Polarographic studies on simple and mixed ligand systems involving cephalosporins

Differential pulse polarography and cyclic voltammetry have been chosen to follow up the metal-drug interactions at low concentrations in unbuffered s olutions. Cephapirin, cefoperazone and cefuroxime form stable coordination compounds with Zn(ll) and Pb(ll) ions. The stoichiometric ratios of cephapi rin versus Zn(ll) or Pb(ll) ions in these compounds are 1:1, 1:2 and 1:3, r espectively. Cefoperazone gives one weak complex of molar ratio 1:1 with Zn (II) ions, but it reacts with Pb(II) ions forming two types of stable compl exes of ratios 1:1 and 1:2. One complex 1:1 species occurs between cefuroxi me and Pb(ll) but three complexes were appeared with Zn(ll) ions. The formation constants of the metal ions with a mixture of cephalosporin a nd glycine ligands are determined. The obtained mixed ligand complexes with molar ratios of 1:1:1 [metal :gly :cephal] are observed for the all system s, except, cefuroxime no appears this stoichiometry with Zn(ll) ions, it ga ve 1:1:2 complex directly. The formation of 2:1:1 complexes did not occurre d for the all studied cephalosporins.