The effect of processing medium on the 2H/1H of carbon-bound hydrogen in α-cellulose extracted from higher plants

Rationale Although the H-2/H-1 ratio of the carbon-bound hydrogens (C-Hs) in alpha-cellulose extracted from higher plants has long been used successfully for climate, environmental and metabolic studies, the assumption that bleaching with acidified NaClO2 to remove lignin before pure alpha-cellulose can be obtained does not alter the H-2/H-1 ratio of alpha-cellulose C-Hs has nonetheless not been tested. Methods For reliable application of the H-2/H-1 ratio of alpha-cellulose C-H, we processed plant materials representing different phytochemistries and photosynthetic carbon assimilation modes in isotopically contrasting bleaching media (with an isotopic difference of 273 mUr). All the isotope ratios were measured by elemental analyzer/isotope ratio mass spectrometry (EA/IRMS). Results Our results show that H from the bleaching medium does appear in the final pure alpha-cellulose product, although the isotopic alteration to the C-H in alpha-cellulose due to the incorporation of processing H from the medium is small if isotopically natural water is used to prepare the processing medium. However, under prolonged bleaching such an isotope effect can be significant, implying that standardizing the bleaching process is necessary for reliable H-2/H-1 measurement. Conclusions The currently adopted method for removing lignin for alpha-cellulose extraction from higher plant materials with acidified NaClO2 bleaching is considered acceptable in terms of preserving the isotopic fidelity if isotopically natural water is used to prepare the bleaching solution.