HPLC Analysis of Pyrroloquinoline Quinone in Capsules

Pyrroloquinoline quinone disodium salt (PQQ) is important in functional foods. The method for PQQ analysis has mainly been applied to very small amounts of material. When PQQ is used in functional foods, it is necessary to confirm the exact quantities present in the capsules. However, the microanalysis method is complicated and unsuitable for process analysis. In addition, large quantities of oils, fats, and ascorbic acid exist with PQQ in functional foods. These oils and fats interfere with extraction, while ascorbic acid reduces PQQ. Therefore, we have developed an HPLC analysis method for PQQ in soft capsules containing larger quantities of oil (19-fold) and ascorbic acid (5-fold). The influence of oils and fats was removed by washing with ethyl acetate and subsequent basic extraction, while ascorbic acid was removed by oxidation with air. This extraction method gave a good recovery. Furthermore, a standard-addition method was used to calculate the amount of PQQ in the capsules via a simple calculation.