A Comprehensive Liquid-State Heteronuclear and Multidimensional NMR Study of Laurentian Fulvic Acid
Bibliographic record
Abstract
The Boreal forest fulvic acid known as Laurentian fulvic acid (LFA) has been interrogated by state of the art heteronuclear and 2D high resolution NMR techniques. It is shown that one can obtain very highly resolved and informative spectra of a traditionally fractionated material. It was possible to observe a proton coupled system of up to seven bonds in the TOCSY spectrum and 329 peaks in the 1H,13C-HSQC spectrum. It is found that the majority of the nitrogen in this sample is in the form of ammonium cations. From the combination of inverse-gated decoupling, APT, and INEPT 13C spectra of LFA it can be concluded that while the aromatic moieties of LFA are highly unfunctionalized, the carbohydrate moieties are highly functionalized. Proton coupled networks are observed in the TOCSY spectrum between and within the aliphatic, functionalized aliphatic, and heteroatom substituted regions and, to a lesser extent, also between the amine/aromatic and heteroatom substituted regions. The HMBC spectrum confirms that both the aliphatic and heteroatom moieties are highly functionalized with carboxylic and alcoholic functional groups, while the aromatic moieties are very sparsely functionalized with phenolic and carboxylic functionalities. Additionally, specific model molecular structures have been identified which are consistent with experimental evidence and are in full agreement with our previously derived meso-model based on solid-state 13C NMR data. Finally, some of the shortcomings of 2D liquid-state NMR for the characterization of humic materials are addressed.
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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 | 0.000 | 0.000 |
| Meta-epidemiology (narrow) | 0.000 | 0.000 |
| Meta-epidemiology (broad) | 0.000 | 0.000 |
| Bibliometrics | 0.000 | 0.000 |
| Science and technology studies | 0.000 | 0.001 |
| Scholarly communication | 0.000 | 0.000 |
| Open science | 0.000 | 0.000 |
| Research integrity | 0.000 | 0.000 |
| 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 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".