engleski

Voltammetric determination of copper complexing capacity in water samples from Boka Kotorska Bay

Copper complexing capacity (CuCC) is ability of organic compounds to complex Cu2+ by forming inert complexes. Free (hydrated) Cu2+ and labile Cu2+ complexes are more bioavailable and thus more toxic than copper inert complexes. Voltammetric determination of CuCC includes titration of water sample at natural and acidic pH (pH 2) with Cu2+ standard solution. Cu from free/labile Cu species is measured by differential pulse anodic stripping voltammetry (DPASV). By the titration at acidic pH the sensitivity of the method is calculated. CuCC is usually expressed as organic ligand concentration (cL) with apparent stability constant (Kapp). cL and Kapp are calculated according to the Ružić-van den Berg linearization model. The electrochemical process of Cu in deeper seawater layers from Boka Kotorska Bay was different than in surface freshwater layers due to the stabilization of CuCl2- species in higher chloride ion concentration in the electrode double layer. An one-electron process was in seawater observed: Cu0(Hg) → Cu+ + e-. Oppositely, in freshwater samples a two-electron process was observed: Cu0(Hg) → Cu2+ + 2e-. CuCC of Boka Kotorska Bay water samples from three sampling stations are extremely influenced by hydrographic characteristics of the bay. CuCC results in April were generally higher than in July and it could be concluded that more organic ligands were present in April, probable as a consequence of a spring biological production induced by freshwater input of nutrients.

copper; pomplexation; seawater; freshwater; Boka Kotorska Bay

nije evidentirano