Electrochemical detection of trace amount of arsenic(III) at glassy carbon electrode modified with cobalt oxide nanoparticles

Novel cobalt oxide nanoparticles based sensor for the detection of trace amount of As3+ ion in aqueous solution has been developed. Cyclic voltammetry at potential range -1.1 to 1.1 V from aqueous buffer solution (pH 7) containing CoCl2 produced a well-defined cobalt oxide (CoOx) nanoparticles deposited on the surface of glassy carbon electrode. The resulting electrode surfaces and its morphology were examined with both cyclic voltammetry and scanning electron microscope (SEM) techniques. The modified electrode shows excellent catalytic activity toward arsenic oxidation at wide pH range, 5-11. The response to As3+ on the modified electrode was examined using cyclic voltammetry and hydrodynamic amperometry. The amperometric detection of arsenic is carried out at 0.75 V versus Ag/AgCl reference electrode in phosphate buffer solution with pH 7. The detection limit (S/N = 3) was 11 nM with linearity up to 4 orders of magnitude and sensitivity of 111.3 nA/mu M. The response time of the electrode to achieve 95% of the steady-state current is <2 s. No measurable reduction in analytical performance of the modified electrode was found by storing the electrode in ambient conditions for 30 days. This modified electrode recedes many advantageous such as remarkable catalytic activity, good reproducibility, simple preparation procedure and long-term stability of signal response during arsenic oxidation. In addition the interference effects of various reducing compounds for signal response of As(III) are negligible. The immobilization of cobalt oxide nanoparticles on the surface of GC electrode appears to be a highly efficient method for the development of a new class of sensitive, stable and reproducible As3+ electrochemical sensor. (c) 2007 Elsevier B.V. All rights reserved.