Characterization of PFAS and Other Pollutants in Household Dust Using GCxGC-HRTOFMS and Spectral Analysis Tools (SAT)

Significance of the topic

Household dust accumulates a broad spectrum of anthropogenic chemicals and serves as an accessible matrix for assessing human exposure to legacy and emerging pollutants. Comprehensive, untargeted screening of dust is essential because many hazardous compounds—notably volatile and neutral forms of per- and polyfluoroalkyl substances (PFAS)—are poorly covered by routine targeted methods. High chromatographic resolution combined with high-resolution accurate-mass detection and tailored data mining enables discovery, class-specific filtering, and confident annotation of trace contaminants in very complex matrices.

Objectives and study overview

This work developed and demonstrated an untargeted GCxGC–high-resolution time-of-flight mass spectrometry (HRTOFMS) workflow to characterize a NIST house dust standard (SRM 2585) and representative household/office dust samples. The goals were to (1) comprehensively profile diverse chemical classes present in dust, (2) detect and annotate volatile and semi-volatile PFAS and other persistent organic pollutants (POPs), and (3) illustrate how complementary ionization modes and advanced spectral analysis tools simplify data review and increase annotation confidence.

Methodology and data processing

The sample preparation used a simple solvent extraction: ~0.14 g dust extracted twice with dichloromethane/hexane (3:1) by sonication, centrifugation, filtration, solvent evaporation under N2, and reconstitution in dichloromethane for GC analysis. Two-dimensional gas chromatography (GCxGC) provided enhanced separation of complex mixtures. Data acquisition exploited multiple ionization modes—electron ionization (EI), positive chemical ionization (PCI), and negative chemical ionization (NCI)—collected on a Pegasus HRT+ 4D HRTOFMS equipped with a multi-mode source.
Data processing combined automated untargeted Peak Find (deconvolution, spectral-similarity searching, retention-index filtering and elemental/formula assignment using HRAM ions) with Spectral Analysis Tools (SAT) and Target Analyte Finding (TAF). SAT’s scaled mass-defect plotting (e.g., scaling by CF2 for fluorinated series or by Cl-H for chlorinated congeners) was used to filter thousands of markers and highlight compound classes on simplified contour (XIC) plots. TAF applied a target list of retention windows and HRAM ions for confirmation after class localization.

Used instrumentation

• LECO Pegasus HRT+ 4D high-resolution time-of-flight mass spectrometer with Multi-Mode Source (MMS) capable of EI, PCI, and NCI.
• Comprehensive two-dimensional gas chromatograph (GCxGC) with QuadJet thermal modulation.
• Data analysis software: automated Peak Find/deconvolution, Spectral Analysis Tools (SAT) including mass-defect plotting and scaled filtering, and Target Analyte Finding (TAF).

Main results and discussion

• The untargeted workflow produced confident annotations across many chemical classes: hydrocarbons, acids, amines, alcohols, aldehydes, ketones, phenols, terpenes, fatty acids, steroids, phosphates, illicit and over-the-counter drugs, and multiple POPs.
• SAT mass-defect scaling substantially simplified interpretation of dense GCxGC contour plots, enabling rapid localization of PFAS families (e.g., fluorotelomer alcohols — FTOHs, and perfluorooctane sulfonamide ethanol derivatives — FOSEs) and chlorinated POPs (PCBs, chlordanes).
• Complementary ionization modes were critical for robust annotation: many PFAS homologs lacked molecular ions in EI spectra, causing ambiguous or incorrect library matches. PCI provided strong protonated molecular ions and high isotopic-fidelity matches (example: N‑MeFOSE observed [MH]+ at m/z 558.00217 with −0.81 ppm mass error and isotopic fidelity ≈980/1000), enabling correct formula assignment and confirmation.
• NCI-HRT data targeted electronegative chlorinated species, and when combined with SAT mass-defect filtering (Cl-H scaling) and TAF processing, enabled annotation of PCBs and chlordanes in the SRM dust sample.
• TAF used retention time windows and HRAM ions derived from the data review to provide targeted confirmation of class members after class-level localization by SAT. Results included annotation of multiple FTOHs, FTOSEs, PCBs and chlordanes at trace levels (details summarized qualitatively; tabulated peak areas and S/N were reported in the original study).

Benefits and practical applications of the method

• Comprehensive untargeted GCxGC–HRTOFMS screening captures a wide chemical space in a single workflow, reducing the need for multiple targeted assays for different analyte classes.
• Multi-mode ionization (EI/PCI/NCI) yields complementary spectral information—fragmentation patterns plus intact molecular ions and isotopic fidelity—improving confidence in structural and elemental assignments, especially for PFAS where EI alone is often insufficient.
• SAT mass-defect scaling and visualization accelerates data triage by displaying only analytes with specific elemental composition (e.g., F- or Cl-containing), which is highly valuable for exposure assessments and forensic screening of indoor environments.
• The approach supports discovery of emerging or volatile PFAS that may be absent from conventional targeted databases, informing risk assessments and regulatory monitoring priorities.

Future trends and applications

• Expansion and curation of spectral libraries for neutral and volatile PFAS, including CI spectra, will improve automated matching and reduce misannotations.
• Integration of GCxGC–HRMS workflows with LC–HRMS data (to capture ionic PFAS) and orthogonal techniques will yield a more complete exposure profile for dust and indoor matrices.
• Further automation and machine-learning–based prioritization of candidates, coupled with rule-based mass-defect filtering, can speed identification in very large datasets.
• Advances in ion sources and modulators increasing sensitivity and robustness will lower detection limits for trace POPs and expand applicability to low-mass microgram samples.
• Standardized TAF lists and retention-index libraries for PFAS/POPs will improve inter-laboratory comparability and routine surveillance capabilities.

Conclusion

The combined use of GCxGC separation, high-resolution accurate-mass TOF detection, complementary ionization modes, and advanced spectral analysis tools provides a powerful, flexible workflow for untargeted screening of household dust. Scaled mass-defect plotting and TAF enable rapid localization and confident confirmation of PFAS and other trace POPs that are otherwise difficult to find with classical targeted approaches. This integrated strategy supports comprehensive environmental monitoring, exposure assessment, and the discovery of emerging contaminants in complex indoor matrices.

Reference

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2. Haglund P., et al., The strength in numbers: comprehensive characterization of house dust using complementary mass spectrometric techniques, Analytical and Bioanalytical Chemistry, 2019, 411, 1957–1977.
3. Alonso D.E., Richards T., Comprehensive Screening of Pollutants in Household Dust Using High-Resolution Mass Spectrometry with Enhanced Chromatographic Resolution, Current Trends in Mass Spectrometry, 2022, 20(1), 7–12.