Reactions of the synthesis of azo dyes in solidified gelatin gel and their analytical application in the determination of nitrites

Abstract

The interaction of aromatic sulfonates of azo and diazo components in diazotization and azocoupling reactions electrostatically immobilized on gelatin solidified gel was studied. It was found that, among the variety of the functional groups of the polymer (amino, hydroxy, and carboxy groups and guanidine, phenol, and sulfur-containing amino acid residues), some groups are capable of protonation and are responsible for the efficient electrostatic immobilization of aromatic sulfonates with amino and hydroxy groups. A sufficiently high capacity of the polymer gel causes the formation of a relatively large amount of immobilized compounds, which makes it possible to conduct different types of synthetic analytical reactions of the formation of azo dyes in these gelatin gels in the real-time mode. It was demonstrated that, in all cases, the rate-determining step is external diffusion. These effects were used for the preparation of irreversible sensing elements suitable for measurements of calibration functions using the fixed-time technique or the tangent method in the determination of nitrites in solutions.