Thermodynamic study of interaction between some transition metal ions and L-Alanine

Using UV-vis spectrophotometic method, the formation constants for interaction of Cd2+(aq) andCo2+(aq) ions with L-Alanine were experimentally studied at pH = 4.1 ± 0.01 (50mM of potassiumhydrogen phthalate buffer), ionic strength of 0.1M potassium nitrate and at 5 differenttemperatures 15,20, 25,30 and 35°C. The optical absorption spectra of mixtures containingconsidered cations and L-Alanine were analyzed by using SQUAD software, in order to obtainthe formation constants and the stoichiometry of respect complexes. The best fitting of our resultsshowed that the 2:1 complex respect to each studied system (Cd2+(aq) + L-Alanine) and (Co2+(aq) +L-Alanine) is formed. Regarding the values of formation constants at different temperatures andusing Van't Hoff equation, enable us to calculate the respect thermodynamic functions offormation such as ΔH , ΔS , ΔG , … of studied complexes.