Thermodynamic parameters for the formation of glycine complexes with magnesium(II), calcium(II), lead(II), manganese(II), cobalt(II), nickel(II), zinc(II) and cadmium(II) at different temperatures and ionic strengths, with particular reference to natural fluid conditions

Protonation constants and Mg2+, Ca2+, Pb2+, Mn2+-, Co2+, Ni2+, Cu2+, Zn2+ and Cd2+glycine complex formation constants have been determined in different aqueous media at different temperatures. Salt effects are explained by a complex formation model which takes into account the formation of weak species. From the temperature dependence of the formation constants, thermodynamic parameters ΔHθ (and in some cases ΔCθp) have been obtained. A rigorous analysis of literature data, together with experimental findings, allows recommended formation parameters, in the ranges 0 ≤ Ie ≤ 1 mol l−1 (Ie is the effective ionic strength) and 5°C ≤ T ≤ 45°C, to be obtained. Because the proposed model can be used in any electrolyte mixture in the above I and T ranges, the speciation in seawater, and other natural fluids, can be simulated by appropriate computer programs. The validity of the present approach which takes into account the ionic strength dependence of formation constants, together with the concepts of effective ionic strength and complex formation model, is discussed.