Soft ionization GC-HRMS of Polychlorinated Biphenyls (PCBs)

Soft Ionization GC-HRMS of Polychlorinated Biphenyls (PCBs)

Importance of the Topic

Polychlorinated biphenyls (PCBs) are persistent environmental pollutants with recognized toxicity and carcinogenicity. Their resistance to degradation leads to long-term cycling in air, water, and soil, raising health and regulatory concerns globally.

Objectives and Study Overview

This study evaluates the use of the SICRIT soft ionization source to couple gas chromatography with high-resolution mass spectrometry (GC-HRMS) on LC-MS platforms. Key goals include:

• Demonstrating effective PCB separation and identification using GC-SICRIT-API-HRMS.
• Assessing the soft ionization mechanism for radical cation detection.
• Evaluating sensitivity, linearity, and detection limits for selected PCB congeners.

Methodology and Instrumentation

A Thermo Trace GC Ultra was linked via the SICRIT® plasma source to a Thermo LTQ Orbitrap XL. The main parameters were:

• Sample: PCB mix (6 congeners) at 10 µg/mL in isooctane.
• Injection: 2 µL, splitless, on RXI-5ms column (30 m × 0.25 mm ID, 0.25 µm film).
• Carrier gas: Helium at 1.2 mL/min; injector at 280 °C; transfer line at 280 °C.
• Temperature program: 40 °C (hold) to 230 °C at 20 °C/min, to 260 °C at 5 °C/min, then to 310 °C at 20 °C/min (hold 2 min).
• Plasma source: SICRIT® at 1.5 kV, 15 kHz, operated with dry nitrogen.
• Detection: Full-scan positive mode, 75–750 m/z, resolution 30,000 FWHM.

Main Results and Discussion

• Successful chromatographic separation of all PCB congeners with distinct retention times.
• HRMS full-scan spectra yielded prominent [M]•+ radical cations with accurate masses within 5 ppm and characteristic chlorine isotope patterns.
• Minimal fragmentation highlights the softness of the DBD-based SICRIT ionization compared to traditional EI methods.
• Calibration studies showed excellent linearity between 20–1000 ng/mL and instrumental LODs below 10 ng/mL for all targets.

Benefits and Practical Applications

The GC-SICRIT-API-HRMS approach offers:

• Non-target full-scan capability for PCB and other non-polar analytes on LC-MS platforms.
• Soft ionization preserving molecular ions for confident compound identification.
• Cost-effective alternative to magnetic sector GC-HRMS instruments.
• Adaptability to existing triple quadrupole, TOF, or Orbitrap systems.

Future Trends and Potential Applications

Expanding this technology may include:

• Analysis of a broader range of low-polarity pollutants and environmental toxins.
• Integration into routine QA/QC workflows for food and environmental monitoring.
• Development of comprehensive non-target screening methods on universal MS platforms.

Conclusion

Coupling GC with LC-MS instrumentation via SICRIT soft ionization enables sensitive, selective, and non-target analysis of PCBs. This strategy bridges the gap between GC and LC-MS, providing a versatile and efficient solution for environmental and industrial analytics.

Reference

• Plasmion GmbH. (2020). Soft Ionization GC-HRMS of Polychlorinated Biphenyls (PCBs). Application Note.