A simplified silver phosphate extraction method for oxygen isotope analysis of bioapatite
Bibliographic record
Abstract
Rationale Although phosphatic materials are chemically complex and are prone to exchange oxygen isotopes with their environments, the phosphate (PO 4 3− ) component of these materials is robust and retains its original oxygen isotopic composition. As a result, there are currently several methods for the isolation of phosphate oxygen through the precipitation of silver phosphate (Ag 3 PO 4 ). However, some of these techniques produce Ag 3 PO 4 of questionable purity, while nearly all are lengthy and/or require relatively large sample sizes. Methods Five milligrams of bioapatite from modern cow teeth (enamel and cementum) were pre‐treated for removal of organic material prior to digestion in 2 M HF. The digested samples were titrated with silver ammine solution at 50°C to precipitate Ag 3 PO 4 . Oxygen isotopic data were collected using a Thermal Combustion Elemental Analyzer (TC/EA) paired with a Delta V Plus isotope ratio mass spectrometer via a ConFlo III universal interface. Results The quality of Ag 3 PO 4 is dependent on effective removal of organic material and the volume of silver ammine solution used during titration. A two‐step pre‐treatment of 2.5% NaOCl, followed by a 0.125 M NaOH solution, is the most effective treatment for the removal of organic material from both enamel and cementum. Optimal yields of Ag 3 PO 4 were achieved using 1.8 mL of silver ammine solution. The reproducibility of the phosphate δ 18 O compositions ranges from 0.3 to 0.4‰ (1σ) for modern cow teeth. Conclusions We present a simplified method for phosphate extraction from organic‐rich phosphatic material. Our method gave reproducible δ 18 O values for enamel and cementum from cows' teeth.
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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 | 0.000 | 0.001 |
| Meta-epidemiology (narrow) | 0.001 | 0.000 |
| Meta-epidemiology (broad) | 0.001 | 0.000 |
| Bibliometrics | 0.001 | 0.001 |
| Science and technology studies | 0.000 | 0.000 |
| Scholarly communication | 0.000 | 0.000 |
| Open science | 0.001 | 0.000 |
| Research integrity | 0.001 | 0.001 |
| Insufficient payload (model declined to judge) | 0.004 | 0.004 |
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".