Development of a high performance liquid chromatography method to monitor the biodegradation of naphthenic acids
Bibliographic record
Abstract
Naphthenic acids are found in wastewaters from petroleum refineries and from the extraction process used to recover bitumen from large oil sands deposits found in northeastern Alberta, Canada. The naphthenic acids, comprised mainly of a complex mixture of carboxylic acids, are toxic to many forms of aquatic life. Previous studies have shown that biodegradation in natural settings or in laboratory cultures reduces the toxicity of naphthenic acids. A high performance liquid chromatography (HPLC) method was developed to follow the removal of naphthenic acids from aerobic, laboratory cultures. Small samples of the culture supernatants (100 μμL) were derivatized with 2-nitrophenylhydrazine, and the derivatized carboxylic acids were separated from the excess derivatizing agent by HPLC. The derivatized acids eluted as an unresolved hump in the chromatogram. Comparing the areas under the humps in standard preparations (containing 5200 mg naphthenic acids/L), and in culture supernatants allowed measurements of the depletion of naphthenic acids from the microbial cultures. Three naphthenic acids preparations were studied, and up to 40% of the naphthenic acids were removed by cultures during 30- to 40-d incubation periods. Carbon dioxide formation accompanied the decrease in the naphthenic acids concentration determined by HPLC. Key words: biodegradation, high performance liquid chromatography, naphthenic acids, 2-nitrophenylhydrazine, oil sands.
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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) | 0.000 | 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 | 0.000 |
| 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".