Comprehensive Analysis of Short-Chained Chlorinated Paraffinsand other POPs in Environmental Samples by GCxGC-HR-TOFMS with a Novel Ion Source

Significance of the Topic

The analysis of short-chain chlorinated paraffins (SCCPs) and other persistent organic pollutants (POPs) in environmental samples is critical due to their persistence, bioaccumulation potential, and toxicological effects. State-of-the-art analytical methods are required to resolve complex mixtures of isomers and co-contaminants in matrices such as dust and sediments. Integrating GCxGC with high-resolution TOFMS and a versatile ion source enhances selectivity and sensitivity, supporting regulatory compliance and environmental risk assessment.

Objectives and Study Overview

This work evaluates a prototype dual-chamber ion source operating in electron ionization (EI), positive chemical ionization (PCI), and electron capture negative ionization (ECNI) modes, coupled with comprehensive GCxGC-HR-TOFMS. The primary goals are to develop and optimize analytical protocols for SCCP standards with varying chlorination levels, and to apply the method to real environmental dust samples to demonstrate qualitative screening capabilities.

Instrumentation

• Gas chromatograph: Agilent 7890B with LECO dual-stage quad-jet liquid nitrogen-cooled thermal modulator
• Mass spectrometer: LECO Pegasus GC-HRT+ 4D high-resolution TOFMS, resolving power ≥25 000, mass accuracy ≤1 ppm
• Ion source: novel dual-chamber design supporting EI, PCI (reagent gas CH₄), and ECNI modes without hardware changes

Methodology

Injection was performed in splitless mode (1 µL, 270 °C). Column 1 was Rxi-1ms (30 m × 0.25 mm × 0.25 µm) and Column 2 was DB-XLB (1.2 m × 0.1 mm × 0.1 µm). The primary oven ramped from 100 °C to 300 °C with controlled heating rates, while the secondary oven was offset by +5 °C and followed a complementary program. Modulation period was 4.5 s. Acquisition covered m/z 25–1 000 in ECNI and m/z 15–1 000 in EI at 200 spectra/s. Transfer line and source temperatures were optimized for each ionization mode.

Main Results and Discussion

• Distinct GCxGC patterns were observed for three SCCP standards with 63 % chlorination and varying chain lengths, enabling isomer discrimination via extracted ion chromatograms (XIC) for (M–Cl)⁻ and (M–HCl)⁻ fragments.
• Environmental samples (e-waste dust, household dust, marine sediment SRM) were qualitatively screened under ECNI conditions, confirming the presence of multiple SCCP congeners and co-occurring POPs such as PCBs.
• The novel ion source provided stable high-resolution spectra, with improved sensitivity in negative ion mode compared to conventional ECNI sources, facilitating reliable screening in complex matrices.

Benefits and Practical Applications

This approach delivers:

• Enhanced separation of structurally similar chlorinated compounds through two-dimensional chromatography.
• Superior selectivity and mass accuracy from high-resolution TOFMS, reducing interferences.
• Flexible ionization modes without hardware swaps, streamlining method development for a variety of analyte classes.

These capabilities support environmental monitoring laboratories, regulatory agencies, and research studies focused on POPs distribution and transformation.

Future Trends and Opportunities

Future developments may include:

• Quantitative method validation for SCCPs and other halogenated contaminants in diverse matrices.
• Automation of data processing workflows using advanced deconvolution and machine-learning algorithms to handle large GCxGC-HRMS datasets.
• Integration with complementary techniques (e.g., LC-HRMS) for broader POPs coverage.
• Application to emerging contaminants and suspect screening in environmental and biological samples.

Conclusion

The combination of comprehensive two-dimensional GC, a high-resolution TOFMS, and a novel multi-mode ion source provides a powerful platform for the qualitative analysis of SCCPs and related POPs in complex environmental matrices. The method achieves high separation capacity, sensitive detection, and flexible ionization, paving the way for robust monitoring and future quantitative applications.

References

• Tomy, G.T. (2010). Analysis of Chlorinated Paraffins in Environmental Matrices: The Ultimate Challenge for the Analytical Chemist. In J. de Boer (Ed.), The Handbook of Environmental Chemistry: Chlorinated Paraffins, Vol. 10, pp. 83–106. Springer.