, precise, and simple spectrophotometric method is proposed for the determination of the antithyroid drug carbimazole using ruthenium(III) chloride. This method is based on the formation at room temperature of a stable yellow-colored complex with λmax 370 nm. The method has a Beer’s law range of to × 10 2 µg mL−1, molar absorptivity coefficient ε = × 103 L mol−1 cm−1, and correlation coefficient of . The metal:ligand (M:L) ratio of the complex was confirmed by the mole ratio and Job’s method of continuous variation, suggesting a 1:2 stoichiometry. |