Precise isotope ratio determination of common Pb using quadrupole LA-ICP-MS with optimized laser sampling conditions and a robust mixed-gas plasma
Bibliographic record
Abstract
This work presents a method for the precise (0.2% RSE) determination of common (i.e. non-radiogenic) Pb isotope ratios using quadrupole Nd:YAG (266 nm) LA-ICP-MS at low (∼2 ppm) Pb concentrations. Laser sampling conditions significantly influence the precision of Pb isotope ratio measurements. This paper presents a set of optimum sampling conditions for the described system. Setting the laser focus above the sample surface significantly improves the precision of ratio measurements due to increased count rates and a reduction in the heterogeneity of particulate matter produced by fracturing at the site of ablation. In addition, using a more robust, mixed-gas (Ar–N2) plasma significantly increases sensitivity and reduces mass bias. With a mixed Ar–N2 plasma and optimized laser sampling conditions, single collector quadrupole LA-ICP-MS can be superior, for some applications (e.g., where micrometre-scale spatial resolution is important), to TIMS, and at low Pb concentrations is a cost-effective alternative to LA-MC-ICP-MS. The application of single detector, quadrupole LA-ICP-MS to the precise determination of common Pb isotope ratios in minerals has not been previously documented. This method is a powerful tool for use in isotope tracer studies of ore deposits and has potential applications to a range of environmental problems.
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How this classification was reachedexpand
Full frame distilled prediction
Teacher imitationNot calibrated prevalence, not ground truth. Human validation pending. Learned from the 10,348 direct Codex labels and 10,348 direct Gemma labels. Candidate is the union of thresholded teacher heads; consensus is their intersection. These outputs are machine_predicted_unvalidated and are not human labels or direct frontier model labels.
Codex and Gemma teacher scores by category
| Category | Codex | Gemma |
|---|---|---|
| Metaresearch | 0.001 | 0.001 |
| Meta-epidemiology (narrow) | 0.000 | 0.000 |
| Meta-epidemiology (broad) | 0.001 | 0.000 |
| Bibliometrics | 0.000 | 0.001 |
| 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) | 0.001 | 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 teacher head, 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".