Simultaneous determination of molar degree of substitution and its distribution fraction, degree of acetylation in hydroxypropyl chitosan by 1H NMR spectroscopy

Pengbo Wang; Xingshuang Lv; Bingqian Zhang; Tengbin Wang; Chenbo Wang; Jiaxi Sun; Kun Zhang; Ya'nan Wu; Jian Zhao; Yongqin Zhang

doi:10.1016/j.carbpol.2021.117950

Simultaneous determination of molar degree of substitution and its distribution fraction, degree of acetylation in hydroxypropyl chitosan by ¹H NMR spectroscopy

Carbohydr Polym. 2021 Jul 1:263:117950. doi: 10.1016/j.carbpol.2021.117950. Epub 2021 Mar 24.

Authors

Pengbo Wang¹, Xingshuang Lv¹, Bingqian Zhang², Tengbin Wang¹, Chenbo Wang¹, Jiaxi Sun³, Kun Zhang¹, Ya'nan Wu¹, Jian Zhao⁴, Yongqin Zhang⁵

Affiliations

¹ State Key Laboratory Base of Eco-chemical Engineering, College of Chemical Engineering, Qingdao University of Science and Technology, No.53 Zhengzhou Road, Qingdao, 266042, China.
² Qingdao Institute of Bioenergy and Bioprocess Technology, Chinese Academy of Sciences, No.189 Songling Road, Laoshan District, Qingdao, 266101, China.
³ Key Laboratory of Marine Drugs, Ministry of Education, Shandong Provincial Key Laboratory of Glycoscience and Glycoengineering School of Medicine and Pharmacy, Ocean University of China, No.5 Yushan Road, Qingdao, 266003, China.
⁴ State Key Laboratory Base of Eco-chemical Engineering, College of Chemical Engineering, Qingdao University of Science and Technology, No.53 Zhengzhou Road, Qingdao, 266042, China; Key Laboratory of Rubber-Plastics Ministry of Education/Shandong Provincial Key Laboratory of Rubber-Plastics, Qingdao University of Science & Technology, No. 53 Zhengzhou Road, Qingdao, 266042, China. Electronic address: zhaojian@qust.edu.cn.
⁵ State Key Laboratory Base of Eco-chemical Engineering, College of Chemical Engineering, Qingdao University of Science and Technology, No.53 Zhengzhou Road, Qingdao, 266042, China. Electronic address: zyq0205@qust.edu.cn.

PMID: 33858567
DOI: 10.1016/j.carbpol.2021.117950

Abstract

Under the assistance of ¹³C NMR and ¹H-¹³C HSQC, we develop a novel ¹H NMR assay for the substitution sites and degrees in hydroxypropyl chitosan (HPCS) by optimizing sample preparation and measurement method. We find that the chemical shift of HOD peak increases linearly with the increase of DCl concentration but declines with the rise of measurement temperature. According to the regression line, the HOD peak could be moved to a desired position of non-interference with other peaks by changing DCl concentration. Other DCl-responsive peaks are found and elucidated. Accordingly, the substitution fraction (NH₂-substitution and OH-substitution) and the degree of acetylation are well discriminated and determined. The total molar degree of substitution (MS) obtained is basically consistent with those of elemental analysis and the existing NMR methods. This structural analysis is extendable to other amino-containing saccharides. The ¹H NMR method could be used widely in acid-soluble polysaccharides and their derivatives.

Keywords: Analysis; Chitosan; Hydroxypropyl; NMR; Substitution.

MeSH terms

Acetylation
Chemistry Techniques, Analytical / methods*
Chitosan / analogs & derivatives
Chitosan / analysis*
Chitosan / chemistry*
Proton Magnetic Resonance Spectroscopy / methods*
Temperature
Water / chemistry

Substances

Water
Chitosan