Periodate oxidation of sodium alginate in water and in ethanol–water mixture: a comparative study

Periodate oxidation of sodium alginate in aqueous solution as well as a dispersion in 1:1 ethanol–water was examined. The oxidation proceeded smoothly in both media, and the kinetics of oxidation was surprisingly similar. Polymer cleavage was observed in both media, but it was extensive in ethanol–water. The weight-average molar mass (Mw) of the oxidized product obtained from aqueous solution showed a gradual decrease with increase in the periodate concentration, whereas, except for very high periodate equivalent, the change in Mw was not reflected with increase in concentration of periodate in ethanol–water. The oxidized alginate obtained from the ethanol–water mixture was found to be more efficient in crosslinking proteins such as gelatin, leading to hydrogels. Oxidation of a dispersion has the advantage of generating large quantities of the oxidized alginate in higher yield with one reaction using less solvent.