Arginine as a ligand of cations: lead (II)

The behaviour of arginine as ligand was studied previously1,2, but the complex formation with lead (II) was not studied because it is very hard to investigate this system by employing the glass electrode. In this study the system lead(II) arginine was studied at 25°C by means of electromotive force measurements involving a lead amalgam electrode and at low lead (II) concentration to avoid precipitation. To maintain constant the activity coefficients, investigated solutions were prepared in constant ionic medium, i.e. 1.00 mol dm-3 NaClO4. Experimental data can be explained whitout assuming appreciable presence of polynuclear complexes in lead (II), while the presence of species with the participation of hydrogen ions must be considered. The species present with the relative equilibrium constants were found and calculated. It can be considered that arginine bonds lead (II) in the protonated form (HL). The behaviour is similar to that shown in the case of other cations1,2. 1. Clarke, E.R.; Martell, A.E. J.inorg. Nucl. Chem. 1970, 32, 911-926. 2. Antonilli, M.; Bottari, E.; Festa, M.R.; Gentile, L. Chem. Spec. Bioav. 2009, 21, 33-40.