<b>Measurement of emerging dechloranes in human serum using modulated gas chromatography coupled to electron capture negative ionization time‐of‐flight mass spectrometry</b>
Bibliographic record
Abstract
RATIONALE: Quite recently, the presence of significant amounts of several emerging Dechlorane (Dec) flame retardants (FRs) was reported in environmental and biota samples, principally from Canada and China, but also from Europe. Several molecules were identified, e.g. Dec 602, 603, 604, Dechlorane Plus (DP), and Chlordene Plus (CP). Gas chromatography (GC) coupled to electron ionization (EI) high-resolution mass spectrometry (HRMS) is typically used for their measurement in various matrices based on hexachlorocyclopentadiene (HCCPD) fragment ions at m/z 271.8102/273.8072. METHODS: We investigated the use of GC with cryogenic zone compression and electron capture negative ionization time-of-flight mass spectrometry (CZC-GC/ECNI-TOFMS) to measure Dechlorane compounds at low levels in human serum. The TOFMS instrument provided a resolving power of 5000 (FWHM) with an acquisition rate of 25 Hz and was equipped with a specific low thermal emission filament, which allowed it to perform reproducibly in ECNI mode at ion source temperatures as low as 140°C, thus yielding a signal for the molecular ion cluster. RESULTS: The method provided comparable sensitivity to the GC/EI-SectorHRMS technique used in selected ion monitoring (SIM) mode, and specificity for the target Dechlorane compounds. The method was applied on human serum samples and quantification was performed for Dec 602, Dec 603, and CP, ranging from 0.1 to 10 ng/g lipid weight levels. The main drawbacks of the method are the high instrument detection limits (IDLs) obtained for DP and Dec 604. The method would benefit from even softer ionization and better ion transmission. CONCLUSIONS: The main advantages of the present method are the selectivity, as detection is based on the molecular ion signal, and the use of good mass accuracy combined with isotopic distribution calculation for molecular formulae investigation of halogenated compounds. This methodology should facilitate the monitoring of emerging Dechlorane contaminants in future studies, and possibly extend the scope to untargeted emerging analogues. Copyright © 2016 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) | 0.000 | 0.000 |
| Bibliometrics | 0.001 | 0.000 |
| Science and technology studies | 0.000 | 0.000 |
| Scholarly communication | 0.000 | 0.000 |
| Open science | 0.000 | 0.000 |
| Research integrity | 0.001 | 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 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".