Dissociation constants for the zinc(II)-8-hydroxyquinoline complexes in aqueous and sodium dodecyl sulfate micellar solutions

The constants of dissociation of 8-hydroxyquinoline (pK(1) and pK(2)) and of its complexation with zinc ions (log beta(1), log beta(2)) in sodium nitrate aqueous solutions at 293 K were calculated by modeling potentiometric titration data. The values of log beta were obtained under conditions such that the complexes occurred simultaneously in the solution and at optimum values of the ionic strength and the ratio between the metal and ligand concentrations. The apparent constants of dissociation of 8-hydroxyquinoline and of its complexation with zinc ions in a 0.01 M sodium dodecyl sulfate solution were calculated. An increase in pK and log beta was explained by the stabilization of the different forms of the ligand and its complexes in the surfactant micellar phase.