Soft Ionization GC Coupling to LC-MS Systems

Significance of the Topic

Gas chromatography–mass spectrometry (GC-MS) and liquid chromatography–mass spectrometry (LC-MS) are complementary techniques widely used in routine analysis. Traditionally, laboratories require separate instrumentation for each technique, increasing capital expenditure, maintenance efforts, and consumable costs. The integration of GC with LC-MS through soft ionization provides a unified platform to extend analyte coverage, enhance sensitivity, and streamline workflows.

Objectives and Overview

The primary goal of the study is to present the SICRIT® solution for seamless coupling of any GC system to existing LC-MS instruments. Key objectives include:

• Demonstrating soft ionization via cold plasma to minimize fragmentation.
• Expanding detectable analyte range from non-polar hydrocarbons to polar small molecules.
• Evaluating performance for both high-resolution non-target screening and triple-quad quantification.

Methodology

The SICRIT® setup employs a gas-tight flow-through design connecting the GC outlet to the LC-MS inlet. A dielectric barrier discharge generates a cold plasma at atmospheric pressure, providing three distinct ionization mechanisms that cover the polarity and mass range of APCI, EI, and partial ESI. This soft ionization reduces in-source fragmentation and preserves molecular ions for accurate mass determination.

Used Instrumentation

• Gas Chromatograph (e.g. Agilent 8860) with touchscreen control and microchannel EPC.
• CTC PAL Autosampler for automated sample introduction and SPME integration.
• SICRIT® Ion Source for cold plasma–based soft ionization.
• SICRIT® SC-30 Control Unit managing plasma parameters and module controls.
• Heated Transfer Line for loss-free, high-temperature sample delivery.
• GC/SPME Module enabling direct coupling of GC or solid-phase microextraction to MS.
• SICRIT® MS Interfaces tailored for major MS platforms (Thermo Fisher, Agilent, SCIEX, Bruker, Waters, Shimadzu, Jeol).

Main Results and Discussion

• Sensitivity Improvement: Locally confined ionization minimizes ion losses, enhancing detection limits for trace analytes such as nitrosamines (LOD down to 0.1 ng/mL).
• Minimal Fragmentation: Comparison with EI spectra of diazinone shows almost no fragmentation under SICRIT®, preserving [M]+ ions for structural confirmation.
• Expanded Analyte Range: Successful detection of n-alkanes for molecular weight determination, PCB congeners via isotopic pattern recognition, and nitrosamines in MRM mode demonstrates broad applicability.
• Flexible Workflow: The solution supports both high-resolution non-target screening (TOF, Orbitrap) and routine triple-quad quantitative analyses without instrument changes.

Benefits and Practical Applications

• Cost Efficiency: One MS platform replaces separate GC-MS and LC-MS systems, reducing capital and operational expenses.
• Laboratory Space Savings: Eliminates need for multiple mass spectrometers and associated infrastructure.
• Streamlined Data Management: Unified software environment avoids data integration from different platforms.
• Versatility: Applicable in environmental monitoring, pesticide residue analysis, food safety, pharmaceutical quality control, and non-target screening in complex matrices.

Future Trends and Applications

Anticipated developments include:

• Integration with advanced data processing and machine learning for comprehensive non-target screening.
• Expansion to real-time and field-deployable systems using ambient air as carrier gas.
• Adaptation for large biomolecules and metabolomic profiling through optimized plasma parameters.
• Combination with multidimensional GC×GC to further enhance separation capacity.

Conclusion

The SICRIT® GC-MS/LC-MS coupling presents a powerful, cost-effective alternative to conventional dual-instrument setups. By combining soft plasma ionization with universal interfacing modules, the technology delivers high sensitivity, reduced fragmentation, and broad analyte coverage, while simplifying laboratory workflows and reducing expenses.

References

• NIST Chemistry Webbook, dielectric barrier discharge data for diazinone fragmentation comparison.