RT Journal Article
T1 Disclosing an NMR-Invisible Fraction in Chitosan and PEGylated Copolymers and Its Role on the Determination of Degrees of Substitution
A1 Novoa Carballal, Ramón
A1 Riguera Vega, Ricardo
A1 Fernández Megía, Eduardo
K1 Chitosan
K1 Degree of substitution
K1 NMR-invisible fraction
K1 PEG
K1 Transverse relaxation time
AB An unexpected 1H NMR invisible fraction (IF) for chitosan (CS) and CS-g-PEG is reported. The presence of this IF is remarkable considering that solution NMR is recognized as the method of choice for studying structural modifications in CS, including the degrees of acetylation (DA) and substitution (DS). In spite of IF figures as high as 50%, this IF does not interfere in the correct determination of the DA by 1H NMR, pointing to a homogeneous distribution of acetyl groups along the visible and invisible fractions. Quite in contrast, the IF negatively biases the determination of the DS in CS-g-PEG, with relative errors as high as 150% in a broad range of temperatures, pH values, and concentrations. This fact raises concerns about the accuracy of previously reported DS data for CS-g-PEG and many other CS copolymers. Efficient user-friendly conditions have been developed for the correct determination of the DS of CS-g-PEG by depolymerization by nitrous acid
PB American Chemical Society
SN 1543-8384
YR 2013
FD 2013
LK http://hdl.handle.net/10347/16952
UL http://hdl.handle.net/10347/16952
LA eng
NO Novoa-Carballal, R., Riguera, R., & Fernandez-Megia, E. (2013). Disclosing an NMR-Invisible Fraction in Chitosan and PEGylated Copolymers and Its Role on the Determination of Degrees of Substitution. Molecular Pharmaceutics, 10(8), 3225-3231. doi: 10.1021/mp400267m
NO This work was financially supported by the Spanish Government (CTQ2009-10963, CTQ2012-34790, CTQ2009-14146-C02-02, and CTQ2012-33436) and the Xunta de Galicia (10CSA209021PR and CN2011/037)
DS Minerva
RD 4 may 2026