A comparison of GC/MS-MS using the Agilent 7000 GC-QQQ and GC/HRMS for the trace level analysis of Dioxins in Environmental Samples

Importance of the Topic

The determination of polychlorinated dibenzo-p-dioxins (PCDDs) and dibenzofurans (PCDFs) at trace levels in environmental matrices is critical for human health and ecological protection. Regulatory guidelines require measurement in the part-per-trillion range, demanding highly sensitive, selective, and cost-effective analytical methods. Screening techniques can expand monitoring capabilities to more laboratories and support rapid decision making.

Objectives and Study Overview

This study critically compares two analytical platforms for trace dioxin analysis in environmental samples:

• Agilent 7000 Triple Quadrupole GC/MS-MS
• Conventional high-resolution GC/HRMS

Twenty-two soil samples and five waste incinerator stack emission samples were analyzed by both methods. Results were assessed for sensitivity, selectivity, quantitation accuracy, and regulatory compliance.

Methodology and Instrumentation

Sample Preparation:

• Soil (10–30 g) was dried, spiked with 13C12-labelled 2,3,7,8-PCDD/F surrogates, extracted with organic solvents, and purified per EPA Method 1613.
• Stack emissions sampled and purified following EN 1948 protocols.
• Isotopic dilution quantitation; LOD based on S/N = 3; results expressed as WHO-TEQ (pg TEQ/g or fg/m³) using TEFs and middle-bound approach for values below LOD.

Applied Instrumentation

• GC/MS-MS: Agilent 7890 GC coupled to 7000 Triple Quadrupole MS in EI+ MRM mode; source/transfer at 280 °C.
• GC/HRMS: High-resolution MS per EPA 1613 and EN 1948 in EI+ SIM mode with resolving power > 10 000; monitored M+/M+2 and M+2/M+4 ions.
• Chromatography: 60 m × 0.25 mm × 0.25 µm 5% phenyl column; splitless injection; oven 160 °C (1 min), ramp 2.5 °C/min to 300 °C (6 min).

Main Results and Discussion

Instrumental Sensitivity and Selectivity:

• Standard injections (50–5000 fg) yielded S/N > 3 for all congeners on GC/MS-MS.
• Chromatograms of urban air samples (46 fg/m³ TEQ) showed comparable peak profiles on both platforms.

Soil Sample Results:

• TEQ range 0.33–14.11 pg WHO-TEQ/g; only one sample exceeded 10 pg/g residential limit.
• GC/MS-MS TEQs were slightly higher due to elevated LODs and middle-bound calculation.
• Correlation of total soil TEQs: R² ≈ 0.97; individual congeners: R² ≈ 0.99 over six orders of magnitude.
• Relative difference |±Δ%| averaged 61% for < 1 pg/g, and 4% for ≥ 1 pg/g, indicating reliable quantitation above 1 pg/g.

Air Emission Results:

• Individual congener correlations between methods yielded R² ≈ 0.98; some overestimations by GC/MS-MS but never underestimations.
• Performance meets Italy’s 0.1 ng/m³ TEQ limit for municipal waste incinerator emissions.

Benefits and Practical Applications

• GC/MS-MS screening offers rapid, cost-effective detection of PCDD/Fs in soils and air emissions.
• Enables more laboratories to perform regulatory screening without high-resolution MS investment.
• Supports environmental monitoring programs and industrial compliance checks.

Future Trends and Opportunities

• Advances in triple quadrupole sensitivity and lower detection limits may extend applicability to even lower TEQ levels.
• Integration of automated sample prep and data processing will streamline high-throughput analysis.
• Potential use of machine learning for improved deconvolution of coeluting congeners.
• Extension of GC/MS-MS screening to food, feed, and complex environmental matrices.

Conclusion

This comparative study demonstrates that the Agilent 7000 GC/MS-MS platform provides sensitivity, selectivity, and quantitative performance comparable to GC/HRMS for environmental PCDD/F analysis above 1 pg WHO-TEQ/g in soil and regulated air emissions. GC/MS-MS methods are thus suitable as reliable screening tools, broadening analytical capacity for dioxin monitoring.

References

• USEPA Method 1613: Tetra-through Octa-Chlorinated Dioxins and Furans by Isotope Dilution HRGC/HRMS, 1994.
• EC Regulation 1883/2006: Sampling and analysis methods for dioxins in foodstuffs, 2006.
• EC Regulation 152/2009: Methods of sampling and analysis for feed, 2009.
• Van den Berg M. et al., Toxicological Sciences, 93(2), 223–241, 2006.
• Lohmann R., Jones K.C., Science of the Total Environment, 219(1), 53–81, 1998.
• Italian D.Lgs. 152/2006: Environmental regulations for dioxins in soils and emissions.