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The model ligand 1-(2-pyridylazo)-2-naphthol (PAN) has two pK_a values of 2.5 and 11.2 corresponding to the pyridinium ion, and the phenolic group, respectively. The related chelating agent, 2-(5′-bromo-2′-pyridylazo)-5-diethyl aminophenol (PADAP), has pK_a values of 1.0, 3.0 and 11.2 corresponding to the 3-bromopyridinium ion, the N,N-diethyl-anilinium ion and the phenolic group, respectively. On chelation of PADAP with Cd(II), Cu(II), Ni(II), Zn(II) and Pb(II) a 1:1 stoichiometry is found in the intermediate pH range 4–9, indicative of square planar or tetrahedral complexes. Co(II) forms a particularly stable chelate with a 1:2 stoichiometry over the pH range 0–14 with the other chelates showing greater lability when investigated by UV-visible spectrophotometry. Adsorptive stripping voltammetry (AdSV) is compared to capillary zone electrophoresis (CZE) for the detection and determination of trace …