Tetra- Through Octa-Chlorinated Dioxins and Furans Analysis in Water by Isotope Dilution GC/MS/MS

Significance of the Topic

Polychlorinated dibenzo-p-dioxins and dibenzofurans (CDDs/CDFs) are highly toxic environmental contaminants formed as byproducts of industrial and combustion processes. Their persistence, bioaccumulation potential, and adverse health effects at ultra-trace concentrations drive stringent regulatory monitoring in water, food, and soil. Robust analytical methods are essential to ensure public safety, compliance with environmental norms, and informed risk assessment.

Objectives and Overview of the Study

This study evaluates the capability of triple quadrupole gas chromatography tandem mass spectrometry (GC/MS/MS) to meet the U.S. EPA Method 1613B performance criteria for the analysis of tetra- through octa-chlorinated dioxins and furans in water. By comparing GC/MS/MS results to those obtained with high-resolution magnetic sector GC/HRMS, the work aims to demonstrate compliance with regulatory requirements while reducing instrument cost, maintenance burden, and operational complexity.

Methodology

Sample Preparation and Cleanup

• One liter of water is filtered, and both filter paper and filtrate undergo Soxhlet and liquid–liquid extraction, respectively.
• Combined extracts are purified via sequential silica, alumina, florisil, or carbon column cleanup.
• 13C-labeled internal standards, cleanup standards, and injection standards are introduced at defined steps to support isotope dilution quantification and quality control.

GC/MS/MS Analysis

• Agilent 7890B GC fitted with a DB-5ms Ultra Inert column (60 m × 250 µm × 0.25 µm).
• Agilent 7010 Triple Quadrupole MS operated in pulsed splitless mode with helium quench and nitrogen collision gases.
• Method 1613B retention time windows defined by a mixture of window-defining compounds.
• Multiple reaction monitoring (MRM) transitions and collision energies adapted from validated Agilent Food and Feed methods to target all 17 toxic congeners.
• Key quality criteria assessed include isomer specificity (valley height < 25 %), relative retention time (RRT), ion abundance ratios (± 15 % of theoretical), and signal-to-noise ratio (S/N ≥10 for standards, ≥ 2.5 in samples).

Used Instrumentation

• Agilent 7890B gas chromatograph with multimode inlet.
• Agilent J&W DB-5ms Ultra Inert GC column.
• Agilent 7010 Triple Quadrupole mass spectrometer.
• Soxhlet extraction apparatus, liquid–liquid extraction glassware.
• Silica, alumina, florisil, and carbon cleanup columns.

Main Results and Discussion

Isomer Separation and Specificity

• All congeners eluted within defined windows; <25 % valley achieved for toxic 2,3,7,8-TCDD/TCDF and most isomers.
• Partial coelution observed for 1,2,3,7,8,9-HxCDF vs 1,2,3,4,8,9-HxCDF, consistent with HRMS data; quantification via estimated maximum peak concentration.

Retention Time and Ion Ratios

• RRT values for all analytes fell within Method 1613B tolerances (0.999–1.002).
• Ion abundance ratios remained within ± 15 % of theoretical values.

Calibration and Sensitivity

• Isotope-dilution calibration over 0.2–2 500 ng/mL yielded RF differences < 15 % and RF RSD < 10 %.
• S/N exceeded 10 for all calibration points; verification standard recoveries within 70 – 130 %.
• Initial precision and recovery tests demonstrated consistent recoveries and precision for native and labeled congeners at method levels.

Comparison to GC/HRMS

• Analysis of spiked water samples showed excellent correlation (r2 > 0.99) between GC/MS/MS and GC/HRMS quantification down to pg/mL levels.

Benefits and Practical Applications

GC/MS/MS offers a cost-effective, lower-maintenance alternative to high-resolution sector instruments, with simplified operation and reduced specialist training requirements. It fulfills Method 1613B criteria for isomer specificity, sensitivity, and accuracy, enabling routine monitoring of dioxins and furans in environmental laboratories, water utilities, and food safety testing.

Future Trends and Applications

Advancements in MRM optimization and alternative stationary phases may further improve isomer resolution, particularly for challenging hexachlorinated isomers. Integration with automated sample preparation platforms and high-throughput workflows could broaden application to complex matrices such as soils, sediments, and biological tissues. Ongoing regulatory acceptance of GC/MS/MS for dioxin analysis will expand access to robust monitoring and enforcement programs globally.

Conclusion

This study demonstrates that triple quadrupole GC/MS/MS can reliably determine tetra- through octa-chlorinated dioxins and furans in water according to EPA Method 1613B performance requirements. Comparable sensitivity, specificity, and quantitation accuracy to GC/HRMS were achieved, validating GC/MS/MS as a practical, cost-effective tool for environmental dioxin monitoring.

References

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