Preventing uranium hydride formation in standard uranium samples for determination of<sup>239</sup>Pu by ICP-MS
Bibliographic record
Abstract
UH+ interference poses considerable difficulties for the determination of 239Pu in samples with high uranium content. A new approach for reducing this interference was developed. Substitution of water with heavy water (D2O) as a solvent in uranium standard solution eliminated the major source of UH+ ions and reduced the UH+/U+ ratio from a typical value of 1.33 × 10−5 to a very low value of 2.60 × 10−7. The method allows the determination of low levels of 239Pu in samples containing 106 fold excess of uranium. The detection limit for 239Pu in a sample containing 10 ppm of uranium was determined as 0.58 ± 0.03 ppt. A kinetic isotope effect of ca. 1.4 was observed for the reaction of U+ with hydrogen (H) compared with the reaction with deuterium (D). The magnitude of this effect is in agreement with the value calculated based on the collision theory.
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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 | 0.001 | 0.002 |
| Meta-epidemiology (narrow) | 0.001 | 0.001 |
| Meta-epidemiology (broad) | 0.001 | 0.000 |
| Bibliometrics | 0.001 | 0.001 |
| Science and technology studies | 0.001 | 0.001 |
| Scholarly communication | 0.001 | 0.000 |
| Open science | 0.001 | 0.001 |
| Research integrity | 0.001 | 0.001 |
| Insufficient payload (model declined to judge) | 0.002 | 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".