CONFIRMATION OF DIOXINS AND DIOXIN-LIKE SUBSTANCES AT SUB-FEMTOGRAM LEVELS USINGATMOSPHERIC PRESSURE GAS CHROMATOGRAPHY (APGC) MS/MS

Significance of the Topic

The detection of polychlorinated dibenzo-p-dioxins (PCDDs) and dibenzofurans (PCDFs) at ultra-trace levels is critical due to their persistence, bioaccumulation and toxicity.
International regulations under the Stockholm Convention and food safety directives mandate precise monitoring in environmental and food matrices.

Objectives and Study Overview

This study evaluated the sensitivity and robustness of atmospheric pressure gas chromatography (APGC) coupled with Xevo TQ-XS tandem quadrupole mass spectrometry for sub-femtogram quantification of dioxins.
The work aimed to determine detection limits using solvent standards and to confirm accurate quantitation in a complex fly ash QC sample.

Methodology

Two GC methods were applied:

• TCDD assessment: Agilent DB-5MS (30 m×0.25 mm×0.25 µm), He at 1.0 mL/min; injection at 290 °C (pulsed splitless 32 psi, 0.5 min); oven 130 °C (1.2 min) to 320 °C at 20 °C/min.
• PCDD/PCDF assessment: Zebron ZB-5MS (60 m×0.25 mm×0.25 µm), He at 1.0 mL/min; injection at 290 °C (pulsed splitless 50 psi, 1.8 min); oven 130 °C (1.8 min) through multi-ramp to 320 °C.

The MS operated with an APGC source (2.0 µA corona pin), cone gas 250 L/hr, auxiliary gas 200 L/hr, makeup gas 300 mL/min, and two MRM transitions for confirmation.

Used Instrumentation

• Atmospheric Pressure Gas Chromatography (APGC)
• Waters Xevo TQ-XS Tandem Quadrupole MS
• Agilent DB-5MS GC Column
• Zebron ZB-5MS GC Column

Results and Discussion

Sub-femtogram sensitivity was demonstrated for 2,3,7,8-TCDD with on-column S/N of 5.7 at 100 ag and 20.7 at 250 ag.
The method exhibited excellent linearity (R²=0.998) from 100 ag to 100 pg.
Over 20 days and 1000 injections, a 100 fg standard showed RSD of 9.2% and stable isotope ratios (<15% variation).
Analysis of a QC fly ash sample yielded quantitation consistent with certified values, confirming applicability to complex matrices.

Benefits and Practical Applications

• Reduced need for standard preconcentration through high sensitivity
• Lower consumption of costly isotope-labelled standards
• Minimal sample requirements and simplified workflow
• High robustness with thousands of injections without performance loss
• Compliance with EU and EPA dioxin analysis regulations

Future Trends and Potential Applications

Advancements may include further lowering detection limits via optimized ion sources and detector designs.
Integration with high-resolution MS and automated sample preparation could enhance throughput.
Extension of APGC-MS/MS to dioxin-like PCBs and other persistent organic pollutants is anticipated.
Development of portable APGC systems may enable on-site screening.

Conclusion

APGC coupled with the Xevo TQ-XS achieves sub-femtogram quantification of PCDD/PCDFs in complex samples, offering a sensitive, robust and regulation-compliant alternative to magnetic sector GC-MS.

References

1. United Nations Treaty: Stockholm Convention of Persistent Organic Pollutants, 2001.
2. Dunstan J., Hall K., Jones R. et al., A Confirmatory Method for PCDDs and PCDFs in Compliance with EU Regulation 589/2014/EU Using APGC with Xevo TQ-S, Waters Application Note 720005431en, 2015.
3. EN 16215:2012 European Standard, European Committee for Standardization, 2012.
4. EU Commission Regulation 589/2014, Methods for sampling and analysis of dioxins and PCBs in foodstuffs, 2014.
5. EPA Method 1613 (Revision B), U.S. Environmental Protection Agency, Washington, DC, 1994.