An Untargeted Exposure Study of Small Isolated Populations Using Atmospheric Gas Chromatography Coupled with High Resolution Mass Spectrometry

Significance of the Topic

Human exposure to environmental contaminants is a critical issue linked to diverse health outcomes. Exposomics uses comprehensive analytical workflows to capture a wide spectrum of pollutants. The combination of soft ionization APGC and high-resolution mass spectrometry in a single data-independent acquisition provides both intact molecular ions and informative fragments, enabling deeper insight into exposure patterns.

Objectives and Study Overview

This study compared pooled plasma samples from individuals in five small, geographically isolated coastal communities. It aimed to determine community-specific differences in persistent organic pollutants (POPs) and to discover novel exposure markers through a combined targeted and untargeted workflow.

Methodology and Instrumentation

• Sample Preparation: 2 mL plasma spiked with 13C internal standards, denatured with ethanol/ammonium sulfate, extracted with hexane, cleaned on florisil columns, and concentrated.
• Gas Chromatography: Atmospheric pressure GC (APGC) on Rtx-5MS column, splitless injection, oven ramp from 80 °C to 340 °C over 37.7 min.
• Mass Spectrometry: Xevo G2-XS QTof with APGC universal source in positive mode; MS^E acquisition (low-energy 6 eV; high-energy 30–75 eV); m/z range 50–1000.
• Data Analysis: UNIFI Scientific Information System and Progenesis QI for retention time alignment, targeted MetaScope search (5 ppm precursor, 2 mDa fragment tolerances), multivariate analysis (PCA, OPLS-DA), and database-driven in silico fragmentation against ChemSpider.

Main Results and Discussion

Targeted screening identified 24 POPs across samples, with 11 showing more than twofold variation; Community 1 exhibited the highest levels. Untargeted multivariate analysis (PCA and OPLS-DA) separated community profiles and flagged 17 additional significant markers. ChemSpider searches suggested tocopherol (vitamin E) and benzothiazole in Community 1. Confirmation using an authentic benzothiazole standard validated the untargeted discovery approach.

Benefits and Practical Applications

• Simultaneous targeted and untargeted acquisition reduces sample preparation and analysis time.
• Soft APGC ionization preserves molecular ions while generating structural fragments.
• Advanced software workflows accelerate identification of known contaminants and novel markers.
• Applicable to environmental health monitoring, epidemiological research, and regulatory biomonitoring.

Future Trends and Applications

Future developments may include larger cohort studies, integration of complementary ionization sources, real-time exposome monitoring, and AI-driven data analytics. Coupling this workflow with health outcome data and isotope-labeling strategies could enhance biomarker validation and risk assessment.

Conclusion

The integration of APGC-MS^E with sophisticated data analysis enables comprehensive exposome profiling. This approach successfully distinguished community-specific exposure signatures, identified both known POPs and novel markers, and demonstrated a streamlined pipeline from data acquisition to contaminant confirmation.

References

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