Vapor pressure curve determination of α-lipoic acid raw material and capsules by dynamic thermogravimetric method

alpha-Lipoic acid (ALA) has been described as a potent biological antioxidant and detoxification agent. ALA has become a common ingredient in multivitamin formulas and anti-aging supplements. Vapor pressure determination by thermogravimetric method has been used to characterize drugs and pharmaceutical preparations. The aim of this study was to determinate the vapor pressure of ALA raw materials and capsules using thermogravimetric method. TG curves of ALA were determined by the TA Instruments model SDT Q600 TG/DSC Thermal Analyzer. The TG curves of ALA displayed a single mass loss in the temperature range (from 227.16 to 319.29 degrees C), at a heating rate of 10.0 degrees C min(-1). ALA showed zero order kinetic reaction for all heating rates (10.0, 20.0, 40.0, 60.0 and 80.0 degrees C min(-1)). The vapor pressure curves were constructed from the Langmuir equation. This work suggests that thermogravimetry can be utilized as a rapid and effective technique for the estimating of ALA vaporization characteristics. (c) 2012 Elsevier B.V. All rights reserved.