Kinetic Spectrofluorometric Determination of Thioctic Acid in Bulk and Pharmaceutical Preparations via its Oxidation with Cerium(IV)

A highly simple and sensitive kinetic spectrofluorometric method was developed for the determination of thioctic acid. The method is based on the oxidation of the studied drug with cerium(IV) ammonium sulfate in acidic medium. The fluorescence of the produced Ce(III) was measured at 365 nm after excitation at 255 nm. The different experimental parameters affecting the development and stability of the reaction product were carefully studied and optimized. The method is applicable over the concentration range of 0.02 to 0.12 μg/mL with a detection limit of 6.06 × 10^?3 μg/mL and a quantification limit of 0.02 μg/mL. The method was successfully applied for the assay of the studied drug in pharmaceutical formulations. The results obtained were in good agreement with those obtained with the reference method.