Determination of low concentrations of platinum group elements in geological samples by ID-ICP-MS
Bibliographic record
Abstract
Accurate and precise determination of platinum group elements (PGEs) at ppb concentrations in geological samples is important but problematic. This paper reports an improved analytical method for the determination of Pt, Pd, Ru, Ir and Rh at sub-ppb levels by isotope dilution-inductively coupled plasma mass spectrometry (ID-ICP-MS). Prior to experimentation, all reagents were carfully purified: HBO3, HCl and SnCl2 by Te coprecipitation and HNO3 and HF by subboiling distillation. HF, HNO3 and HCl were used to decompose 10 gram sample. The fluoride residue from the acid digestion is minimized by using H3BO3 for complexation, thus mini-fusion of sodium peroxide can be performed in corundum crucibles instead of bulk Na2O2 fusion to lower blank level. The solution of acid digestion and Na2O2 fusion are combined and PGEs are then pre-concentrated by Te coprecipitation. Cu, Ni, Zr and Hf are removed using cation exchange resin and P507 extraction chromatography resin combined in the same column to minimize their interference. Pt, Pd, Ru and Ir are determined using ID-ICP-MS, whereas the mono-isotopic element, Rh, is determined by external calibration using highly enriched 194Pt as the internal standard. The enriched 194Pt spike behaves similar to Rh during the Te precipitation procedure and acts as an ideal internal standard. The determination limits for PGE range from 0.01–0.19 ng g−1. The results obtained using this new method for the CCRMP (CANMET, Ottawa, Canada) certified reference materials WGB-1 (gabbro), TDB-1 (diabase) and UMT-1 (ultramafic ore tailings), show good agreement with the reported values, but have discrepancies compared with the certified values when the concentration of Ru, Rh and Ir below 0.5 ng g−1.
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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 | 0.001 |
| 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 | 0.001 | 0.000 |
| 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".