DETERMINATION OF COPPER IN SEAWATER BY ANODIC-STRIPPING VOLTAMMETRY USING ETHYLENEDIAMINE

The complexing properlies of ethylenediamine (en) were Investigated as a means of performing the analysis of ligand-exchangeable and labile (i.e., directly reducible at pH 8) Cu in seawater at trace levels. Stripping Polarographic or pseudopolarographic determinations show that the Cu-en complex behaves reversibly In seawater, exchanging two electrons at the mercury drop electrode (HMDE). The role of chloride Ions in competitive reactions with en for copper during the stripping step was also studied. In seawater made 2 ✕ 10‒3 M in en, Cu(II) can be detected at the HMDE by differential pulse anodic stripping voltammetry (DPASV) at the 5 ✕ 10‒10 M level with a deposition time of 10 min. A new procedure for measuring pH 8 labile copper in seawater is obtained by coupling DPASV with a medium alteration method. Addition of en at the end of the electrolysis increases peak height by more than twice by doubling the current yield per mole of Cu and by removing interferences associated with the oxidation of Cu in Cl‒ media. This procedure facilitates the voltammetric study of Cu in seawater under natural conditions. © 1990, American Chemical Society. All rights reserved.