**Abstract**

Vitamin C and glutathione are mostly found together in pharmaceutical products. These two components protect each other from oxidation by forming an antioxidant couple and mutually reinforcing each other's actions. This paper describes a method for determining the activity of the antioxidant couple in pharmaceutical products using HPLC/MS. An Agilent 6125 HPLC equipped with MSD and DAD detectors was used. The first detector is for the detection of glutathione, and the second is for the detection of ascorbic acid. The MS spectrum of glutathione (Glut) was dominated by the signal m / z + = 308.2, which corresponds to the Glut-H + cation. The MS spectrum of ascorbic acid (AA) was dominated by signals m/z + = 177 and 375, which corresponds to the cations AK-H + and 2AK-Na +. The use of HPLC with two detectors (MS and DAD) made it possible to simultaneously determine both components of the antioxidant couple in pharmaceutical products without derivatization and any preliminary sample preparation. The method meets the FDA criteria for accuracy, selectivity, robustness, and reproducibility, and has a low detection limit of both components of the antioxidant couple.

**Keywords:** *antioxidant* couple, glutathione, ascorbic acid; potency, HPLC/MS; Validation
