A new Schiff's base ligand immobilized agarose membrane optical sensor for selective monitoring of mercury ion

Abstract

A highly selective optical sensor was developed for the Hg2+ determination by chemical immobilization of 2-[(2-sulfanylphenyl)ethanimidoyl]phenol (L), on an agarose membrane. Spectrophotometric studies of complex formation between the Schiff's base ligand L and Hg2+, Sr2+, Mn2+, Cu2+, Al3+, Cd2+, Zn2+, Co2+ and Ag+ metal ions in methanol solution indicated a substantially larger stability constant for the mercury ion complex. Consequently, the Schiff's base L was used as an appropriate ionophore for the preparation of a selective Hg2+ optical sensor, by its immobilization on a transparent agarose film. A distinct color change, from yellow to green-blue, was observed by contacting the sensing membrane with Hg2+ ions at pH 4.5. The effects of pH, ionophore concentration, ionic strength and reaction time on the immobilization of L were studied. A linear relationship was observed between the membrane absorbance at 650nm and Hg2+ concentrations in a range from 1×10−2 to 1×10−5molL−1 with a detection limit (3σ) of 1×10−6molL−1. No significant interference from 100 times concentrations of a number of potentially interfering ions was detected for the mercury ion determination. The optical sensor was successfully applied to the determination of mercury in amalgam alloy and spiked water samples.