title: Determination of the degree of substitution of sodium carboxymethylcellulose by potentiometric titration and use of the extended henderson-hasselbalch equation and the simplex method for the evaluation.
abstract: Determination of the degree of substitution, D.S., of purified sodium carboxymethylcellulose, CMC, by potentiometric titration has been studied. Different mathematical descriptions of the acid-base properties of polyelectrolytes were tested on the titration curve. It was found that the extended Henderson-Hasselbalch equation reproduced the measured data well. It was therefore used as a basis for evaluating D.S. by the simplex method. The influence of ionic strength, I, on the shape of the titration curve was investigated and the effect of I on the precision of the titrations was evaluated. The titrations showed a precision of +/- 0.004 D.S.-units and the results were in agreement with those obtained from a dry-ashing method, within +/- 0.02 D.S.-units. The whole method, including preparation of solutions and titration, showed a precision of +/- 0.01 D.S.-units.
authors.affiliation: Department of Analytical Chemistry, University of Uppsala, P.O.B. 531, S-751 21 Uppsala, Sweden.
authors.forename: I
authors.initials: I
authors.lastname: Aggeryd
authors.forename: A
authors.initials: A
authors.lastname: Olin