Direct Determination of Si Isotope Ratios in Natural Waters and Commercial Si Standards by Ion Exclusion Chromatography Multicollector Inductively Coupled Plasma Mass Spectrometry
Bibliographic record
Abstract
Silicon isotope ratios in natural waters and several commercial Si standards were determined by online ion exclusion chromatography (IEC) multicollector inductively couple plasma mass spectrometry (MC-ICPMS). As recent studies have shown that mass-independent fractionation (MIF) also exists in MC-ICPMS, e.g., Nd, Ce, W, Sr, Hf, Ge, Hg, and Pb isotopes, the nature of mass bias for Si isotopes was thus investigated. MIF was observed for Si isotopes on both Neptune and Neptune plus MC-ICPMS instruments in this study. Therefore, a standard-sample bracketing (SSB) mass bias correction model, capable of correcting both mass-dependent and mass-independent bias, was employed to obtain accurate Si isotope ratio results in all samples by using NBS28 Si standard as the bracketing standard. Medium resolution was used for all measurements in order to resolve polyatomic interferences on Si isotopes. NBS28 Si standard solutions prepared in nutrient-free seawater and 0.1% NaOH matrix, respectively, were used for the method validation and subjected to the online IEC MC-ICPMS determination of Si isotope ratios. Values of -0.01 ± 0.06 and 0.00 ± 0.06 ‰ (1 SD, n = 10) and -0.01 ± 0.03 and 0.01 ± 0.06 ‰ (1 SD, n = 10) for δ(29/28)Si and δ(30/28)Si, respectively, were obtained, confirming accurate results can be obtained using the reported method for natural waters. Significant variations in Si isotope ratios from -0.72 ± 0.09 to -0.24 ± 0.03 ‰ (1 SD, n = 10) and -1.36 ± 0.11 to -0.46 ± 0.04 ‰ (1 SD, n = 10) for δ(29/28)Si and δ(30/28)Si, respectively, were found among commercial Si standards of NIST SRM3150, SCP Si, and Sigma-Aldrich Si. Values of -0.06 ± 0.07 and -0.20 ± 0.11 ‰ (1 SD, n = 10) for δ(29/28)Si and δ(30/28)Si, respectively, were obtained for the MOOS-3 seawater whereas 0.59 ± 0.11 and 1.19 ± 0.15 ‰ (1SD, n = 10) for δ(29/28)Si and δ(30/28)Si, respectively, were obtained for the SLRS-5 river water. To the best of our knowledge this is the first report of an application of online IEC MC-ICPMS for the high accuracy and precision determination of Si isotope ratios in natural waters. The reported method provides for a relatively rapid (10 min per run) and simple online technique that requires no sample pretreatment for the Si isotope ratio measurements.
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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 | 0.000 |
| Meta-epidemiology (broad) | 0.000 | 0.000 |
| Bibliometrics | 0.001 | 0.001 |
| Science and technology studies | 0.000 | 0.001 |
| Scholarly communication | 0.000 | 0.000 |
| Open science | 0.001 | 0.001 |
| Research integrity | 0.000 | 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".