Photoelectrochemical determination of inorganic mercury in aqueous solutions

An analytical method using an optical probe in a photoelectrochemical cell for the sensitive and selective determination of aqueous Hg2+ is presented. A previously synthesized Hg2+ selective chemosensor, proven to be Hg2+ sensitive up to 2 μg L−1, has been immobilized onto indium tin oxide (ITO) electrodes in a composite form with polyaniline. The coated ITO electrode was placed in a photoelectrochemical cell under closed circuit conditions in which the optical recognition of the chemosensor was converted to a measurable signal. A composite of the fluorescent chemosensor, Rhodamine 6G derivative (RS), and polyaniline (PANI) was immobilized on ITO glass plates and subjected to photovoltage measurements in the absence and presence of Hg2+. The optical responses of the coated electrode were used to determine the sensitivity and selectivity of the immobilized sensor to Hg2+ in the presence of background ions. The optical response of the PANI-dye coated electrode increased linearly with increasing Hg2+ concentration in the range 10–150 μg L−1, with a detection limit of 6 μg L−1.