Polarographic behaviour of pyridoxal 5′-phosphate

Abstract

The polarographic reduction of pyridoxal 5′-phosphate in several NN-dimethylformamide–water mixtures has been investigated. It has been found that one, two, or three waves appear depending on the experimental conditions. The dependence of their half-wave potentials and the variation of their intensities with pH for each solvent were studied. The rate of interconversion between the free and hydrated form of the carbonyl group is very fast. Indirect evidence for rapid intramolecular proton transfer was obtained. Tetramethylammonium cation and NN-dimethylformamide have a large influence on the relative intensities of the first wave. This can be explained by the formation of a complex between those species and the radical formed in the environment of the dropping mercury electrode.