Glutathione analysis and quantification in Korean supplements: method development and validation

In this study, a liquid chromatography-ultraviolet (LC-UV) detection method was established for the rapid and accurate analysis of reduced and oxidized glutathione in glutathione supplements without the need for derivatization. Method validation revealed a satisfactory linearity (R ² ≥ 0.999), accuracy (recovery: 92.18-102.85%), and precision (relative standard deviation ≤ 1.91%), with the limits of detection (for 100 g of product) being 0.26 and 0.15 g for reduced glutathione and oxidized glutathione, respectively. The developed method was applied to 60 glutathione supplements (25 films, 24 tablets, 6 granules, and 5 powders) distributed in Korea between May and September 2024. Significant variations in the glutathione content were observed across products and formulations, with discrepancies between the measured and labeled values in certain samples. The presented method holds great potential for quality control and label accuracy verification in glutathione supplements.