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

Importance of the Topic

Polychlorinated dibenzo-dioxins (PCDDs) and dibenzofurans (PCDFs) are highly toxic persistent organic pollutants regulated under the Stockholm Convention. Their bioaccumulative behavior demands ultra-trace analysis in food and environmental matrices. Traditional high-resolution magnetic sector GC-MS methods require expert operation and extensive sample preconcentration. The development of user-friendly, highly sensitive techniques is critical to ensure reliable monitoring at sub-femtogram levels.

Objectives and Study Overview

This study aimed to establish detection limits for PCDDs and PCDFs in solvent standards and to confirm accurate quantitation in a complex QC fly ash sample. Utilizing Atmospheric Pressure Gas Chromatography (APGC) coupled with a Xevo TQ-XS tandem quadrupole mass spectrometer, the work evaluated sensitivity, linearity, reproducibility, isotope ratio stability, and real-sample performance against regulatory requirements.

Methodology and Instrumentation

The analytical setup consisted of two GC methods and a single APGC-MS/MS configuration:

• GC columns and programs:
  
  • PCDD assessment: Agilent DB-5MS, 30 m×0.25 mm×0.25 µm; He 1.0 mL/min; pulsed splitless injection; ramp from 130 °C to 320 °C at 20 °C/min.
  • PCDD/PCDF assessment: Zebron ZB-5MS, 60 m×0.25 mm×0.25 µm; He 1.0 mL/min; splitless injection; multi-step ramp from 130 °C to 320 °C.
• APGC-MS/MS parameters:
  
  • Corona pin current 2.0 µA; cone gas 250 L/hr; auxiliary gas 200 L/hr; makeup gas 300 mL/min.
  • MRM transitions selected for confirmatory detection of 2,3,7,8-TCDD and congeners.

Key Findings and Discussion

• Sensitivity: Sub-femtogram detection of 2,3,7,8-TCDD achieved a signal-to-noise ratio of 5.7 at 100 ag on-column and 20.7 at 250 ag.
• Linearity: Calibration over 100 ag to 100 pg on-column yielded R2 of 0.998.
• Reproducibility: Injection of 100 fg standard across 20 days showed RSD of 9.2% over 1000 injections without isotopic correction.
• Isotope Ratio Stability: Consistent isotope ratios (<15% deviation) across calibration standards demonstrate reliable confirmatory performance.
• Complex Matrix Analysis: QC fly ash sample quantitation matched certified values, illustrating robustness in challenging matrices.

Benefits and Practical Applications

• Sub-femtogram sensitivity allows dilution of expensive standards and reduces preconcentration steps.
• High throughput capability with minimal sample requirement and reduced analysis cost.
• Robust performance over thousands of injections ensures reproducible data for regulatory compliance.

Future Trends and Potential Applications

• Extension of APGC-MS/MS to multi-class contaminant screening in food, water, and soil.
• Integration of automated sample introduction and data processing for higher throughput labs.
• Adaptation to novel environmental pollutants requiring ultra-trace detection.

Conclusion

APGC coupled with the Xevo TQ-XS mass spectrometer offers a robust, highly sensitive platform for confirmatory analysis of dioxins and furans at sub-femtogram levels. This approach exceeds current regulatory demands while reducing sample preparation time and resource consumption.

Reference

1. United Nations Treaty: Stockholm Convention on Persistent Organic Pollutants, 2001.
2. Dunstan J 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 No. 720005431en, 2015.
3. EN 16215:2012 European Standard for determination of PCDDs and PCDFs, CEN, 2012.
4. EU Commission Regulation 589/2014 on dioxins, furans and PCBs in foodstuffs.
5. EPA Method 1613 (Revision B), US EPA, 1994.