High field NMR analysis of the degree of substitution in carboxymethyl cellulose sodium salt

An accurate high field (1H at 600.13 MHz) 1D and 2D study was performed on an aqueous solution of carboxymethyl cellulose (CMC) sodium salt at 90°C. A combination of 2D experiments was used, 1H¯1H totally correlated spectroscopy TOCSY, and reverse detected 1H¯13C hetero-correlated spectroscopy HMQC with gradient selection. This combination allows a full assignment of 13C NMR spectra. From the gated decoupled 13C 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