GC coupling to LC MS instruments

Importance of the Topic

Recent analytical challenges in both routine and research settings demand versatile ionization solutions that can bridge the divide between gas chromatography (GC) and liquid chromatography (LC) mass spectrometry. The need to detect a wide range of compounds—including volatile pesticides, nitrosamines, perchlorinated molecules and non-polar alkanes—often requires multiple dedicated ion sources or compromises in sensitivity and selectivity. SICRIT® (Soft Ionization by Chemical Reaction In Transfer) offers an ambient-pressure, soft ionization interface that merges the analytical strengths of GC and LC-MS, simplifying workflows, minimizing sample preparation, and enhancing detection across diverse analyte classes.

Objectives and Study Overview

• To evaluate SICRIT® coupling with GC-MS and high-resolution MS platforms for both targeted and non-targeted analyses.
• To demonstrate enhanced sensitivity, expanded ionization range and reduced fragmentation relative to conventional APCI and EI sources.
• To showcase routine pesticide screening, nitrosamine quantification, perchlorinated pesticide and PCB analysis, non-polar hydrocarbon profiling, and untargeted component identification in unknown matrices.

Methods and Instrumentation

• SICRIT® soft-plasma ion source mounted directly on the atmospheric inlet of various mass spectrometers (SCIEX QTRAP and TripleToF, Agilent Ultivo QQQ, Orbitrap LTQ, and instruments from Thermo, Bruker, Waters and Shimadzu).
• Three simultaneous ionization mechanisms: ESI-like proton transfer via hydronium clusters, APCI-like gas-phase ion chemistry, and PI-like UV photon-induced ionization.
• Ambient-pressure, flow-through geometry enabling direct analysis of solids, liquids, and gases without additional reagents or consumables.
• Coupling includes a GC-SPME module for solid-phase microextraction and seamless integration with LC or SFC systems when needed.

Main Results and Discussion

• Routine Pesticide Analysis: GC-SICRIT®-MS yielded high signal-to-noise ratios and sharp chromatographic peaks for over 30 regulated pesticides at 1 pg on-column, outperforming GC-APCI by up to two orders of magnitude in sensitivity for many compounds.
• Nitrosamines Quantification: Achieved limits of detection in the femtogram range (69–1395 fg) for nine EPA 521 nitrosamines with a 0.1 μL injection, approximately 30× more sensitive than LC-APCI on the same QQQ system.
• Perchlorinated Pesticides and PCBs: Demonstrated detection of heavily chlorinated molecules in negative and positive ion modes, delivering intact molecular ions ([M–H]–, [M]+) with minimal fragmentation and detection limits below 5 pg on full-scan Orbitrap.
• Non-polar Hydrocarbons: GC-SICRIT®-HRMS generated quasi-molecular adducts ([M–3H+O]+) for n-alkanes C8–C20, enabling unambiguous chain-length assignment and reliable calibration over μg/mL levels with high linearity.
• Untargeted Screening: Integration with an LC-MS non-target database and data-dependent acquisition allowed automated identification of unknown components, combining retention time, accurate mass and MS/MS spectra.

Benefits and Practical Applications

• Single ion source covers ionization ranges previously requiring ESI, APCI and EI, reducing instrument fleet and maintenance.
• Soft ionization simplifies data interpretation by preserving molecular ions and enabling advanced acquisition modes such as SWATH/DIA.
• Ambient sampling eliminates extensive sample preparation, accelerating throughput in QA/QC, environmental testing, food safety and pharmaceutical analysis.
• Vendor-agnostic compatibility allows cost-effective upgrades of existing mass spectrometers without modifying chromatography setups.

Future Trends and Applications

• Expansion of non-targeted workflows combining GC-SICRIT® with high-resolution mass spectrometry for environmental, metabolomics and forensic applications.
• Integration with automated sampling devices and robotics for high-throughput screening in clinical and industrial laboratories.
• Development of tailored soft-ionization protocols for labile biomarkers, polymer degradation products and emerging contaminants.
• Potential extension to imaging applications via laser ablation coupled to SICRIT®-MS for spatially resolved chemical mapping.

Conclusion

SICRIT® presents a versatile, soft ionization interface that unifies GC and LC-MS capabilities, delivering enhanced sensitivity, broad analyte coverage and streamlined workflows. Its unique three-pronged ionization approach and ambient sampling facilitate both targeted and untargeted analyses across diverse compound classes with minimal fragmentation. Widespread adoption promises greater efficiency and deeper insights in routine testing and advanced research.

References

• Manufacturer application notes on SICRIT® ionization technology
• EPA Method 521 for nitrosamines
• NIST Chemistry WebBook spectral data
• SCIEX, Thermo, Agilent product literature