Capping the hydroxyl groups (-OH) of α-cellulose to reduce Hy-groscopicity for accurate 18O/16O measurement by EA/Py/IRMS

Qiulin Yan; Yu Zhao; Ran Ma; Bo Wang; Zhenyu Zhu; Ting Li; Ding He; Charles H Hocart; Youping Zhou

doi:10.1016/j.talanta.2023.124698

Capping the hydroxyl groups (-OH) of α-cellulose to reduce Hy-groscopicity for accurate ¹⁸O/¹⁶O measurement by EA/Py/IRMS

Talanta. 2023 Sep 1:262:124698. doi: 10.1016/j.talanta.2023.124698. Epub 2023 May 22.

Authors

Qiulin Yan¹, Yu Zhao¹, Ran Ma¹, Bo Wang¹, Zhenyu Zhu¹, Ting Li², Ding He³, Charles H Hocart⁴, Youping Zhou⁵

Affiliations

¹ Isotopomics in Chemical Biology (ICB), School of Chemistry and Chemical Engineering, Shaanxi University of Science and Technology, Xi'an, 710021, China.
² College of Science and Engineering, ARC Centre of Excellence for Australian Biodiversity and Heritage, Centre for Tropical Environmental and Sustainability Science, James Cook University, Cairns, 4878, Australia.
³ Department of Ocean Science and Center for Ocean Research in Hong Kong and Macau, The Hong Kong University of Science and Technology, Hong Kong SAR, China; State Key Laboratory of Marine Pollution, Hong Kong, China.
⁴ Isotopomics in Chemical Biology (ICB), School of Chemistry and Chemical Engineering, Shaanxi University of Science and Technology, Xi'an, 710021, China; Research School of Biology, Australian National University, Acton, 2601, ACT, Australia.
⁵ Isotopomics in Chemical Biology (ICB), School of Chemistry and Chemical Engineering, Shaanxi University of Science and Technology, Xi'an, 710021, China; Isotopomics in Chemical & Biological Oceanography (ICBO), Department of Ocean Science and Engineering, Southern University of Science and Technology, Shenzhen, 518055, China. Electronic address: zhouyp@sustech.edu.cn.

PMID: 37244243
DOI: 10.1016/j.talanta.2023.124698

Abstract

Obtaining an accurate measurement of ¹⁸O/¹⁶O at natural abundance level for land plants-derived α-cellulose with the currently popular EA/Py/IRMS (elemental analysis/pyrolysis/isotope ratio mass spectrometry) method is a challenge due to the hygroscopic nature of the exposed hydroxyl groups, as the ¹⁸O/¹⁶O of adsorbed moisture is usually different from that of the α-cellulose and the relative amount of adsorbed moisture is sample- and relative humidity-dependent. To minimize the hygroscopicity-related measurement error, we capped the hydroxyl groups of α-cellulose by benzylation to various degrees and found that the ¹⁸O/¹⁶O ratio of α-cellulose increased with the degree of benzyl substitution (DS), consistent with the theoretical prediction that a reduced presence of exposed hydroxyl groups should lead to a more accurate (and therefore more reliable) α-cellulose ¹⁸O/¹⁶O measurement. We propose the establishment of a moisture adsorption-degree of substitution or percentage of oxygen-¹⁸O/¹⁶O ratio equation, based on the measurement of C%, O% and δ¹⁸O of variably capped α-cellulose, so that a robust correction can be made in a plant species- and laboratory conditions-specific manner. Failure to do so will lead to an average underestimate of α-cellulose δ¹⁸O by 3.5 mUr under "average" laboratory conditions.

Keywords: Benzylation; EA/Py/IRMS; Hygroscopicity; Natural abundance (18)O/(16)O measurement; α-cellulose.