Highly selective optical sensor for mercury assay based on covalent immobilization of 4-hydroxy salophen on a triacetylcellulose membrane

A novel optical sensor based on covalent immobilization for mercury(II) assay has been described based on the immobilization of 4-hydroxy salophen on a triacetylcellulose membrane. 4-Hydroxy salophen is covalently bonded to a transparent triacetylcellulose film. The sensing membrane is in contact with Hg(II) ions at pH 6.0, and changes the color from white-yellow to orange (323–429 nm). The sensing membrane is capable of determining Hg(II) with an outstanding high selectivity over a dynamic range of 1.0 × 10−6 and 1.0 × 10−2 mol L−1 with a limit of detection of 1.3 × 10−7 mol L−1 (0.02 μg mL−1). The sensor shows a response time of 6 min and the membrane can be used for more than 6 months without observing any major deviation. The optode revealed very good selectivity with respect to many cations including alkali, alkaline earth, transition and heavy metal ions. The selectivity of optode to Hg(II) ions is good. The proposed optode was applied to the determination of Hg(II) in environmental water samples.