Ion-pair HPLC determination of hydroxycinnamic acid monoconjugates of putrescine, spermidine and spermine
Bibliographic record
Abstract
The terminal hydroxycinnamic acid monoconjugates of putrescine, spermidine and spermine were resolved and quantified in extracts of plant tissues using sodium hexanesulphonate as an ion-pair reagent and a double methanol gradient. Extracts were prepared from acidic methanol:water (80:20) that had been back-extracted with hexane, and fractionated on C-18 solid phase extraction and carboxymethyl cation exchange cartridges. The chromatographic conditions were capable of separating N1- and N8-coumaroyl and feruloyl spermidine, which differ only by the disposition of the secondary amine in the polyamine side chain. Reliable detection limits for most compounds were less than 5 µg/mL (approximately 10−5 M in the plant extract) and extraction efficiencies were 91% as determined using the novel internal standard, N1-coumaroyl hexanediamine. Copyright © 2000 John Wiley & Sons, Ltd.
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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) | 0.001 | 0.000 |
| Bibliometrics | 0.001 | 0.001 |
| Science and technology studies | 0.001 | 0.000 |
| Scholarly communication | 0.000 | 0.000 |
| Open science | 0.000 | 0.000 |
| 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".