Ion-interaction chromatographic studies on metal ions complexed with Plasmocorinth B dye

The ion-interaction chromatographic behaviour of Plasmocorinth B (a disulphonated azo dye) and of its complexes formed with metal ions in oxidation states + 2 and + 3 (Cu2+, Ni2+, Al3+, Co3+, Fe3+, Ga3+) was investigated. The effect of cationic ion-pairing agents (tetramethyl-, benzyltrimethyl- and tetrabutylammonium) was also evaluated in the presence of alkali metal ions competitors (Li+ and Na+). The effects of organic modifier and of pH were also considered. The remarkably different behaviour of the ligand and the complexes suggests the formation of M(II)L- and M(III)L2(2-). The stoichiometry of complexes was confirmed by applying the electrostatic theory derived from Gouy-Chapman and a modified Langmuir adsorption isotherm to the experimental data.