USGS42 and USGS43: Human-hair stable hydrogen and oxygen isotopic reference materials and analytical methods for forensic science and implications for published measurement results

Assessment of international reference materials for isotope-ratio analysis (IUPAC Technical Report)

“…Chromium has four stable isotopes, 50 Cr, 52 Cr, 53 Cr, and Cr) ratio is about 0.113 and should, in principle, be easy to measure precisely. However, considerable difficulties due to the redox chemistry of chromium can arise during sample preparation for TIMS, limiting attainable uncertainty to about 0.1 ‰.…”

Expanding the Isotopic Toolbox: Applications of Hydrogen and Oxygen Stable Isotope Ratios to Food Web Studies

“…However, some studies have failed to account for H exchange or do not report adequate information about the methods used to do so. Approaches for controlled and repeatable accounting of the exchangeable-H in organic samples have varied (Wassenaar and Hobson, 2003;Bowen et al, 2005a;Kelly et al, 2009;MeierAugenstein et al, 2011;Coplen and Qi, 2012). Some of the recommended methods are described in more detail by Meier-Augenstein et al (2013) and include a two-stage exchange equilibration process (Bowen et al, 2005a), a comparative two-point end-member equilibration (Wassenaar and Hobson, 2000;Kelly et al, 2009), online comparative twopoint end-member equilibration with an autosampler that will allow steam equilibration (EuroVector 1 ), or an online vacuum equilibration system (Wassenaar et al, 2015).…”

“…Currently, no organic international standards for H exist, but laboratory standards that are used should be matched to the unknown sample type in terms of biochemical structure, as the sample composition can affect the proportion of exchangeable H, which will affect equilibration calculations. Two human hair standards, USGS-42 and USGS-43, of known and different isotopic composition are useful in the isotopic analysis of human scalp hair (Coplen and Qi, 2012), and two keratin standards, developed by Environment Canada (Wassenaar et al, 2015), and which can now be purchased through USGS, can be useful for other types of wildlife keratins. As laboratories develop their own internal standards, sharing among the community and referencing to non-exchangeable H isotopic values is encouraged.…”

“…Both δ 2 H and δ 18 O analyses involve the use of pyrolytic combustion techniques and, for δ 18 O, the need to separate the N 2 and CO (i.e., mass 28) peaks for mass spectrometric analysis . While these challenges can be addressed, it is noteworthy that there are still no accepted organic international standards for δ 2 H and δ 18 O measurements (but see Coplen and Qi, 2012;Wassenaar et al, 2015), and many laboratories that routinely run organic materials for δ 13 C, δ 15 N, and δ 34 S measurements are unfamiliar with or not equipped to routinely run organic δ 2 H and δ 18 O measurements (Wassenaar et al, 2015). More fundamentally, there are aspects of animal metabolism involving H and O that present key challenges in understanding metabolic routing and the nature of isotopic discrimination within animals and between trophic levels, which are introduced in the following section and discussed throughout this review.…”

Global spatial distributions of nitrogen and carbon stable isotope ratios of modern human hair

“…Peninsula b -19.7 ±0.8 (116) (2,3); [4,32,36] Southeast Asia c -19.9 ±0.8 (36) (1-3); [4] China -20.1 ±1.3 (297) (3,5); [4,24,37,42,43] Central Asia incl. Mongolia d -20.3 ±0.7 (>29) (2,3); [34,42] Iran, Pakistan -20.4 ±0.4 (30) (3); [4,42] India incl.…”