Using Multi-Dimensional GC with a GC-Orbitrap to Separate Isomers for Identification of Unknowns

Importance of the Topic

Multi-dimensional gas chromatography with heart-cutting and high-resolution accurate mass detection addresses the challenge of separating co-eluting isomers in complex matrices such as essential oils, improving identification confidence and analytical accuracy.

Objectives and Study Overview

This work demonstrates the use of a microfluidic Deans’ Switch device coupled to a Q Exactive GC Orbitrap system to separate and identify overlapping monoterpenes in lemon oil. The primary aim was to isolate limonene, ocimene, and linalool fractions and confirm their identities through HRAM library matching.

Methodology

Lemon oil diluted in hexane:acetone (9:1) was analyzed on a TRACE 1310 GC system. Timed heart-cutting transfers targeted chromatographic bands from the non-polar primary column to a polar secondary column. Data acquisition and processing were performed using TraceFinder 4.1 software and an HRAM GC-Orbitrap library.

Used Instrumentation

• Microfluidic Deans’ Switch with five-port plate
• Primary column: TG-5SilMS (30 m × 0.25 mm × 0.25 µm)
• Secondary column: TR-WaxMS (30 m × 0.25 mm × 0.25 µm)
• TRACE 1310 GC system with Instant Connect FID
• Q Exactive GC Orbitrap MS
• TraceFinder 4.1 software and HRAM GC-Orbitrap library

Main Results and Discussion

The primary run detected a prominent limonene peak at 10.99 min. Heart-cutting into the secondary column revealed baseline separation of ocimene (13.23 min), linalool, and an additional interference peak. Mass accuracies below 1 ppm enabled unambiguous identification. Multiple heart-cuts demonstrated highly reproducible retention times without drift.

Benefits and Practical Applications

• Effective resolution of co-eluting isomers in complex samples
• High confidence in compound identification via HRAM mass accuracy
• Reproducible heart-cutting with inert, zero-dead-volume connections
• Applicable to flavor, fragrance, environmental, and QA/QC analyses

Future Trends and Opportunities

Advances in microfluidic flow control and enhanced data processing are expected to broaden the adoption of multi-dimensional GC–HRAM workflows. Increased automation and integration with predictive analytics will further accelerate isomeric profiling in complex matrices.

Conclusion

The combination of Deans’ Switch heart-cutting with Q Exactive GC Orbitrap MS provides a robust platform for isomer separation and identification, delivering high-resolution chromatographic performance, accurate mass determination, and flexible multi-cut capabilities.

References

• Tranchida P.Q.; Sciarrone D.; Dugo P.; Mondello L. Heart-cutting multidimensional gas chromatography: A review of recent evolution, applications, and future prospects. Anal. Chim. Acta. 2012, 716, 66–75.
• Seeley J.V.; Seeley S.K. Multidimensional Gas Chromatography: Fundamental Advances and New Applications. Anal. Chem. 2013, 85, 557–578.