Boron doped diamond electrode modified with iridium oxide for amperometic detection of ultra trace amounts of arsenic(iii)

Abstract

Boron doped diamond (BDD) electrodes modified by electrodeposition from hydrous iridium oxide (IrOx) have been developed for the detection of arsenic(III). Potential cycling is used to deposit films of hydrous iridium oxide onto boron doped diamond electrode from a saturated solution of alkaline iridium(III) solution. A stable reversible redox couple was observed at the surface of modified electrode in both acidic and basic solutions. The properties of iridium oxide films, stability and its electrochemical properties were investigated by atomic force microscopy (AFM) and cyclic voltammetry. The modified electrodes showed excellent electrocatalytic activity toward oxidation arsenic(III) over a wide pH range (2–8); also they showed an excellent analytical performance for the amperometric detection of arsenic(III). The detection limit, sensitivity, response time and linearity are 2 nM, 4.2 nA nM⁻¹, 60 ms and 20 nM–50 µM. The precision for 10 replicate determinations of 40 µM arsenic was 0.80% (RSD). These analytical parameters compare favourably with those obtained with modern analytical techniques such as inductively coupled plasma mass spectrometry and hydride generation atomic fluorescence spectrometry. The advantageous properties of this modified electrode for arsenic determination are its inherent stability, excellent catalytic activity over a wide pH range, high sensitivity and simplicity.