Oxygen Isotope Analysis of Saline Solutions by a Carbonic anhydrase-Catalyzed CO<sub>2</sub>–H<sub>2</sub>O Equilibration Method (C<sup>3</sup>HEM) with an Improved Drying Technique
Bibliographic record
Abstract
Abstract The recently introduced carbonic anhydrase-catalyzed CO2–H2O equilibration method (or C3HEM) for oxygen isotopes of aqueous samples has remarkably improved the analytical efficiency of the classic and most popular stable isotope analytical method in geochemistry. However, the applicability of this novel analytical method has not yet been tested for saline/hypersaline solutions despite their significance in various scientific problems. In this study, 1 m chloride and sulfate solutions of geochemical importance were used to investigate the kinetics of oxygen isotope exchange between CO2 and H2O at 25 °C. For these saline solutions, oxygen isotope equilibrium times (EQTs), rate constants, and oxygen isotope salt effects (OISEs) were determined with 4 or 16 μm carbonic anhydrase (CA). Our experimental results reveal that EQTs, ranging from 0.73 to 4.48 h, were much shorter than the typical EQT, confirming the greatly improved analytical efficiency of the C3HEM for saline solutions. In addition, a new simpler CA drying technique was developed, further improving the analytical efficiency of the C3HEM by significantly reducing the required labor time for sample vial preparation. Detailed analytical protocols and practical guidelines of the C3HEM are provided for prospective users.
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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) | 0.000 | 0.000 |
| Bibliometrics | 0.000 | 0.000 |
| Science and technology studies | 0.000 | 0.000 |
| Scholarly communication | 0.000 | 0.000 |
| Open science | 0.000 | 0.000 |
| Research integrity | 0.000 | 0.001 |
| Insufficient payload (model declined to judge) | 0.000 | 0.000 |
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".