A Novel High-Resolution, Accurate-Mass, Orbitrap-Based GC-MS for Routine Analysis of Short Chained Chlorinated Paraffins

Significance of the topic

Short chained chlorinated paraffins (SCCPs) represent a class of halogenated chemicals widely used as lubricants, coolants, plasticizers and flame retardants. Their high persistence in the environment and tendency to bioaccumulate raise significant health and ecological concerns. Rigorous monitoring of SCCPs is essential due to their regulatory status under the Stockholm Convention and Europe’s restrictions on production and use. Analytical challenges stem from the compounds’ structural complexity, low environmental concentrations and extensive isomeric mixtures.

Objectives and overview

The study introduces a benchtop Orbitrap-based gas chromatography–mass spectrometry (GC-MS) platform designed to improve routine SCCP analysis. Main aims include:

• Quantify sensitivity and linearity across trace concentrations.
• Evaluate selectivity between complex isomeric and background ions.
• Assess precision and dynamic range.
• Compare electron ionization (EI) and negative chemical ionization (NCI) modes.

Methodology

Two technical mixtures of SCCPs (63% and 55.5% chlorine) were prepared in cyclohexane in concentrations ranging from 1 to 10,000 pg/µL. Method performance was tested using full-scan acquisition at 60,000 resolving power (FWHM at m/z 200). Analytical metrics evaluated included instrumental detection limits (IDLs), linear dynamic range, mass accuracy and repeatability. Selectivity tests involved spiking SCCP standards with polychlorinated biphenyls to simulate interferences at low mass differences.

Used Instrumentation

• Thermo Scientific TRACE 1310 GC with splitless injector and temperature program.
• Exactive GC Orbitrap mass spectrometer operating at 60k resolving power in EI and NCI modes.
• TriPlus RSH autosampler for automated injections.
• TraceFinder software for lockmass correction and data processing.

Main results and discussion

• IDLs in EI were around 10 pg/µL for total homologues and as low as 3 pg/µL in NCI for individual groups.
• Excellent linearity (R2 > 0.999) observed across 1–10,000 pg/µL in both ionization modes.
• Sub-ppm mass accuracy achieved at high and low concentrations provided sufficient selectivity to discriminate SCCP-specific ions from matrix or higher-mass interferences.
• Resolving powers above 30k were necessary to resolve target SCCP ions (e.g., m/z 253.03121) from close PCB interferences (m/z 253.01733).
• Repeatability tests showed relative standard deviations below 5% for selected congeners at 25 pg/µL.

Benefits and practical applications

The Orbitrap-based GC-MS approach simplifies routine monitoring of SCCPs by combining high resolution, accurate mass measurements and straightforward instrument setup. It enables robust quantification of individual homologues in complex environmental matrices, supports regulatory compliance and improves confidence in trace-level analyses.

Future trends and prospects

• Integration with automated sample preparation to boost throughput.
• Application to other persistent organic pollutants requiring high selectivity.
• Development of standardized protocols using accurate-mass full-scan workflows.
• Enhanced data processing algorithms leveraging high-resolution spectral libraries.

Conclusion

The Exactive GC system delivers sub-ppm mass accuracy, high sensitivity and excellent selectivity for SCCP analysis. Performance in both EI and NCI modes meets the stringent demands of environmental monitoring, offering a powerful tool for routine trace analysis of complex halogenated mixtures.

Reference

• Geng N. et al. Environ Sci Technol, 2015, 49(5), 3076–83. doi:10.1021/es505802x.
• European Commission. Commission Regulation (EU) No 519, Off. J. Eur. Union, L159, 1–4, 2012.