Short Chain Chlorinated Paraffins (SCCPs) analysis using negative chemical ionization (CI) and low energy EI by high-resolution GC/Q-TOF

Importance of the Topic

Short-chain chlorinated paraffins (SCCPs) are widely used flame retardants and metal-processing additives. Their persistence and bioaccumulation in the environment pose regulatory and health concerns, making accurate, selective analysis essential for environmental monitoring and industrial quality control.

Goals and Overview of the Study

This study assesses the performance of a high-resolution GC/Q-TOF system in both negative chemical ionization (NCI) and low-energy electron ionization (EI) modes for the analysis of SCCP congeners. Key objectives include evaluating fragmentation behavior, quantitation accuracy, and isomer separation across mixtures with varying chlorine contents.

Methodology and Instrumentation

• Instrument: Agilent 7890B GC coupled to 7250 GC/Q-TOF
• Column: DB-5MS UI (30 m × 0.25 mm ID × 0.25 µm film)
• Carrier gas: Helium at 1.2 mL/min constant flow
• Injection: 1 µL splitless at 280 °C
• Oven program: 40 °C (1 min), ramp 25 °C/min to 320 °C, hold 9.8 min
• MS settings: mass range 50–650 m/z, 5 Hz acquisition rate
• Ionization: NCI using methane (40 %), EI at 22 eV
• Data processing: Agilent MassHunter Quantitative and Qualitative Analysis v10

Key Results and Discussion

• NCI spectra displayed predominant molecular (M–) and dechlorinated (M–Cl and M–HCl) ions with minimal fragmentation of the carbon backbone.
• Extracted ion chromatograms (±20 ppm) provided clear resolution of SCCP isomers in mixtures containing 51.5 %, 55 %, and 63.5 % chlorine.
• Calibration with pure congener standards yielded linear responses in the low ppb range, demonstrating quantitation precision.
• Low-energy EI (22 eV) enhanced detection sensitivity for low-chlorinated congeners (e.g., C10Cl4), producing characteristic fragment ions that improved isomer identification confidence.
• Combining orthogonal ionization modes allowed comprehensive profiling of SCCPs with diverse chlorine content.

Benefits and Practical Applications

• High selectivity in NCI simplifies spectral interpretation and reduces matrix interferences.
• Low-energy EI extends sensitivity to congeners with lower chlorine substitutions.
• High-resolution accurate mass measurement enhances confidence in congener assignment.
• Applicable to environmental monitoring, regulatory compliance, and industrial quality assurance.

Future Trends and Opportunities

• Extension to mid- and long-chain chlorinated paraffin analysis for broader halogenated hydrocarbon coverage.
• Incorporation of machine learning–driven deconvolution for automated isomer identification.
• Targeted fragmentation workflows for detailed structural elucidation.
• Development of compact, field-deployable high-resolution MS systems for on-site screening.

Conclusion

The high-resolution GC/Q-TOF platform, when operated in both NCI and low-energy EI modes, provides a robust solution for selective and sensitive SCCP analysis. Orthogonal ionization strategies streamline spectral complexity and enhance detection across diverse chlorine contents, addressing critical environmental and industrial analytical challenges.