CHEMICAL CHARACTERIZATION OF THE AIRCRAFT CABIN ENVIRONMENT UTILIZING GCxGC-TOFMS AND HARD AND SOFT IONIZATION

Importance of the Topic

Ensuring high air quality inside commercial jets is critical for passenger and crew health. Modern aircraft use pressurized bleed air to maintain cabin pressure at altitudes where unassisted breathing would be impossible. However, engine-derived air can carry trace chemicals from lubricants, hydraulic fluids and environmental contaminants. Understanding this chemical burden helps to identify potential health risks and to improve cabin air management protocols.

Study Objectives and Overview

This work employed a citizen-science approach to collect 98 surface-wipe samples from 62 flights on both bleed-air and non-bleed-air aircraft across multiple carriers and flight durations. The primary goal was to perform a pseudo non-targeted screen for chemical species that are unique or more abundant in bleed-air cabins. Two-dimensional gas chromatography coupled with time-of-flight mass spectrometry (GCxGC-ToFMS) and concurrent hard (70 eV) and soft (16 eV) ionization modes were used to maximize compound coverage and identification confidence.

Methodology

Sample collection focused on high-contact cabin surfaces, with trip blanks included to control for background contamination. Each sample and blank was injected in triplicate under the following conditions:

• Modulation period: 4 s
• Columns: non-polar 1D (25 m) and semi-polar 2D (5 m)
• Injection volume: 2 µL; split ratio 5:1; inlet 300 °C
• Oven program: 60 °C initial, ramp 10 °C/min to 150 °C, then 4 °C/min to 310 °C, hold 5 min (total 54 min)
• Time-of-flight mass range: m/z 30–569
• Daily calibration with deuterated Kovats-Lee mix to track drift

Data were processed with AnalyzerPro XD, applying a proprietary deconvolution and clustering algorithm. Parameters were optimized to balance peak detection sensitivity against false positives. Volcano plots were generated to compare bleed-air and non-bleed-air sample populations.

Instrumentation

The analytical platform comprised:

• GCxGC modulator with 4 s modulation frequency
• Time-of-flight MS detector (Tofwerk) capable of 70 eV and 16 eV ionization
• Non-targeted workflow using simultaneous hard and soft ionization to improve detection of molecular ions and fragments
• Data processing software: AnalyzerPro XD with NIST main library for spectral matching

Main Results and Discussion

Volcano-plot analysis revealed that bleed-air cabins consistently exhibited a larger number of unique and enriched chemical components compared to non-bleed cabins. Representative findings included:

• Boeing 737-600: 13 compounds more abundant, 40 unique
• Airbus A321: 9 compounds more abundant, 36 unique
• Airbus A319 and A330: 23 and 42 compounds respectively more abundant, with no unique compounds in the non-bleed group

From 94 initially detected candidates, a refined subset of 12 compounds passed confidence and chromatographic quality filters. Key analytes included long-chain acids (e.g., nonanoic acid), aldehydes (e.g., decanal) and plasticizers (e.g., di-isononyl phthalate). Soft ionization at 16 eV provided clearer molecular ion signals, aiding in structural elucidation. Although none reached the highest Schymanski identification levels, several warrant future targeted monitoring.

Benefits and Practical Applications

This tandem-ionization GCxGC-ToFMS approach delivers a powerful non-targeted screening workflow capable of:

• Broadly surveying cabin contaminants without prior analyte lists
• Generating suspect lists for targeted follow-up
• Discriminating between bleed-air and non-bleed-air environments

Such data support risk assessments, inform aircraft maintenance protocols and guide the development of real-time air monitoring systems.

Future Trends and Opportunities

Advancements may include:

• Integration of high-resolution MS and tandem MS for confident compound identification at higher Schymanski levels
• Real-time cabin air analysis using field-deployable GC-MS or sensor arrays
• Machine-learning-driven deconvolution and spectral matching to accelerate non-targeted screenings
• Correlating cabin air chemistry with biomonitoring and health outcome data

Conclusion

GCxGC-ToFMS with concurrent hard and soft ionization proved highly effective for non-targeted screening of aircraft cabin contaminants. The study confirms that bleed-air cabins contain a richer and distinct chemical profile compared to non-bleed configurations. These insights establish a foundation for targeted analyses and improved cabin air quality management.