Development of a LC/MS Method for Analysis of Total Vicinal Diketones in Beer
Bibliographic record
Abstract
A liquid chromatography/mass spectrometry (LC/MS) method was developed for the simultaneous determination of vicinal diketones (VDK), diacetyl and pentanedione, in beer. Diacetyl and pentanedione were derivatized with o-phenylenediamine (OPDA) to form quinoxaline compounds. Total VDK were measured directly over a concentration range of 10 μg/L to 10 mg/L with less than 10% variation. The reaction of VDK with OPDA was studied to optimize reaction time. Decarboxylation of the diacetyl precursor α-acetolactate was evaluated using two decarboxylation techniques. Attempts to simultaneously determine the amino acids leucine, isoleucine, and valine as well as the VDK in beer were successful, but only for amino acid concentrations up to 10 mg/L. Because levels of amino acids found in wort are generally higher than this, sample dilution and separate injections were required. Samples were collected from a local commercial brewery and analyzed for total VDK to further evaluate the method's practical application.
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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 | 0.001 |
| Meta-epidemiology (broad) | 0.001 | 0.000 |
| Bibliometrics | 0.002 | 0.001 |
| Science and technology studies | 0.001 | 0.000 |
| Scholarly communication | 0.001 | 0.001 |
| 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".