Re‐evaluation of the hydrogen stable isotopic composition of keratin calibration standards for wildlife and forensic science applications. (18th June 2017)

• Record Type: Journal Article
• Authors: Soto, David X.; Koehler, Geoff; Wassenaar, Leonard I.; Hobson, Keith A.
• Is Part Of: Rapid communications in mass spectrometry. Volume 31:Number 14(2017)
• Page Start: 1193
• Page End: 1203
• Publication Date: 2017-06-18
• Subjects: Mass spectrometry -- Periodicals; 543.65
• DOI: 10.1002/rcm.7893
• Languages: English
• ISSNs: 0951-4198

Abstract

Abstract : Rationale: Determination of non‐exchangeable hydrogen isotopic compositions ( δ 2 H values) of bulk complex organic materials is difficult due to uncontrolled H isotope exchange between the organic material and ambient water vapor. A number of calibration keratinous materials with carefully measured hydrogen isotopic compositions of the non‐exchangeable fraction were proposed to enable stable isotope laboratories to normalize their 2 H measurements. However, it was recently reported that high‐temperature carbon‐reactor methods for measuring the hydrogen isotopic composition of nitrogenous organic materials is biased by the production of HCN in the reactor. As a result, the reported values of these calibration materials needed to be re‐evaluated. Methods: We evaluated the non‐exchangeable δ 2 HVSMOW values of keratins EC1 (CBS) and EC2 (KHS), USGS hair standards, and a range of other nitrogenous widely used organic laboratory calibration materials (collagen and chitin) using pre‐treatment with a preparation device designed to eliminate residual moisture and quantify exchangeable H. Results: The revised non‐exchangeable δ 2 HVSMOW values of EC‐1 (CBS) and EC‐2 (KHS) keratin standard materials were –157.0 ± 0.9 and –35.3 ± 1.1 ‰, respectively. The revised values of USGS42 and USGS43 were –72.2 ± 0.9 and –44.2 ± 1.0 ‰, respectively, in excellent agreement with previous results. Conclusions: For routine H isotope analyses, with proper sample pre‐treatment, we show that the Comparative Equilibration approach can provide accurate and reproducible non‐exchangeable δ 2 H values among laboratories regardless of the reactor type used. © 2017 Her Majesty the Queen in Right of Canada Rapid Communications in Mass Spectrometry © 2017 John Wiley & Sons Ltd. Reproduced with the permission of the Environment and Climate Change Canada.