The Azo Dyes Conjugated Onto Chitosan And Characterization

Synthetic pigments have been widely used in fields such as food、medicine and so on. As the major synthetic pigments, azo dyes are reduced to aromatic amines easily in human body. Aromatic amines are poisonous which led to cancer and inherited disease. More and more attention was paid on the damage of edible pigments with the increasing of food safety problems. It seemed to be more and more important to seek for safe and edible pigments by pigment modification.As the only alkaline and natural polysaccharide, chitosan could be good carrier of edible pigments for it was nontoxic polymer with good biocompatibility, and chitosan with high molecular weight was hard to degrade and adsorb in human body. We designed two ways to synthesis grafted chitosan by azo dyes in advantage of the amino group of chitosan:1 、 It mainly reacted through nucleophilic substitution by azo dyes with epichlorohydrin to get intermediate with epoxy group at the environment of weak alkaline. The C2-NH2 was prior to react with epoxy group in the environment of alkaline or neutral. The intermediate opened the epoxy group to get grafted chitosan by azo dyes;2、The azo dyes bearing phenolic hydroxyl group with chitosan and aldehyde could be involved in Mannich reaction in diluted acid of alcohol to synthesize grafted chitosan just by one step.Sunset yellow, lemon yellow, orange II, amaranth and carmine were used to synthetic grafted chitosan by the two ways. The reducibility of grafted chitosan and azo dyes was detected by NaHSO3 depending on ultraviolet absorption spectrum.