High field NMR analysis of the degree of substitution in carboxymethylcellulose sodium salt

An accurate high field (H-1 at 600.13 MHz) 1D and 2D study was performed on an aqueous solution of carboxymethyl cellulose (CMC) sodium salt at 90 degrees C. A combination of 2D experiments was used, H-1-H-1 totally correlated spectroscopy TOCSY, and reverse detected H-1-C-13 hetero-correlated spectroscopy HMQC with gradient selection. This combination allows a full assignment of C-13 NMR spectra. From the gated decoupled C-13 spectrum it is then possible to obtain not only the degree of substitution but also a good measure of the amount of esterification in each chemical position. Conductimetric titration supports the obtained results.