Optoelectrochemical sensor for lead based on electrochemically-assisted solvent extraction

Description/Abstract

A thin film containing the complexing agent 2-(5-bromo-2-pyridylazo)-5-(diethylamino)-phenol deposited on the surface of an ITO electrode has been used as a colorimetric sensor for lead. The sensor is based on a new electrochemically assisted solvent extraction method. When an anodic potential was applied to the thin-film sensing layer, lead ions were extracted from aqueous solution into the film resulting in an increase of absorbance at 550 nm. The magnitude of the absorbance change was linearly dependent on the concentration of lead in the range 0-5 ppm with an estimated limit of detection for a simple spectrophotometric method better than 250 ppb. The sensor was reset for a fresh measurement by applying a cathodic potential. The prospects for using this electroassisted extraction method in conjunction with optical waveguide evanescent field detection as a new integrated sensor for trace analysis are discussed.