LC Simultaneous Determination of Thioctic Acid, Benfotiamine and Cyanocobalamin in Thiotacid Compound Capsules

A simple, selective, sensitive, precise, simultaneous liquid chromatographic analysis of capsules containing thioctic acid, benfotiamine and cyanocobalamin was described. Good chromatographic separation was achieved using a Zorbax C18 (4.6 cm x 250 mm, 5 mu m) and a mobile phase consisting of acetonitrile-phosphate buffer pH 3.5 (15:85, v/v) at a flow rate of 0.9 mL min(-1). The ultraviolet detector was set a wavelength of 280 nm. Thioctic acid, benfotiamine and cyanocobalamin were eluted at 2.869, 3.752 and 13.689 min, respectively. The linear ranges for thioctic acid, benfotiamine and cyanocobalamin were 30-180, 4-24 and 0.025-0.150 mu g mL(-1), respectively. The recoveries of thioctic acid, benfotiamine and cyanocobalamine in pharmaceutical preparation were all greater than 98% and their relative standard deviations were less than 2.0%. The limits of detection were 2.57, 0.19 and 0.003 mu g mL(-1) for thioctic acid, benfotiamine and cyanocobalamin, respectively.