HIGH-PERFORMANCE LIGAND-EXCHANGE LIQUID-CHROMATOGRAPHY (HPLEC) OF AROMATIC-AMINES WITH COPPER(II), NICKEL(II) AND ZINC(II) LOADED CHELATING SILICA-GEL COLUMNS

An 8-hydroxyquinoline, 8-hydroxy-5-sulphonic-acid-quinoline and a 2-amino-1-cyclopentene-1-dithiocarboxylic acid silica gel, loaded with copper(II), nickel(II) or zinc(II) were examined for the separation of some aromatic amines in the normal phase mode. All phases studied interact strongly with the sample compounds, but the presence of cations increases the selectivity of the columns drastically in some cases. Nickel(II) or zinc(II) loading proved to be better than copper(II) loading, because with these ions strong peak broadening and disturbances of the baseline are avoided. Endcapping of the chelating silica gels was indispensable in order to obtain reasonable efficiencies.