A Novel Solution to the Analysis of Highly Complex Environmental Samples

Importance of the topic

Environmental samples often contain complex matrices with a wide variety of analytes at trace to high concentrations. High-resolution, high-sensitivity methods are essential for reliable identification of known targets and structural elucidation of unknowns. Combining two-dimensional gas chromatography with high-resolution TOF-MS enhances chromatographic capacity and data quality for comprehensive environmental analysis.

Study objectives and overview

This study demonstrates a novel analytical workflow integrating comprehensive GC×GC with the Pegasus® GC-HRT+ high-resolution multi-reflecting TOF-MS using Encoded Frequent Pushing (EFP). Applications include pesticide residues in eggplant matrices and trace organic compounds in arctic ice samples. Key aims are to assess sensitivity, dynamic range, separation power, and spectral deconvolution of coeluting compounds.

Methodology and instrumentation

The Pegasus GC-HRT+ employs a 20 m Folded Flight Path for resolving power > 25 000 and sub-ppm mass accuracy at acquisition rates up to 200 spectra/s. Encoded Frequent Pushing multiplexing increases duty cycle and sensitivity while minimizing spectral overlap. GC×GC separations use comprehensive two-dimensional columns to boost peak capacity. Experiments included OFN standards for sensitivity and IDL evaluation, a 107-pesticide calibration series in eggplant extract (0.5–20 ppb), and arctic ice sample analyses in 1D and 2D modes with/without EFP.

Main results and discussion

– OFN experiments achieved an IDL of 0.04 ppb, demonstrating five orders of magnitude dynamic range and significant sensitivity gains with EFP.
– Eggplant pesticide analysis at 10 ppb showed clear TIC and quantitation AIC traces. Deconvoluted spectra of α-BHC and Tefluthrine at 10 ppb yielded high similarity scores (894, 929).
– GC×GC contour plots of a 2.5 ppb eggplant standard revealed improved separation of complex matrix components. Zoomed regions highlighted coeluting analytes resolved in two dimensions.
– Arctic ice samples analyzed in 1D and 2D with EFP demonstrated enhanced peak detection and library match confidence. Peak finding improved significantly when combining GC×GC with EFP.

Benefits and practical applications

• Enhanced sensitivity and dynamic range for trace-level detection.
• Improved chromatographic peak capacity for complex sample matrices.
• Robust spectral deconvolution of coeluting analytes.
• Increased confidence in compound identification with sub-ppm mass accuracy.
• Applicability to environmental monitoring, pesticide residue testing, QA/QC, and retrospective data analysis.

Future trends and applications

Further integration of GC×GC–HRMS with automated data processing and non-targeted screening will expand applications in metabolomics, petrochemical analysis, and forensic investigations. Advances in retrospective data mining and machine-learning algorithms are expected to leverage full-range high-resolution data for novel compound discovery and environmental exposure assessment.

Conclusion

The combination of Encoded Frequent Pushing multiplexing with a multi-reflecting high-resolution TOF-MS and comprehensive GC×GC offers a powerful platform for analyzing highly complex environmental samples. It delivers exceptional sensitivity, mass accuracy, and separation power, meeting current and future analytical challenges.

References

• ASMS 2015 Proceedings, P. Willis et al. High Resolution Multi-Reflecting TOFMS with Multiplexing by Encoded Frequent Pulsing, TOA am.
• Technical Brief: Encoded Frequent Pushing 209-066-018, LECO Corporation.