Isotopomics in Chemical Biology (ICB), School of Chemistry and Chemical Engineering, Shaanxi University of Science and Technology, Xi'an, 710021, China.
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.
Talanta. 2023 Sep 1;262:124698. doi: 10.1016/j.talanta.2023.124698. Epub 2023 May 22.
Obtaining an accurate measurement of O/O 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 O/O 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 O/O 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 O/O measurement. We propose the establishment of a moisture adsorption-degree of substitution or percentage of oxygen-O/O ratio equation, based on the measurement of C%, O% and δO 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 δO by 3.5 mUr under "average" laboratory conditions.
由于暴露的羟基的吸湿性，用目前流行的 EA/Py/IRMS（元素分析/热解/同位素比质谱）方法准确测量陆地植物来源的α-纤维素的 O/O 在天然丰度水平上是一个挑战，因为吸附的水分的 O/O 通常与α-纤维素的 O/O 不同，并且吸附水分的相对量取决于样品和相对湿度。为了将与吸湿性相关的测量误差最小化，我们通过苄基化将α-纤维素的羟基封端到不同程度，发现α-纤维素的 O/O 比值随苄基取代度（DS）的增加而增加，这与理论预测一致，即减少暴露的羟基的存在应该会导致更准确（因此更可靠）的α-纤维素 O/O 测量。我们建议根据不同封端的α-纤维素的 C%、O%和δO 的测量值，建立水分吸附取代度或氧-O/O 比方程，以便可以以特定于植物物种和实验室条件的方式进行稳健的校正。如果不这样做，在“平均”实验室条件下，α-纤维素δO 的平均估计值将低估 3.5 mUr。
