Analysis of Short Chain Chlorinated Paraffins (SCCPs) by GC -Q/ TOF using Complimentary and Novel Ionization

Significance of the Topic

The analysis of Short Chain Chlorinated Paraffins (SCCPs) is crucial due to their persistence, bioaccumulation and widespread industrial applications in lubricants, coolants and flame retardants. High-resolution mass spectrometry methods are essential for reliable detection and quantification of SCCPs in complex environmental and industrial matrices, addressing their potential health and ecological impacts.

Objectives and Study Overview

This study evaluates two complementary acquisition modes of gas chromatography–quadrupole time-of-flight mass spectrometry (GC-Q/TOF) for SCCP analysis: negative chemical ionization (NCI) and low energy electron ionization (EI). The goal is to compare fragmentation behavior, sensitivity and quantitation accuracy for SCCP congeners with varying chlorine content.

Methodology and Instrumentation

The analytical approach combines GC separation with high-resolution accurate-mass detection under two ionization strategies:

• Negative Chemical Ionization (NCI) using methane as reagent gas
• Low Energy Electron Ionization (EI) at optimized 22 eV to reduce excessive fragmentation

Samples included standard SCCP mixtures (51 %, 55.5 %, 63 % chlorine) and an isotopically labeled internal standard (13C10-hexachlorodecane). Quantitation employed Agilent MassHunter software with calibration curves from available pure congeners and estimated responses for those lacking standards.

Main Results and Discussion

Under NCI, SCCP spectra showed minimal fragmentation, with prominent molecular ions [M]􏰁 and [M–HCl]􏰁 preserving the carbon backbone. Low energy EI at 22 eV produced increased fragmentation but significantly enhanced detection sensitivity for low-chlorine congeners (e.g., C10Cl4). Calibration based on pure standards quantified 71 %–93 % of mixture components directly, with the remainder estimated via calibration analogues. The two ionization modes offered complementary insights into congener profiles and quantitation performance.

Benefits and Practical Applications

• High-resolution NCI simplifies spectral interpretation by conserving molecular ions, improving identification in complex matrices.
• Low energy EI enhances sensitivity for congeners with low chlorine content, expanding quantitation coverage.
• Combining both modes yields comprehensive congener profiling, valuable for environmental monitoring, regulatory compliance and industrial quality control.

Future Trends and Potential Uses

Future developments may include further optimization of ionization energies, integration of advanced data deconvolution algorithms and extension to medium and long chain chlorinated paraffins. Combining GC-Q/TOF with tandem MS or alternative reagent gases could improve isomer differentiation and trace-level quantitation. Automation and miniaturization may enable on-site SCCP screening.

Conclusion

The dual application of NCI and low energy EI on a high-resolution GC-Q/TOF platform provides a sensitive and selective strategy for SCCP analysis. This complementary approach enhances congener coverage and quantitation reliability, supporting environmental assessment and industrial QC efforts.

Instrumentation Used

Agilent 7890B GC with interchangeable CI source and low-energy EI source; Agilent 7250 high-resolution Q-TOF MS; Methane reagent gas for NCI; Agilent MassHunter Quantitative Analysis 10 software.

References

1. Persistent Organic Pollutants Review Committee. Short-chained chlorinated paraffins: Risk Profile. UNEP/POPS/POPRC.2, 2017.
2. Chlorinated Paraffins Industry Association. Chlorinated Paraffins: A Status Report, 2009.
3. Zencak Z. et al. Evaluation of Four Mass Spectrometric Methods for the Gas Chromatographic Analysis of Polychlorinated n-Alkanes. J. Chromatogr. A 1067, 295–301 (2004).
4. Gao W. et al. Quantification of Short- and Medium-Chain Chlorinated Paraffins in Environmental Samples by GC-Q/TOF MS. J. Chromatogr. A 1452, 98–106 (2016).