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 Hg(2+) is presented. A previously synthesized Hg(2+) selective chemosensor, proven to be Hg(2+) sensitive up to 2 microg 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 Hg(2+). The optical responses of the coated electrode were used to determine the sensitivity and selectivity of the immobilized sensor to Hg(2+) in the presence of background ions. The optical response of the PANI-dye coated electrode increased linearly with increasing Hg(2+) concentration in the range 10-150 microg L(-1), with a detection limit of 6 microg L(-1).