Polarographic investigation of the zinc-N,N-dihydroxyethylglycine system

Complex formation of zinc with N,N-dihydroxyethylglycine (Bicine) has been studied polarographically at various pH values. The electrode processes were found to be irreversible, the degree of which depending on pH of the solution. At pH 5 the system was evaluated as quasi-reversible. Zinc formed 1:1 and 1:2 simple metal-ligand complexes. At higher pH values in alkaline range, mixed hydroxy complexes were found to form. The following complex species MX1, MX2, M(OH)X, M(OH)X2 and M(OH)2X were evaluated. The logarithmic values of overall stability constants were 7.27, 8.50, 11.52, 12.66 and 15.85 respectively.