Determination of Alpha-Lipoic Acid in a Nutritional Supplement Using High Performance Liquid Chromatography

Abstract

Alpha lipoic acid has the ability to react and neutralize reactive oxygen spe-cies (ROS) such as superoxide radicals, simple oxygen, hydroxyl radicals, hypochlorous acid and peroxyl radicals. A rapid high-performance liquid chromatographic method for determination of lipoic acid in a nutritional supplement was developed. The method involved sample preparation and the mobile phase comprised of 50 mM disodium hydrogen phosphate buffer (pH 2.5 adjusted with 1 M H3PO4): acetonitrile in the ratio of 50:50. The separa-tion was done using a C18 column (150 mm) and detection was carried out using UV detection at 201 nm. The assay was found to be linear in the range of 1.56 - 50 µg/mL with the correlation coefficient of 0.9997. Method preci-sion was determined while LOD was 0.05 μg/ mL and LOQ 0.15 μg/ mL. The chromatographic peak LA retention time was 6 min.