GC soft ionization coupling to LC-MS with SICRIT® (Thermo LTQ Orbitrap XL)

Significance of the Topic

Gas chromatography–mass spectrometry (GC-MS) and liquid chromatography–mass spectrometry (LC-MS) have traditionally occupied separate niches. GC-MS excels in resolving volatile compounds and broad electron ionization, while LC-MS offers soft ionization, high sensitivity and accurate mass detection. Bridging these worlds enables analysts to exploit high chromatographic resolution alongside soft, high-resolution MS data in a single workflow.

Objectives and Study Overview

This application note demonstrates a plug-and-play interface of any conventional GC to a high-resolution LC-MS system using the SICRIT® GC-SPME module. A Thermo Trace GC Ultra was coupled to a Thermo LTQ Orbitrap XL to analyze a series of trialkylamines. The goals were to assess soft ionization performance, sensitivity, repeatability, dynamic range and non-target screening capability.

Methods and Instrumentation

Sample introduction was performed by GC splitless injection of 1 µL of calibration standards in n-hexane. A Restek RXI-5 ms capillary column (30 m × 0.25 mm ID, 0.25 µm) operated at constant He flow (2 mL/min) with a temperature program (40 °C hold 0.5 min, ramp 40 °C/min to 280 °C, hold 3 min). The SICRIT® soft ionization source ran at 1.5 kV, 15 kHz. Full-scan MS data (m/z 143–269) were acquired on the Orbitrap with 5 ppm mass tolerance. Peak picking and quantitation used Thermo Xcalibur software.

Used Instrumentation

• Thermo Trace GC Ultra
• Thermo LTQ Orbitrap XL
• SICRIT® GC-SPME soft ionization source
• Restek RXI-5 ms column (30 m × 0.25 mm, 0.25 µm)
• MS-grade n-Hexane (Sigma Aldrich)

Main Results and Discussion

• Extracted ion chromatograms of methyl, tri- and trialkylamines at 100 pg on-column showed clear, well‐resolved peaks, including separation of tripentylamine isomers.
• Full-scan mass spectra were dominated by [M+H]+ with minimal fragmentation, confirming soft ionization.
• Repeatability for seven injections of 1 ppm standards yielded RSD values below 5 %, demonstrating stable ionization.
• Calibration curves over 1–1000 ppb exhibited excellent linearity (R2>0.999).
• The method achieved a dynamic range exceeding three orders of magnitude and sensitivity down to 1 pg on-column.

Benefits and Practical Applications

• Plug-and-play compatibility allows any GC to interface with high-resolution LC-MS platforms.
• Soft ionization expands compound coverage and reduces fragmentation, aiding non-target screening.
• High mass accuracy (<1 ppm) supports unambiguous identification of unknowns.
• Existing LC-MS software workflows can be repurposed for GC quantitation.

Future Trends and Opportunities

The SICRIT® coupling concept may be extended to diverse GC sampling techniques (SPME, thermal desorption), and to other high-resolution MS instruments. Advances could include automated method translation, integration with data-independent acquisition for complex matrices, and expanded use in environmental monitoring, metabolomics and industrial QA/QC.

Conclusion

The SICRIT® GC-MS interface offers a straightforward, robust method to combine GC separation with soft, high-resolution MS detection. It delivers sub-picogram sensitivity, broad dynamic range and excellent repeatability, unlocking new capabilities for both targeted and non-targeted analyses without major hardware or software changes.