Non-destructive and direct determination of the degree of substitution of carboxymethyl cellulose by HR-MAS 13C NMR spectroscopy

M. Ferro, F. Castiglione, W. Panzeri, R. Dispenza, L. Santini, H. J. Karlsson, P. P. de Wit, A. Mele*

*Corresponding author for this work

Research output: Contribution to journalArticleAcademicpeer-review


We report on the direct assessment of the degree of substitution (DS) of carboxymethyl cellulose (CMC) by High Resolution Magic Angle Spinning (HR-MAS) 13C NMR spectroscopy. The method is applied to industrial CMCs with low and high viscosity and nominal DS, purified and technical samples, and from cellulose linters or wood. The preparation of a set of purified CMC working standards with accurate DS values for the method validation is also described. The DS values determined via HR-MAS 13C NMR on the industrial samples are critically compared to the corresponding values achieved through the USP 37 〈281〉 method (ASH method) and the HPLC method, and the advantages and limitations of the HR-MAS NMR method highlighted. Finally, the HR-MAS NMR approach allowed the accurate DS assessment in CMC with low DS, characterized by a non-negligible fraction of non-functionalized cellulose. The proposed “effective DS” accounts for the DS of the solvent-exposed CMC.

Original languageEnglish
Pages (from-to)16-22
Number of pages7
JournalCarbohydrate Polymers
Publication statusPublished - 1 Aug 2017
Externally publishedYes

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