Open Characterization of 2.5 Micron, Particulate-Borne Semi-Volatile Organic Compounds by GC-TOFMS and UHPLC Orbitrap MS: Method Development, Performance and Applications

Importance of the Topic

Exposure to fine particulate matter (PM2.5) poses significant health risks due to associated semi-volatile organic compounds (SVOCs) such as polycyclic aromatic hydrocarbons (PAHs), pesticides and pharmaceutical residues. Detailed chemical characterization of SVOCs on PM2.5 filters closes critical knowledge gaps in air quality monitoring, source identification and risk assessment.

Objectives and Study Overview

This work demonstrates a combined workflow for the open characterization of PM2.5-borne SVOCs collected on TEOM filters. It develops and evaluates methods for both targeted analysis of PAHs by GC-TOFMS and non-targeted screening of polar SVOCs by UHPLC Orbitrap MS. Field samples from two urban sites were analyzed for performance assessment and application potential.

Instrumentation

• TEOM tapered element oscillating microbalance with 15 mm PTFE filters (3 L/min, 60 days)
• LECO Pegasus III GC-TOFMS with DB-5 (30 m × 0.25 mm × 0.25 μm) column and helium carrier
• Thermo Scientific UltiMate 3000 UHPLC (HRG-3400RS pump, WPS-3000 autosampler, TCC-3400)
• UHPLC columns: BetaSil coreshell for positive mode and XB C18 coreshell for dual mode
• Thermo Exactive Plus Orbitrap MS with H-ESI II source (resolving power 140 000 @ m/z 200, 5 ppm mass extraction)
• Data processing: LECO ChromaTOF, Thermo Xcalibur and TraceFinder software with PAH, pesticide (565-compound) and emerging organic compound (382-compound) databases

Methodology

• Filter extraction by ultrasonic agitation in HPLC-grade acetonitrile (2×15 min), filtration (0.2 μm), concentration and reconstitution to 100 μL
• GC-TOFMS acquisition: full‐scan TOF at >1.5 scans/s, NIST library deconvolution, targeted PAH quantitation
• UHPLC Orbitrap MS: positive/negative scans, adducts (M+H, M+NH₄, M+Na, M–H), automatic gain control, 50 ms C-trap inject
• TraceFinder screening criteria: XIC area threshold ≥50 000, mass accuracy ≤2 ppm, isotopic pattern (M+1) intensity ≥90%, retention time matching where standards available

Main Results and Discussion

• Targeted GC-TOFMS quantified 4- to 6-ring PAHs (phenanthrene, pyrene, B(b)fluoranthene) with detection limits 2–7 ng per filter; 2- and 3-ring PAHs were largely lost by breakthrough
• Non-targeted UHPLC Orbitrap MS identified bisphenol A in 7 of 10 filters and other polar SVOCs including pharmaceuticals (ibuprofen, gemfibrozil), pesticides (dinoseb) and surfactants
• Pesticide screening revealed herbicide Flamprop-M-isopropyl and tobacco marker nicotine in most samples
• False positive example: gemfibrozil passed accurate mass and isotopic criteria but failed retention time confirmation, underscoring need for orthogonal data
• Complementarity of GC and UHPLC platforms broadened coverage of hydrophobic and polar SVOCs

Benefits and Practical Applications

• Comprehensive SVOC profiling on archived PM2.5 filters enhances air quality studies
• High-resolution MS workflows enable simultaneous targeted and suspect screening with retrospective data mining
• Supports source apportionment, regulatory monitoring and human exposure assessments

Future Trends and Applications

Advances in high-throughput HRMS, expanded spectral libraries and machine-learning‐driven data interpretation will further improve screening confidence. Integration of quantitative workflows, real-time sensors and miniaturized sampling will extend applicability in environmental surveillance and exposure science.

Conclusion

This study validates a dual-platform approach combining GC-TOFMS and UHPLC Orbitrap MS for open characterization of PM2.5-borne SVOCs. The workflow enables detection of both hydrophobic PAHs and polar emerging contaminants, though orthogonal confirmation (retention time, fragment ions) remains essential for minimization of false positives.

Reference

• Ontario Ministry of the Environment. Method E3480: Determination of PAHs in Water by GC-TOFMS.
• Ontario Ministry of the Environment. Method E3454: Determination of Emerging Organic Pollutants by LC-MS/MS.
• SANCO/12495/2011. Method Validation and Quality Control for Pesticide Residue Analysis in Food and Feed.