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摘要
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The degree of deacetylation (DDA) is an essential property of a chitosan sample and significantly impacts its applicability. Therefore, the analysis of chitosan's DDA is critical. We have successfully developed an analytical method for determining the chitosan sample's average DDA and DDA distribution using capillary zone electrophoresis (CZE). However, when the DDA distribution of the chitosan sample becomes broad, the difference in UV absorption coefficients between chitosan chains with different DDAs increases, leading to a negative deviation in the average DDA value measured by CZE. A chitosan sample with a broad DDA distribution could be obtained by mixing three chitosan samples with different average DDAs in a monomer molar ratio of 1:1:1. CZE analysis of the mixed chitosan sample revealed a broad UV absorption peak, leading to a deviation in the CZE measurement result from the average DDA value measured by NMR. To solve this problem, we prepared a series of chitosan samples with different average DDAs to establish a UV absorption-DDA calibration curve, correcting the measurement deviation caused by the varying UV absorption coefficients of chitosan chains with different DDAs, thus obtaining the accurate average DDA value and distribution for chitosan sample.
Furthermore, we deacetylated the mixed chitosan sample with broad DDA distribution to a high average DDA value (~95%). According to the previously established calibration curve of Log(DDA%) versus AA-amine, we can accurately acetylate the high DDA sample to prepare a chitosan sample with a specific average DDA and narrow DDA distribution. |