A New Approach to the Analysis of Chlorinated Paraffins by Gas Chromatography Quadrupole Time‑of-Flight Mass Spectrometry

Importance of the Topic

Chlorinated paraffins (CPs) are widely used industrial mixtures classified by chain length into short-chain (C10–C13), medium-chain (C14–C17), and long-chain (C>17) compounds. Due to their environmental persistence, toxic potential, and complex congener distributions, accurate analysis of CPs is essential for environmental monitoring, regulatory compliance, and risk assessment.

Objectives and Study Overview

This study aimed to develop and validate a single-injection analytical approach for simultaneous quantification of short-chain CPs (SCCPs) and medium-chain CPs (MCCPs) in diverse matrices. Gas chromatography coupled to quadrupole time-of-flight high-resolution mass spectrometry in negative chemical ionization mode (GC-NCI-Q-TOF-HRMS) was employed, leveraging accurate mass extraction and a chlorination response factor model to assess total CP levels and congener distributions.

Methodology and Instrumentation

Sample preparation covered industrial products, food items, and passive air (XAD) samplers. Accelerated solvent extraction followed by florisil/silica cleanup and fractionation provided CP-enriched extracts. GC conditions included an Agilent 7890B with HP-5MS UI column and a temperature gradient from 100 °C to 310 °C. The Agilent 7200 GC-Q-TOF operated in NCI with a mass range of m/z 50–600, source and quadrupole at 150 °C, and resolution above 12 000. Auto-integration of extracted [M–Cl]– ions and a linear response factor versus chlorine content model enabled congener group quantification.

Main Results and Discussion

• Detection limits for SCCPs and MCCPs ranged from 24–81 ng/mL and 27–170 ng/mL, respectively.
• Linearity spanned three orders of magnitude (0.25–100 ng/µL) with R²≥0.99 for mixed chlorination standards.
• Accuracy for single standards was 86–124% (SCCPs) and 114–129% (MCCPs); inter-day RSDs were <4% for SCCPs and <13% for MCCPs.
• High-resolution (≥12 000) resolved isobaric interferences between congener ions and eliminated matrix overlap, enabling clean extracted ion chromatograms at ±50 ppm tolerance.
• Comparison with low-resolution GC-NCI-LRMS showed improved selectivity, reduced self-interference, single-run SIM acquisition versus four separate runs, and more accurate congener distributions in food, air, and technical product samples.

Practical Applications and Benefits of the Method

This GC-NCI-Q-TOF-HRMS approach delivers reliable CP quantification in environmental, food, and industrial samples. Its high throughput and single-injection capability support routine monitoring, regulatory compliance checks, quality assurance in production, and detailed congener profiling for exposure and fate studies.

Future Trends and Opportunities

• Synthesis of diverse chlorination reference standards to refine response factor models.
• Extension to long-chain CPs and emerging uses of ultra-high-resolution mass spectrometers.
• Integration with automated data processing and machine learning for rapid congener identification.
• Large-scale environmental surveys and global monitoring networks leveraging standardized HRMS protocols.

Conclusion

The developed GC-NCI-Q-TOF-HRMS method achieves sensitive, accurate, and selective measurement of SCCPs and MCCPs in a single run. Its enhanced resolution and streamlined workflow represent a significant advance over low-resolution approaches, enabling robust environmental and industrial analyses of chlorinated paraffins.

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