Development and evaluation of methods for determining title pattern of functionalization in sodium carboxymethylcelluloses

Sodium carboxymethylcellulose (NaCMC) with varying degrees of substitution (DS) was investigated with different analytical methods in order to charact erize the functional group distribution. The following methods were tested and adapted: high-resolution C-13 NMR spectroscopy in the solid state (C-13 CP/MAS NMR) and C-13 NMR spectroscopy on solutions of NaCMC samples with a reduced molar mass. Partial degradation was accomplished by ultrasonic mea ns and with the enzyme endoglucanase. Combining the two techniques resulted in the greatest reduction in molar mass and hence in the best spectral res olution. Analysis of the NaCMC fragments following ultrasonic and/or endogl ucanase degradation also reveals another interesting experimental finding. It appears that ultrasonic degradation is favored at unsubstituted areas ne ar the center of the chain. These methods were compared with the following already familiar techniques of analysis: titrimetric techniques; C-13 and H -1 NMR spectroscopy as well as HPLC on completely hydrolysed solutions (hyd rolysis with perchloric acid, trifluoroacetic acid and sulfuric acid). All of the methods characterize the samples as a series with increasing DS, the values of which range from 0.9 to 2.4. Methods that permit analysis of the partial degree of substitution produced the distribution x(2) > x(6) > x(3 ). Therefore, they are in principle suited for determining the functionaliz ation pattern of the NaCMC samples relative to one another. The most suitab le method can therefore be selected according to the objectives and the app aratus available. However, the measured values do exhibit considerable spre ad, variances of approx. 20%, thus, place restrictions on using the values of DS or x(i) in absolute comparisons beyond these methods.