Rapid online equilibration method to determine the D/H ratios of non‐exchangeable hydrogen in cellulose

Abstract

An improved method for the determination of deuterium-to-hydrogen (D/H) ratios of non-exchangeable hydrogen in cellulose is presented. The method is based on the equilibration reaction of the hydroxyl hydrogen of cellulose and water vapour of known isotopic composition. The equilibrated cellulose is pyrolysed and the total D/H ratio determined by subsequent online isotope ratio mass spectrometry (IRMS). With a mass balance system the D/H ratio of non-exchangeable hydrogen is recalculated after an empirical calibration has been performed, yielding a mean exchangeability of 0.239 and an equilibrium fractionation factor of 1.082 between the hydroxyl hydrogen of cellulose and water hydrogen at 110 degrees C. Equilibration takes 10 min per sample. Results obtained by this online equilibration method agree very well with values obtained by the nitration technique (R2 = 0.941). The uncertainty of the equilibration method is +/-4 per thousand resulting from a single standard deviation of +/-2.8 per thousand for the equilibration determined by standard cellulose and 2.8 per thousand from the variable exchangeability of the hydroxyl hydrogen in cellulose due to crystalline areas. The latter uncertainty may be lowered by minimising the crystallinity of the cellulose. Advantages of this new technique are (i) the considerably reduced sample amount required (as low as 0.2 mg, ideally 0.5 mg compared with 20 mg for the conventional nitration technique); (ii) an approximately 100-fold reduced process time; and (iii) no need for the hazardous chemicals used in the nitration technique.

An optimized method for stable isotope analysis of tree rings by extracting cellulose directly from cross-sectional laths

“…UV-laser micro dissection, a recent methodological breakthrough, enables analysis of tree rings at higher resolution (Schollaen et al, 2014). However, although stable isotope analysis has become cheaper and faster thanks to advances in mass spectrometry (Brenna et al, 1997;Farquhar et al, 1997;Saurer et al, 1998;Filot et al, 2006), the cellulose extraction process still remains the most laborious and time-consuming part of tree-ring isotope analysis.…”

Multi-isotope labelling of organic matter by diffusion of <sup>2</sup>H/<sup>18</sup>O-H<sub>2</sub>O vapour and <sup>13</sup>C-CO<sub>2</sub> into the leaves and its distribution within the plant

“…The samples for δ 18 O analyses were pyrolysed at 1040 • C in an elemental analyser (EA 1108, Carlo Erba) and transferred via ConFlo III interface (Thermo Finnigan) to the IRMS (Delta plus XL, Thermo Finnigan). The samples for δ 2 H analyses were equilibrated with water vapour of known signature prior to the IRMS measurements in order to determine the isotopic signature of the non-exchangeable hydrogen (as described in Filot et al, 2006;Hangartner et al, 2012). After equilibration the samples were pyrolysed in a thermochemical elemental analyser (TC/EA, ThermoFinnigan) at a temperature of 1425 • C and the gaseous products were carried by a helium stream via a ConFlow II open split interface (Thermo Finnigan) into the IRMS (Isoprime, Cheadle).…”

“…This effect is less expressed for the 2 H / 13 C ratios, since only the fraction of hydrogen that does not exchange with ambient water vapour was measured. The non-exchangeable fraction (74 %) is hydrogen bound to carbon (Filot et al, 2006), which is hardly exchanged with xylem water.…”

Investigating late Holocene variations in hydroclimate and the stable isotope composition of precipitation using southern South American peatlands: an hypothesis

“…For these early pioneers, the sample sizes required for stable isotope measurement were ∼ 5 g, requiring the use of large samples of bulk peat. Recent advances in the use of continuous-flow isotope-ratio mass spectrometry have made it possible to measure δ 18 O and δ 13 C by high temperature pyrolysis (and δD via the additional procedure of nitration or online equilibration) (Gehre and Strauch, 2003;Filot et al, 2006) on cellulose samples that are typically of 0.3-0.35 mg dry weight (Boettger et al, 2007). Analysis of the cellulose fraction of preserved sub-fossil Sphagnum remains has recently been shown to provide reconstructions of the past isotopic composition of precipitation (Daley et al, , 2010.…”