A polarographic study of the schiff bases of pyridoxal-5'-phosphate. Influence of the amine protonation equilibrium on the stability

Schiff bases obtained from reaction of pyridoxa1-5‘-phosphate with n-hexylamine, L-lysine. N-acetylethylenediamine and tris(hydroxymethyl)-aminomethane were studied by DC and DP polarography, as a function of the pH, the amine concentration arid the solution composition. I-t curves show that the electrochemical processes are diffusion—control led in the limiting current and the apparent constants of the formation equilibrium were determined. A relation between the stability maximum of the Schiff bases and the ionization constants of the amines was observed