Analytical complexation reactions of organic reagents with metal ions in a solidified gelatin gel

Solidified gelatin gel is an original medium for analytical complexation reactions between organic reagents and element ions. The chemical nature of this biopolymer enables the electrostatic immobilization of organic reagents bearing anionic groups, like Arsenazo III, by protonated amino groups of the macromolecule. It was shown that the exhaustive capacity of the matrix towards organic sulfonate reagents differing in the number of sulfonic groups and the geometrical size of molecules was related to the specific properties of matrices and the fractal properties of the gel surface. It was found that the conditions for the reactions of complex formation and decomposition of the reagents immobilized in the gel were identical to those for reactions in aqueous solutions. It was proved that the gel fixed on a transparent triacetylcellulose support could be used as a component of sensing elements of optical sensors and/or test systems. This was demonstrated by the examples of the determination of La(III), Th(IV), U(VI), Ca(II), and SO₄²⁻.