Study of the Catalytic Polarographic Pre-Wave of Nickel(II) Induced by Cimettdine

We carried out a comprehensive study of the Ni(II) pre-wave induced by cimetidine in sodium veronal - nitric acid - sodium nitrate media using various polarographic techniques in order to establish the mechanism of the electrode process. This was found to involve the formation of catalytic complexes of the aquo-Ni(II) and veronal-Ni(II) ions with deprotonated cimetidine adsorbed on the electrode surface, which was followed by reduction of the Ni(II) in the complexes and the consequent release of the catalytic ligand. The pre-peak obtained by differential pulse polarography for the 5 l0−4M Ni(II) - 5 10−3M sodium veronal-HNO3-NaNO3 system (pH 8.5, ionic strength 0.4 M) can be exploited for the quantitative determination of cimetidine over the concentration range 1-10−6 -1 105 M.