Solid-state and solution conformation of scleroglucan

A potentiometric-titration procedure, in which samples are always exposed to an excess of I₂-KI has been developed for measuring iodine-binding capacity of starches. Binding capacity of amylose under these conditions is ～30% as opposed to 20% by conventional potentiometric titration. Spectrophotometric absorbance is essentially the same for either method, but is proportional to potentiometric values only in the excess-iodine titration procedure. Effects of variation of concentration of I₂, KI, and phosphate buffer and of temperature on the reaction have been examined. Calculations based on concentration of reactants in solution indicate that the binding species varies from I₃^? at 10^?1m KI to I₁₁^? at 5 × 10^?4m KI.