GC coupling to LC MS instruments

Importance of the topic

Gas chromatography–mass spectrometry (GC-MS) and liquid chromatography–mass spectrometry (LC-MS) are cornerstone techniques in analytical chemistry, yet each has its limitations. The development of a universal, soft ionization interface that seamlessly links GC separation with LC-MS instrumentation can significantly expand analyte coverage—from nonpolar to polar molecules—while improving sensitivity, reducing fragmentation and simplifying workflows. The SICRIT® source addresses these needs by offering a vendor-independent, ambient-pressure, dielectric barrier discharge interface that ionizes analytes gently during transfer into the MS.

Objectives and overview

The study introduced and evaluated the patented SICRIT® ionization technology for coupling GC to LC-MS systems, aiming to:

• Enable direct, soft ionization of a broad range of compounds without extensive sample preparation
• Combine the high separation power of GC with the versatile detection capabilities of various MS platforms
• Demonstrate improved sensitivity and reduced fragmentation for routine and advanced analyses

The manuscript covered the SICRIT® geometry, ionization mechanisms, coupling configurations, and performance data across multiple applications.

Methodology and instrumentation

The SICRIT® interface consists of a concentric dielectric barrier discharge chamber mounted at the MS atmospheric-pressure inlet. It generates a cold plasma that produces three simultaneous ionization pathways—proton transfer (ESI-like), chemical ionization (APCI-like) and photoionization (PI-like)—using ambient gases.
The source was coupled to GC systems equipped with DB-5 columns and various autosamplers, using helium as carrier gas and splitless injection. Detection was performed on vendor-independent triple quadrupole (e.g., SCIEX 6500 QTRAP, Agilent Ultivo) and high-resolution instruments (Orbitrap, TripleTOF).

Main results and discussion

• In pesticide screening, GC-SICRIT®-MS achieved signal-to-noise ratios 2–30 times higher than GC-APCI, with low-pg on-column sensitivity and excellent peak shapes.
• Nitrosamines, undetectable by LC-ESI or APCI, were measured down to femtogram levels via GC-SICRIT®-MS, revealing ~30× greater sensitivity than LC-APCI.
• Perchlorinated pesticides and PCBs were efficiently ionized in negative and positive modes, respectively, yielding intact molecular ion or adduct peaks with minimal fragmentation and LODs below 5 pg on column in full-scan Orbitrap mode.
• GC-SICRIT®-HRMS delivered quasi-molecular ions for n-alkanes, enabling unambiguous chain-length identification and accurate quantification over a µg/mL range, which is challenging for EI or LC-MS due to fragmentation or lack of ionization.
• In non-target screening of unknown mixtures, the soft ionization allowed automated identification by retention time, accurate mass and MS/MS patterns using existing LC-MS databases, demonstrating the interface’s utility for comprehensive analyte profiling.

Benefits and practical applications

The SICRIT® interface:

• Reduces or eliminates sample preparation for solids, liquids and gases under ambient conditions
• Unifies the detection of polar and non-polar analytes in a single run, bridging GC and LC worlds
• Provides vendor-agnostic coupling to all major MS platforms, saving laboratory space and investment
• Delivers soft ionization that preserves molecular ions, simplifying data interpretation and enabling advanced acquisition strategies (e.g., SWATH, DDA)
• Combines the high chromatographic resolution of GC with high-resolution MS performance for rigorous analyte confirmation

Future trends and applications

Potential developments include:

• Integration with supercritical fluid chromatography (SFC) to further widen analyte coverage
• Miniaturized and field-deployable GC-SICRIT®-MS systems for on-site environmental, food safety or forensic screening
• Expanded non-targeted workflows leveraging machine learning and large spectral libraries to accelerate unknown identification
• Coupling with ion mobility and tandem high-resolution MS to resolve isomers and complex mixtures

Conclusion

The SICRIT® ionization source represents a versatile, soft and sensitive interface for GC-MS and LC-MS coupling. By enabling simultaneous ESI-like, APCI-like and PI-like mechanisms within a compact, consumable-free chamber, it bridges the gap between separation techniques, enhances analyte range, and streamlines both routine and advanced analytical workflows.

Reference

No formal references were provided in the original text.