Microchip metal complex speciation: The nickel–bathophenanthroline disulfonic acid system

This is the first reported metal complex speciation of a single metal–ligand system by microchip electrophoresis. The nickel(II)–bathophenanthroline disulfonic acid system consists of three complexes with different stoichiometries, i.e., Ni(BPS)1, Ni(BPS)2 and Ni(BPS)3. These nickel complexes are readily separated by capillary electrophoresis at 30 kV, in 20 mM sodium tetraborate at pH 9.3, 214 nm UV detection. The identity of each Ni(II) complex species was confirmed by CE-ESI-MS. The three metal–complex species, in addition to the free ligand can be successfully separated on a 25 mm quartz microchip with associated UV detection. Optimal electrophoretic parameters for efficient speciation of the nickel bathophenanthroline disulphonic acid complexes were: injection 1.0 kV for 10 s, separation 1.4 kV for 13 s in 10 mM sodium tetraborate at pH 8.0, 214 nm linear imaging UV detection. The influence of electrokinetic injection on the efficiency of metal speciation was also investigated.