Determination of stability constants of metal(II)-methylcysteine and metal(II)-nitrilotriacetate-methylcysteine complexes with using a paper electrophoretic method

A method involving the use of paper ionophoresis is described for the study of the equilibria in mixed ligand complex systems in solution. Present method is based on the movement of a spot of metal ion under the electric field with the complexants added in the background electrolyte at pH 8.5. The concentration of primary ligand nitrilotriacetate (NTA) was kept constant while that of the secondary ligand methylcysteine was varied. The plot of log [methylcysteine] versus mobility were used to obtain information on the formation of mixed complexes and to calculate its stability constants. The binary equilibria metal(II)-methylcysteine and metal(II)-NTA have also been studied, since this is a prerequisite for the investigation of mixed complexes. The stability constants of the complexes Pb(II)-NTA-methylcysteine and UO₂ (II)-NTA-methylcysteine were found to be 3.03 ± 0.05 and 3.42 ± 0.09 (log K values) at ionic strength 0.01 M and a temperature of 35°C. Original Russian Text ? B.B. Tewari, 2009, published in Zhurnal Neorganicheskoi Khimii, 2009, Vol. 54, No. 1, pp. 151–155.