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The fluorescence spectra and response characteristics of two porphyrin compounds meso-tetrakis(2-hydroxynaphthyl) porphyrin and meso-tetra (2-thiophene) porphyrin (MTHNP) to Hg(2+) were investigated. MTHNP showed preferable fluorescence response to Hg(2+). Thereby, an efficient and selective fluorimetric optode membrane based on the fluorescence quenching of MTHNP for Hg(2+) ion determination at low concentration levels has been developed. The sensing membrane containing MTHNP reversibly responded to Hg(2+) with a working concentration range covering from 5.0×10(-9) to 1.25×10(-5)M with a relatively fast response time less than 3min. In addition to high stability, reversibility and reproducibility, the sensor showed extremely high selectivity toward Hg(2+) ion with respect to some alkali, alkaline earth and heavy metal ions. The limit of detection for Hg(2+) was 5.0×10(-9)M. The proposed fluorescent sensor was successfully applied to the direct determination of mercury content of biofenac eye drop, hair and different water samples., (Copyright © 2014 Elsevier B.V. All rights reserved.)