Routine hydrogen isotope measurement of cellulose nitrate by high‐temperature pyrolysis – reference materials and precision

Abstract

The determination of isotope ratios of non-exchangeable hydrogen in tree-ring cellulose is commonly based on the nitration of wood cellulose followed by online high-temperature pyrolysis and isotope ratio mass spectrometry measurement of cellulose nitrate samples. The application of this method requires a proper calibration using appropriate reference materials whose delta(2)H values have been reliably normalized to the V-SMOW/SLAP scale. In our study, we achieve this normalization by a direct alternating measurement of reference waters (V-SMOW and SLAP) and three cellulose nitrates chosen as reference materials. For that purpose, both water and solid organic samples are introduced into the pyrolysis reactor by silver capsule injection. The analytical precision of the water measurement using the capsule method is +/-1.5 per thousand. The hydrogen isotopic composition of three cellulose nitrate standards measured ranges from -106.7 to -53.9 per thousand. The standard deviation of the calculated means from five measurement periods of those standards is better than 1 per thousand. Twenty-four different measurements of the hydrogen isotope composition of cellulose nitrate were evaluated in order to assess the precision of the described method. We obtained an analytical precision of +/-3.0 per thousand as representative for the 95% confidence interval applicable for routine measurements of cellulose nitrate samples. Evidence was found for significant differences in the behavior of cellulose nitrate and PE foil during the pyrolitic conversion that emphasizes the need for a proper calibration of the routine measurements. This calibration can only be successful if the reference materials used have a very similar chemical composition and undergo the same preparation procedure as the samples.

Summer maximum temperature in northern France over the past century: instrumental data versus multiple proxies (tree-ring isotopes, grape harvest dates and forest fires)

“…In addition, the inter-annual standard deviation is twice as large for one station (8.1 ) compared to the other (4.8 ) over the same period. Knöller et al (2007) observed a difference up to 47.3 between replicates of a standard. They attribute this large variation to evaporative effects during the analysis procedure.…”

“…The determination of non-exchangeable δD values in cellulose are based on nitration of wood cellulose (Alexander and Mitchell 1949), followed by online combustion and IRMS measurements of cellulose nitrate samples (Knöller et al 2007). The calibration with respect to the IAEA-VSMOW standard is performed with the two long-term validated versus IAEA-VSMOW and IAEA-SLAP wood cellulose nitrate standards.…”

Investigation of preparation techniques for δ2H analysis of keratin materials and a proposed analytical protocol

“…[3][4][5][6] The advent of continuous-flow isotope-ratio mass spectrometry (CF-IRMS) coupled with thermal conversion elemental analyzers (TC/EAs) has enhanced δ 2 H measurements by allowing analysis of smaller sample sizes with faster sample throughput. [15][16][17] Despite these advances, there are shortcomings in the analytical protocols because the same hydrogen isotopic composition may not be obtained in different laboratories for the same homogeneous keratin material.…”

Novel silver‐tubing method for quantitative introduction of water into high‐temperature conversion systems for stable hydrogen and oxygen isotopic measurements

“…Because atmospheric oxygen is trapped in capsules with water, a correction must be made for its amount and isotopic composition. Knöller et al 10. used a strategy to minimize the effects of evaporation during weighing by weighing water under an argon atmosphere and loading an amount of water about 2 to 10 times larger (2 µL) into capsules.…”