A New Method for the Analysis of the Substitution Pattern of Hydroxyethyl(methyl)-Celluloses Along the Polysaccharide Chain

Hydroxyethylmethyl celluloses (MSHE 0.15-0.26, DSMe 1.49-1.82) and hydroxyethyl celluloses (MSHE 1.89-3.03) are analyzed with respect to their substituent distribution in the polymer chains. The cellulose ethers are peralkylated and partially hydrolyzed, and are analyzed by electrospray ionization-ion trap-mass spectrometry (ESI-IT-MS). The randomness of the partial hydrolysis is proven. Quantitative evaluation of their mass spectra becomes possible after labeling the oligosaccharides at the reducing end. Reductive amination with o-aminobenzoic acid gives better results than hydrazone formation with cationic Girard's T reagent. Syringe pump infusion gives more-accurate results compared with liquid chromatography (LC)-ESI-MS. Profiles of the substituent distribution in the oligosaccharide fractions of DP 2-DP 7 are compared with the theoretical random distribution of glucosyl units in the chain.