Determination of stability constants of copper(II)-glycine complex in mixed solvents by copper(II)-selective electrode

The first stability constants (in log beta (1) form) of the Cu(II)-glycine complex have been determined at 25 degreesC and ionic strength of 0.10 mol/ L in water and in mixed aqueous solutions of methanol (MeOH), ethanol (EtOH ), dimethylsulfoxide (DMSO), N,N-dimethylformamide (DMF) and 1,4-dioxane (D OX) from pH and pCu measurements of cells containing a copper(II) ion-selec tive electrode. In general, the stability constants of the complex increase with increasing composition of the co-solvents in the order: DOX > DMF > D MSO > EtOH > MeOH > H2O. An approximate linear relationship between log bet a (1) and the mole fraction of the co-solvent was observed for the complex in all the mixed solvents except in DMF + H2O mixtures. The response of the ion selective electrode to copper(II) ion in the mixed solvents was also i nvestigated. The effects of solvent on the complex stability are discussed in terms of the polarity of the solvents.