New and Improved Method for Extracting α-Cellulose for Isotopic Analysis

A team of researchers from Shaanxi University of Science and Technology in Xi’an, China, has developed a new method for extracting α-cellulose from land plants, which has significant implications for environmental, metabolic, and physiological studies. The study, published in the journal Analytical Chemistry, examined the chemical purity and oxygen isotopic composition of α-cellulose extractable from higher plants and its impact on isotopic analysis (1).

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The ¹⁸O/¹⁶O ratio of α-cellulose has been a critical factor in various fields of study, including environmental research. However, current extraction methods may compromise the accuracy of the ratio due to the presence of hemicellulose impurities that are isotopically different from α-cellulose. Hemicellulose impurities in the α-cellulose product obtained with current extraction methods can compromise the reliability of research studies. These impurities have a different isotopic signature from that of α-cellulose, leading to a positive isotopic bias in research results.

To address this issue, the researchers compared the quality of hydrolysates of α-cellulose products obtained from four representative extraction methods and quantified the hemicellulose-derived non-glucose sugars in the α-cellulose products from 40 land grass species using gas chromatography–mass spectrometry (GC–MS). The team found that the Zhou method produced the highest purity α-cellulose with the minimal presence of lignin and the second-lowest presence of non-glucose sugars.

Next, the researchers performed compound-specific isotope analysis of the hydrolysates using GC/Pyrolysis/IRMS, which showed that the O-2–O-6 of the α-cellulose glucosyl units were all depleted in ¹⁸O by 0.0–4.3 mUr (average, 1.9 mUr) in a species-dependent manner relative to the α-cellulose products. The study revealed that the positive isotopic bias of using the α-cellulose product instead of the glucosyl units was due to the pentoses that dominate hemicellulose contamination in the α-cellulose product, which are relatively enriched in ¹⁸O compared to hexoses.

The researchers concluded that the new method for extracting α-cellulose can produce a higher purity product with a lower presence of non-glucose sugars and lignin. This improved method for extracting α-cellulose will benefit various fields of research by providing more reliable data for isotopic analysis.

This study highlights the importance of developing new methods for extracting α-cellulose from land plants to ensure accurate isotopic analysis and to advance our understanding of various scientific disciplines.

Reference

(1) Rani, A.; Zhao, Y.; Yan, Q.; Wang, Y.; Ma, R.; Zhu, Z.; Wang, B.; Li, T.; Zhou, X.; Hocart, C. H.; Zhou, Y. On the Chemical Purity and Oxygen Isotopic Composition of α-Cellulose Extractable from Higher Plants and the Implications for Climate, Metabolic, and Physiological Studies. Anal. Chem. 2023, 95, 11, 4871–4879. DOI: https://doi.org/10.1021/acs.analchem.2c04384