New absorption-based optode for the detection of Hg(II) in water

The current paper describes a novel absorption-based optode for mercury (II) detection. The dye 2-(5-amino-3,4-dicyano-2H-pyrrol-2-ylidene)-1, 1,2-tricyanoethanide (L') is a specific ligand for Hg2+ in water, undergoing a colour change from violet to blue on the formation of the corresponding monochelated complex HgL. The dye L' was fixed on different supports by means of anionic exchange. Controlled pore glasses, cross-linked styrene and cellulose paper were used as supports and two different optode configurations were developed in order to couple them to the optical fibres. Photodegradation and leakage of the dye were thoroughly investigated by means of an accurate spectrophotometric analysis in the presence of mercury acetate [Hg(AcO)(2)] solutions. In order to reduce the photodegradation of the dye, an optoelectronic unit was developed using light-emitting diodes as sources and a suitable electronic circuit as the detecting system.