| Popis: |
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 10−1 m KI to I11− at 5 × 10−4 m KI. |
