Vitamin C, also known as ascorbic acid or L-ascorbic acid, is an essential nutrient involved in the repair of tissues and the enzymatic production of certain neurotransmitters. It is required for the functioning of several enzymes and immune performance, and is also an important antioxidant. This nutrient is found in many foods and is often used as a dietary supplement.

USP general chapter <580> describes a titration technique to determine the assay of Vitamin C as ascorbic acid, sodium ascorbate, and calcium ascorbate dehydrate, or their mixture in finished dosage forms as capsules, tablets, and oral suspensions.

This Application Note demonstrates the Vitamin C determination in water-soluble vitamin tablets. The methodology can also be applied for oil-soluble vitamin or mineral tablets, as well as oil- and water-soluble vitamin or mineral capsules.

The analysis demonstrates acceptable and reproducible results and well-defined titration curves. For the tested water-soluble vitamin tablet, a vitamin C content of 97.7% (n = 6, SD(rel) = 0.23%) is obtained, which is within the given USP criteria of 90–150%. An example titration curve is displayed in Figure 2.

After sample preparation, the determination of vitamin C in vitamin capsules or tablets can efficiently be carried out by using a Metrohm autotitrator. Fast and precise determination according to USP <580> is possible.