A simple, sensitive method for the simultaneous determination of cotinine and trans-3´-hydroxycotinine in human serum by LC-MS/MS
Bibliographic record
Abstract
Abstract A simple and sensitive liquid chromatography-tandem mass spectrometry (LC-MS/MS) method was developed and validated for the simultaneous determination of cotinine and its metabolite, trans -3´-hydroxycotinine, in human serum. Liquid–liquid extraction (LLE) using dichloromethane (DCM) and ethyl acetate (ETAC) (4:1 v/v) was employed for serum sample extractions. Chromatographic separation was achieved on an Agilent Eclipse Plus Phenyl-Hexyl column (4.6 mm × 100 mm, 5 µm) with a gradient elution of 0.05% (v/v) formic acid/5 mM ammonium formate (1:1) in water and methanol at an initial flow rate of 1 mL/min. Tandem mass spectrometry detection used positive electrospray ionization (ESI) in multiple reaction monitoring (MRM) mode for the determination of cotinine, trans -3´-hydroxycotinine, and their deuterated internal standards. The limits of detection (LOD) for cotinine and trans -3´-hydroxycotinine were 0.005 and 0.006 ng/mL, respectively. The limit of quantification (LOQ) was 0.025 ng/mL for both analytes. The accuracy ranged from 96.1 to 104.9% for cotinine and 98.9 to 102.9% for trans -3´-hydroxycotinine. The linear range for both metabolites was 0.025–10 ng/mL. Extraction recovery ranged from 100.0 to 106.4% for cotinine and 89.6 to 102.5% for trans -3´-hydroxycotinine, respectively. The intra- and interday precision (% CV) ranged from 0.9 to 8.0% for cotinine and 1 to 9.6% for trans -3´-hydroxycotinine. Neither carryover nor endogenous or exogenous interference was observed. The method was successfully applied to pooled serum samples from a biomonitoring study of pregnant women in Alberta, Canada.
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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 | 0.001 | 0.001 |
| Meta-epidemiology (narrow) | 0.000 | 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 | 0.000 | 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".