Complexation mechanism of dextrin with metal hydroxides

The complexation of dextrin with metal hydroxides was studied quantitatively by FT-IR and UV–visible reflectance techniques. Though three hydroxyl groups are present in
dextrin molecule, complexation involving only two hydroxyl
groups situated at the C-2 and C-3 positions has been studied by many investigators. Involvement of a third hydroxyl group at the C-6 position was examined in the present study. Since metal hydroxy sites were found to play a key role in the complexation precipitates of Ca(OH)2 and Pb(OH)2 were separately mixed with dextrin solutions at different ratios. Complexes with a stoichiometry of 2:3 (dextrin:metal ion) were identified, indicating the involvement of a third hydroxyl group. However, the ratio of metal ions to hydroxyl groups of dextrin remained as 1:2. Complexation between dextrin and metal hydroxide via complexation mechanism is proposed.