Re‐evaluation of the hydrogen stable isotopic composition of keratin calibration standards for wildlife and forensic science applications
Bibliographic record
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 H VSMOW 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 H VSMOW 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.
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How this classification was reachedexpand
Full frame machine prediction
Teacher imitationNot calibrated prevalence, not ground truth. Human validation pending. The Gemma side is a direct model label for every work in the frame, read from the title-only record. The Codex side is a classifier learned from the 10,348 direct Codex labels and calibrated to design-weighted sample rates; fields without enough sample support carry no Codex call. Candidate is the union of the two sides; consensus is their intersection. These outputs are machine_predicted_unvalidated and are not human labels.
Distilled classifier scores by category (both heads)
| Category | Codex | Gemma |
|---|---|---|
| Metaresearch | 0.006 | 0.006 |
| Meta-epidemiology (narrow) | 0.001 | 0.000 |
| Meta-epidemiology (broad) | 0.000 | 0.000 |
| Bibliometrics | 0.001 | 0.001 |
| Science and technology studies | 0.001 | 0.001 |
| Scholarly communication | 0.001 | 0.001 |
| Open science | 0.001 | 0.001 |
| Research integrity | 0.001 | 0.001 |
| Insufficient payload (model declined to judge) | 0.001 | 0.001 |
Machine scores (provisional)
The two teacher heads of the student model, read on this work. A score orders the frame for review; it never asserts a category, and the validation status ships verbatim with every row.
Baseline scores from an immature model (maturity gate not passed, 7 training rounds). Scores rank; they never assert a category.
score_only:v0-immature-baseline · verbatim from the scoring run: score_only means the number may rank works, and no category label ships from itClassification
machine, unvalidatedMachine predicted; a candidate call from one source (direct Gemma or distilled Codex), not a consensus.
How this classification was reached, model by model and score by score, is at the end of the page under "How this classification was reached".