Quantitative Determination of Dioxins in Drinking Water by Isotope Dilution using Triple Quadrupole GC-MS/MS

Significance of the Topic

Dioxins (PCDDs and PCDFs) are highly toxic and persistent organic pollutants regulated worldwide due to their adverse effects on human health and the environment. Monitoring trace levels in drinking and recreational water is essential for regulatory compliance and public safety. Traditional high‐resolution mass spectrometry methods offer excellent sensitivity but incur high costs and complex maintenance. A triple quadrupole GC-MS/MS approach provides a cost-effective, user-friendly alternative for routine quantification of dioxins in water matrices.

Objectives and Study Overview

This study aimed to develop and validate an isotope-dilution GC-MS/MS method for the quantitative determination of seventeen dioxin congeners in water, following the principles of EPA Method 1613 but employing a triple quadrupole detector. Validation covered calibration performance, detection limits, precision, accuracy, and practical application to local tap water, bottled mineral water, and swimming pool water.

Used Instrumentation

• GC-MS/MS System: Shimadzu GCMS-TQ8040 triple quadrupole
• Autosampler: AOC-20i in splitless injection mode
• Column: SH-Rxi-5Sil MS (60 m × 0.25 mm ID × 0.25 µm film)
• Carrier Gas: Helium at constant linear velocity (29.4 cm/s)
• Ionization: Electron impact at 70 eV; ion source 230 °C; interface 280 °C
• MRM Transitions: Individually optimized with programmed detector voltage to enhance sensitivity in critical elution windows

Methodology

Water samples underwent liquid–liquid extraction as per EPA 1613, achieving a 50 000-fold concentration factor. Seventeen native congeners and 13C-labelled analogues were spiked for isotope-dilution calibration. Seven-level calibration curves exhibited repeatability below 10% RSD and correlation coefficients above 0.999. The validation workflow included calibration verification, ongoing precision and recovery checks, method blanks, and calculation of method detection limits (MDLs) following CFR guidelines.

Main Results and Discussion

Chromatographic separation achieved less than 1% peak overlap in the hexa-congener region. All analytes showed excellent linearity (R2 > 0.999) across their calibration ranges. The MDL for 2,3,7,8-TCDD was determined at 0.26 pg/L in water. Recovery at the MDL level averaged 61.7%, meeting acceptance criteria. Analysis of tap, bottled, and pool water detected no congeners above the minimum reporting levels.

Benefits and Practical Applications

The validated GC-MS/MS method parallels HRMS performance at reduced cost and operational complexity. It enables reliable, high‐throughput monitoring of trace dioxins in water, supporting routine environmental surveillance and regulatory compliance in public health laboratories.

Future Trends and Applications

Advances may include automated sample preparation, expansion to multi-class pollutant screening, and greener microextraction techniques. Increasing regulatory acceptance of tandem MS methods is likely to broaden their use across food, feed, and environmental analyses. Integration with high-resolution detectors may enable comprehensive non-targeted screening in the future.

Conclusion

A triple quadrupole GC-MS/MS method was successfully developed and validated according to EPA Method 1613 criteria. It offers robust sensitivity, precision, and accuracy for seventeen dioxin congeners in water, providing a cost-effective alternative for routine monitoring.

Reference

• Commission Regulation (EU) No. 589/2014
• US Environmental Protection Agency Method 1613
• 40 CFR Appendix B to Part 136
• Wisconsin Department of Natural Resources. Analytical Detection Limit Guidance, 1996