Mass resolving power of 240,000: for confident compound identification

Importance of the Topic

Analytical laboratories require ultra-high resolution mass spectrometry to confidently identify known and unknown compounds in complex matrices. The Orbitrap Exploris GC 240 system offers a resolving power of 240 000 and sub-ppm mass accuracy, addressing challenges in targeted screening, untargeted profiling, and structural elucidation.

Study Objectives and Overview

The primary goal was to demonstrate the analytical performance of the Thermo Scientific Orbitrap Exploris GC 240 in GC–MS applications. Key aims included evaluating mass resolution, sensitivity retention at high resolution, reliable compound identification workflows, and structural confirmation strategies in complex matrices such as soil extracts.

Methodology and Instrumentation

Data were acquired in electron ionization (EI) full-scan mode across resolving powers from 15 000 to 240 000 (FWHM at m/z 200). Targeted analyses used narrow mass extraction windows (±5 ppm) to improve selectivity. Unknown screening combined EI full scan, spectral deconvolution with library search, and formula generation using accurate mass and isotopic patterns. Confirmation steps employed positive chemical ionization (PCI) with methane/ammonia reagent gas and MS/MS in the HCD cell.

• Orbitrap Exploris GC 240 benchtop mass spectrometer
• Thermo Scientific TriPlus RSH autosampler
• Methane (10% ammonia) reagent gas for PCI

Main Results and Discussion

• Resolution and Selectivity: At 240 000 RP, bifenthrin (m/z 167.08113) was resolved from matrix interference, avoiding false negatives. A minimum of 60 000 RP was required for reliable separation.
• Sensitivity Retention: Peak areas for pyriproxyfen (100 ng/mL) remained consistent across 15 000 to 240 000 RP, demonstrating no loss in sensitivity at the highest resolution.
• Unknown Identification: Formula generation for an unknown ion (m/z 424.33375) at 60 000 RP yielded three candidates at 1 ppm tolerance. Isotopic pattern matching confirmed C29H44O2 (α-tocotrienol).
• Spectral Fidelity: Pentachlorobenzonitrile in soil extract showed sub-ppm mass accuracy (<1 ppm) for all isotopic peaks at 240 000 RP, ensuring high confidence in identification.
• Molecular Ion Confirmation: PCI enabled observation of the quasimolecular [M+H]+ ion for triadimefon with <1 ppm mass error. Subsequent PCI MS/MS provided fragment ions supporting structural assignment.

Benefits and Practical Applications

The Orbitrap Exploris GC 240 delivers unprecedented resolution and mass accuracy without sacrificing sensitivity. This performance supports:

• Targeted screening with low false negative rates
• Untargeted profiling and retrospective data mining
• Robust structural elucidation workflows
• High-throughput QA/QC and environmental analyses

Future Trends and Opportunities

Emerging applications include metabolomics and lipidomics in complex biological matrices, AI-driven data analysis for automated annotation, and integration with high-throughput workflows. Continued advances in informatics and mass spectrometric hardware will expand the scope of discovery and quantitative science.

Conclusion

The Thermo Scientific Orbitrap Exploris GC 240 mass spectrometer, with 240 000 resolving power and sub-ppm mass accuracy, offers unmatched selectivity, sensitivity, and confidence for both targeted and discovery GC–MS workflows. Its combination of high resolution, robust sensitivity, and advanced ionization methods enables comprehensive compound identification and structural elucidation in complex matrices.

References

1. Cooper J, Roberts D, Cojocariu C. Mass resolving power of 240 000 for confident compound identification. Thermo Fisher Scientific Application Note 10730. 2020.
2. Thermo Fisher Scientific. Simple and rapid screening of melamine in milk products with high-resolution accurate mass Orbitrap LC–MS. Application Note 502. 2009.
3. Thermo Fisher Scientific. Metabolomics of C. elegans via isotopic ratio outlier analysis using high-resolution accurate-mass LC–MS/MS. Application Note 592. 2019.