Enhancing of a Powerful Discovery Tool with a Novel Multi-Mode Ion Source

Significance of the Topic

In modern analytical chemistry, characterization of complex mixtures demands combining high resolving power with versatile ionization. The introduction of a Multi-Mode Ion Source (MMS) on a GC-HRT+ platform enhances molecular identification by providing complementary electron ionization (EI), positive chemical ionization (PCI) and electron capture negative ionization (ECNI) data in a single run.

Study Objectives and Overview

This application note evaluates the performance of the Pegasus GC-HRT+ equipped with MMS by analyzing a mixture of EPA 8270 MegaMix and Method 525.3 organochlorine pesticide standards. The goal is to demonstrate improved sensitivity, mass accuracy, and spectral fidelity across ionization modes for robust compound identification.

Methodology and Instrumentation

Samples were prepared by diluting combined EPA 8270 and 525.3 OCP standards to 2 ng/µL in dichloromethane. Analysis employed an Agilent 7890B GC with an Rxi-5ms column (30 m × 0.25 mm ID × 0.25 µm), splitless injection at 250 °C, and a temperature gradient from 40 °C to 300 °C at 10 °C/min. Helium carrier gas flowed at 1.0 mL/min. The Pegasus GC-HRT+ mass spectrometer recorded data at 12 Hz across m/z ranges adapted to each mode (EI 45–1000, PCI 60–1000 with CH4 reagent, ECNI 30–1000 with CH4 reagent).

Main Results and Discussion

EI provided established fragmentation patterns and high library match scores but lacked molecular ions for some analytes. PCI generated protonated and alkyl adducts with mass errors <1 ppm and isotopic fidelity >950/1000, enabling formula confirmation for compounds missing EI molecular peaks. ECNI yielded intense molecular anions with minimal fragmentation, especially for electron-deficient and halogenated species, with isotopic fidelity up to 990/1000. Combining EI and ECNI drove confident identification of polyhalogenated pesticides such as endosulfan sulfate, chlordane, and α-endosulfan, achieving mass errors below 1 ppm and enhanced selectivity.

Benefits and Practical Applications

• Comprehensive profiling through three ionization modalities without source change.
• High mass accuracy and isotopic fidelity for molecular and fragment ions.
• Improved detection of labile or electron-rich/deficient analytes.
• Streamlined workflows for environmental, forensic, metabolomic, food and flavor, and industrial quality control analyses.

Future Trends and Applications

Integration of MMS-enabled GC-HRT+ with multidimensional separations and non-targeted screening workflows will expand discovery capabilities. Advances in software for automated spectral deconvolution and library building, alongside alternative reagent gases and ionization strategies, promise further gains in sensitivity, selectivity, and throughput.

Conclusion

The Pegasus GC-HRT+ with MMS offers a unique, flexible platform for in-depth analysis of complex samples. By combining EI, PCI, and ECNI in a single source, it delivers high-resolution, accurate mass spectra that enhance compound identification and quantification across diverse analytical challenges.

References

1. Anstett A., Fanny C., Alonso D.E., Waddell Smith R. Characterization of 2C-phenethylamines using high-resolution mass spectrometry and Kendrick mass defect filters. Forensic Chemistry 2018;7:47–55.
2. Dubois L.M., Pierre-Hugues S., Heudt L., Focant J.F., Perrault K.A. Characterizing decomposition odor from soil and adipocere samples using HS-SPME-GCxGC-HRTOFMS. Forensic Chemistry 2018;8:11–20.
3. Veenaas C., Ripszam M., Glas B., Liljelind I., Claeson A.S., Haglund P. Differences in chemical composition of indoor air related to building symptoms. Science of the Total Environment 2020;761:137444.
4. Mazur D.M., Detenchuk E.A., Sosnova A.A., Artaev V.B., Lebedev A.T. GC-HRMS with complementary ionization techniques for target and non-target screening of air pollution markers in Moscow snow. Science of the Total Environment 2021;761:144506.
5. Lebedev A.T., Mazur D.M., Artaev V.B., Tikhonov G.Y. Better screening of non-target pollutants in complex samples using advanced chromatographic and mass spectrometric techniques. Environmental Chemistry Letters 2020;18:1753–1760.
6. Daygon V.D., Calingacion M., Forster L.C., De Voss J.J., Schwartz B.D., Ovenden B., Alonso D.E., McCouch S.R., Garson M.J., Fitzgerald M.A. Metabolomics and genomics combine to unravel the pathway for fragrance in rice. Scientific Reports 2017;8:8767.
7. Di Giovanni N., Meuwis M.A., Louis E., Focant J.F. Untargeted serum metabolic profiling by comprehensive two-dimensional gas chromatography-high-resolution time-of-flight mass spectrometry. Journal of Proteome Research 2020;19(3):1013–1028.
8. Ncube S., Dube S., Nindi M.M. Determination of volatile compounds during deterioration of African opaque beer using stir bar sorptive extraction and GC-HRMS. Current Research in Food Science 2020;3:256–267.
9. Vyviurska O., Spanik I. Assessment of Tokaj varietal wines with comprehensive two-dimensional gas chromatography coupled to high-resolution mass spectrometry. Microchemical Journal 2020;152:104385.
10. Alisi I., Zoccali M., Tranchida P.Q., Mondello L. Analysis of organic compounds in coal tar by using comprehensive two-dimensional gas chromatography-high-resolution time-of-flight mass spectrometry. Separations 2020;7:26.
11. Gross J.H. Mass Spectrometry – A Textbook. Springer 2004, Chapter 7.