Paper electrophoretic determination of the stability constants of binary and ternary complexes of copper(II) and cobalt(II) with nitrilotriacetate and cysteine

A paper ionophoretic method is described for the study of equilibria in mixed ligand (nitrilotriacetate–cysteine) complex system in solution. The proportion of ionic species of nitrilotriacetate (NTA) and cysteine were varied by changing the pH of background electrolyte. The stability constants of Cu(II)–NTA–cysteine and Co(II)–NTA–cysteine complexes were found to be 6.35 ± 0.05 and 5.45 ± 0.02 (logarithm stability constant values), respectively, at ionic strength 0.1 M and a temperature of 35 °C.