As constantes de estabilidade dos complexos de íons tálio(I) e cádmio(II) com dipeptídeos de glicil-L-fenilalanina e L-fenilalanilglicina foram determinadas em solução aquosa a 25 °C e meio iônico 0,1 mol dm -3 usando uma combinação de técnicas potenciométricas e espectrofotométricas. Perclorato de sódio foi usado para manter a força iônica. A composição dos complexos formados foi determinada e observou-se que tálio (I) The stability constants of the complexes of thallium(I) and cadmium(II) ions with dipeptides of glycyl-L-phenylalanine and L-phenylalanylglycine were determined in aqueous solution at 25 °C and 0.1 mol dm -3 ionic medium using a combination of potentiometric and spectrophotometric techniques. Sodium perchlorate was used to maintain the ionic strength. The composition of the formed complexes was determined and it was shown that thallium(I) and cadmium (

The protonation equilibria of glycyl-glycine and its complex formation with the cerium(IV) ion in aqueous solution were studied over a wide pH range (2 to 12) using a combination of potentiometric and spectrophotometric methods at constant temperature (25 °C) and different ionic strengths [(0.02, 0.05, 0.10, 0.15, 0.30, 0.50, 0.70, and 1.00) mol 3 dm À3 sodium perchlorate]. Least-squares regression calculations are consistent with the formation of the CeL 3þ and CeHL 4þ species for the studied system, where L À represents the deprotonated peptide. The species concentrations were plotted at different pH values and were discussed. The dependence of the protonation of the ligand and the stability constant of the complex species on ionic strength is described by a DebyeÀHuckel type equation, and finally the results have been compared with the values reported previously and interpreted.