Hydrogen isotopic analysis with a chromium-packed reactor of organic compounds of relevance to ecological, archaeological, and forensic applications

Abstract

The protein and amino acid δ(2) HVSMOW-SLAP values measured by factory-recommended online HTC methods differ from those from Cr-containing reactor packing. The magnitude of the differences is variable with sample type; the molecular structure and diagenetic history of each sample may be important. Careful attention to this effect is therefore recommended for the δ(2) H measurement for all nitrogen-containing analytes. Copyright © 2016 John Wiley & Sons, Ltd.

The interconversion of δ2H values of collagen between thermal conversion reactor configurations

“…Our average offset between the δ 2 H(Cr) and δ 2 H(GP) values of 10.1‰ (1 sd 5.2, 1 se 0.3, n = 231) compares well with those of three collagens reported by Reynard and Tuross which range from 10.0 ± 0.7‰ (modern cow) to 16.5 ± 4.2‰ (subfossil bison).…”

“…We stress that this offset is relevant for bone collagen only, since other N‐containing and halogen‐ and sulfur‐containing materials have somewhat different δ 2 H values in Cr‐packed vs glassy‐C‐packed reactors.…”

“…In addition, halide acid demineralization produces inconsistent results for oxygen isotopic analysis, and further experimentation is needed to delineate the effects of gelatinization and halide acid demineralization on δ 2 H values . The collagen pseudomorph resulting from EDTA decalcification may have some fine‐scale spatial isotopic variability which then becomes incorporated into the different sample aliquots prepared for mass spectrometry (see Reynard and Tuross for further discussion of pretreatments). The average offset uncertainty is ±5.2‰ (1 sd), and the half‐width of the prediction interval at 68% confidence is 5.0–5.2‰, which are in excellent agreement and slightly larger than our estimate of the usual error of a δ 2 H measurement, as predicted.…”

“…Mass spectrometry conditions and reactor packing were as described previously . We used a High‐Temperature Conversion Elemental Analyzer (TC/EA, also sometimes abbreviated HTC) coupled via a Conflo III interface to a Delta Plus XP isotope ratio mass spectrometer (all from ThermoFinnigan, Bremen, Germany).…”

“…HCN) that are not measured in the mass spectrometer, thus leading to a δ 2 H value that does not reflect all the hydrogen atoms in the sample. A chromium metal based reactor packing has been shown to obviate these difficulties and in collagen and keratin results in a shift in δ 2 H values by 8 to 17‰ compared with the glassy‐carbon‐packed reactor, varying by protein type and mass fraction of nitrogen …”