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

Abstract

Rationale Different thermal conversion reactor packings result in distinct δ2H values in nitrogen‐containing materials, such as bone collagen. An older ‘traditional’ glassy carbon packing method causes incomplete conversion of N‐containing samples into H2 gas, resulting in altered δ2H values compared with the complete conversion of hydrogen obtained with a chromium‐packed reactor. Given that δ2H values from collagen are gaining importance in palaeoecological and archaeological studies, a determination of the relationship between δ2H values produced with a glassy‐carbon‐packed and a chromium‐packed reactor is needed. Methods We obtained δ2H values (normalized on the VSMOW‐SLAP scale) from both glassy‐carbon‐packed (GP) and chromium‐packed (Cr) reactor configurations from bone collagen (n = 231) from a variety of archaeological sites, using a High‐Temperature Conversion Elemental Analyzer (TC/EA) coupled to a Delta Plus XP isotope ratio mass spectrometer. Results δ2H values from both methods are linearly correlated (r2 = 0.934) and yield the following interconversion equation, δ2H(Cr) = 1.054 δ2H(GP) + 11.6‰ (95% conf. slope 1.020–1.090, intercept 10.6–12.6), and a mean difference of δ2H(Cr) – δ2H(GP) = 10.1‰ (1 sd 5.2, 1 se 0.3, n = 231). Conclusions We recommend adopting this interconversion between δ2H values produced with a glassy‐carbon‐packed and chromium‐packed reactor for bone collagen only, with appropriate propagation of uncertainty.

Mediterranean precipitation isoscape preserved in bone collagen δ2H

“…In this case δ 18 O lacks geospatial discriminating power in bone collagen. Given the non-trivial analytical challenge in measuring collagen δ 18 O 16,33 , it is noteworthy that δ 2 H can be measured separately and more quickly with a Cr-packed reactor 34,35 , and that δ 2 H values in general have a larger range of variation relative to analytical uncertainty. In sum, the use of hydrogen isotopes is a more promising approach relative to δ 18 O for determination of migrants in the past.…”

“…δ 2 H and δ 18 O values were normalized on the VSMOW-SLAP scale, using VSMOW and SLAP in silver divots as references. The TCEA was packed with a Cr-metal powder filling, as described previously 34,35 , which has been shown to result in quantitative conversion of N-containing organics to H 2 gas 34 . Consequently the δ 2 H data reported here is as obtained by the more newly-developed Cr-packing method.…”

“…We excluded putative diagenetically altered samples by the criteria described in ref. 35 . Excluded samples had (one or more) of the following: lower mass fraction H, lower mass fraction O, or higher O/H ratios (Table S8).…”

Growing up in Ancient Sardinia: Infant-toddler dietary changes revealed by the novel use of hydrogen isotopes (δ2H)

“…Dentin and bone collagen δ 15 N and δ 13 C values were obtained via a Costech Elemental Analyser, using USGS 40 and USGS 41 glutamic acid as standards, and data are reported relative to AIR for δ 15 N and VPDB for δ 13 C. The δ 2 H values of solid materials were obtained using a Thermo Thermal-Conversion Elemental Analyser (TC/EA), previously described in detail [64]. The δ 2 H values of bone collagen, infant feces, breastmilk solids and urine solids were analysed using a chromium (Cr)packed reactor, as described in Reynard et al, 2019 [67]. A subset of dentin samples was analysed at the United States Geological Survey, also using a Cr-packed reactor (see S3 Table for further information).…”

“…A subset of dentin samples was analysed at the United States Geological Survey, also using a Cr-packed reactor (see S3 Table for further information). Tooth dentin δ 2 H measurements were obtained with a glassy carbon furnace packing and were converted to equivalent Cr-reactor-run values using the conversion factor that was also presented by Reynard et al, 2019 [67]. Samples were analysed in duplicate where possible and all δ 2 H data are normalised to the VSMOW-SLAP scale, using VSMOW and SLAP enclosed in sealed silver tubes as standards.…”