Abstract: Anew potentiometric sensor for copper(Ⅱ) based on a titanium matrix is proposed. The sensor shows a Nernst response toward copper(Ⅱ) which seems to originate from the nonstoichiometric compound TiO_2-σ layer covering on the electrode surface according to the results of XPS spectra of the electrode surface and a.c. impedance of the electrochemical system. The sensor owned a linear range from 10^-5～10^-2 mol/L with a detection limit of 5×10^-6 mol/L in 0.1 mol/L citric acid-sodium dihydrogen citrate buffer solution of pH 2.2 The standard deviations determined by alternatively immersing the electrode in 1.0×10^-4 and 1.0×10^-3 mol/L levels six times are 1.7 mVand 1.4 mV, respectively. The e.m.f. drift in 10^-3 mol/L copper(Ⅱ) solution is less than 2mV within two hours. The sensor has an excellent selectivity for copper(Ⅱ) with respect to many common divalent cations.

Key words: Copper(Ⅱ), Potentiometry, Nonstoichiometric compound, TiO_2-σ