Development of a highly sensitive and selective mercury optical sensor based on immobilization of bis(thiophenal)-4,4'-methylenedianiline on a PVC membrane.

A reversible optical sensor was fabricated for highly sensitive and selective determination of Hg(II) ions. The optode was prepared using a newly synthesized ionophore, bis(thiophenal)-4,4'-methylenedianiline, and ETH-5294 as a lipophilic H(+)-selective indicator in a plasticized PVC membrane. Different variables affect the optical signal such as pH and compositions of the membrane components were optimized. The spectrophotometric method (λmax 662 nm) was used for the determination of Hg(II). Under the optimum conditions, the optode has a wide linear dynamic range of 2.51×10(-13) to 1.02×10(-5) mol L(-1) Hg(II) with a detection limit as low as 3.43×10(-14) mol L(-1) and a response time of 90 s (for a highly diluted solution). The influence of potential interference ions on the Hg(II) determination was studied. The results showed that the prepared optical sensor was highly selective to Hg(II) ions so that it had no significant response to a wide variety of common metal ions. The response of the optode to Hg(II) is completely reversible and was lucratively applied for the determination of Hg(II) in different real samples.