Electrochemical Detection of Pyrroloquinoline Quinone Coupled with Its Catalytic Function by Liquid Chromatography.

Coenzyme pyrroloquinoline quinone (PQQ) was electrochemically detected with high sensitivity and high selectivity by employing its redox catalytic function in reversed-phase high-performance liquid chromatography. This catalytic reaction involves oxidative decarboxylation of glycine by PQQ and the reoxidation of the reduced PQQ by Fe(CN)63- to accumulate Fe(CN)64-, of which the electrochemical detection allows amplified detection of PQQ. Increase by two orders of magnitude of the current was achieved as compared with a direct reductive detection, at a reaction time of 3min and a reaction temperature of 25°C. The detection limit was 0.2pmol (10-8M, 20μl). The present method was applied to quantification of PQQ in table vinegar, milk, and swine serum.