Development of a mercury ion-selective optical sensor based on fluorescence quenching of 5,10,15,20-tetraphenylporphyrin Original Research Article

A selective optical chemical sensor for mercury ion based on a lipophilized sensing material (5,10,15,20-tetraphenylporphyrin, H2tpp) dissolved in a plasticized poly(vinyl chloride) (PVC) membrane has been developed. H2tpp immobilized in the PVC membrane acts not only as a selective host molecule for Hg2+, but also as a fluorescing transducer. The sensing mechanism involves the extraction of Hg2+ from aqueous sample solution to organic membrane phase and the formation of a metalloporphyrin complex between H2tpp and Hg2+, which results in the fluorescence quenching of H2tpp. The optode membrane containing H2tpp reversibly responds to Hg2+ and shows extremely high selectivity to Li+, Na+, K+, Mg2+, Cd2+, Cu2+, Fe3+, Ag+ and Pb2+. The detection limit for Hg2+ is 4.0×10−8 mol/l at pH 8.0. The response characteristics of the sensor including dynamic range, reversibility, reproducibility, response time and lifetime are discussed in detail. This sensor has been used for the determination of mercury ion in water samples containing potential interferents with satisfactory recovery.