Research Article

Studies on Synthetic and Natural Melanin and Its Affinity for Fe(III) Ion

Table 3

Equilibrium constants for the interactions of natural melanin-Fe(III)*.

Equilibrium (SD)

Fe(Ac)]2+/[Fe3+][Ac]5.20 (0.20)
Fe(Qi)2+]/[Fe3+][Qi]5.73 (0.22)
Fe(OH)(Cat)][H+]/[Fe3+][Cat2−]23.53 (0.18)
Fe(OH)(Cat)(Qi)]/[Fe(OH)(Cat)][Qi]5.66 (0.15)
Fe(OH)2(Cat)(Qi)2−][H+]/[Fe(OH)(Cat)(Qi)]−8.89 (0.05)
][H+]/[Fe(OH)(Cat)][Cat2−]4.1 (0.08)

*Obtained by fitting the average of three or more titrations.