Using a Dual LTM Series II System with Flow Modulated Comprehensive GCxGC

Importance of the Topic

Comprehensive two-dimensional gas chromatography (GC×GC) with flow modulation is a powerful technique for analyzing complex mixtures without cryogenic trapping. The use of a dual low thermal mass (LTM) Series II system with independent ovens enhances separation flexibility and sensitivity.

Objectives and Study Overview

This work demonstrates a GC×GC configuration using a flow modulator coupled to two LTM modules for simultaneous second-dimension separations with different column chemistries to maximize analytical information.

Methodology and Instrumentation

A three-oven Agilent 7890A GC equipped with a Capillary Flow Technology (CFT) differential flow modulator splits the effluent into two parallel LTM Series II modules. Each column has its own temperature program, enabling independent optimization. Typical column set:

• 1st dimension: 20 m × 0.18 mm ID × 0.25 µm DB-5ms
• 2nd dimensions: 7 m × 0.25 mm × 0.2 µm HP-INNOWax and 5 m × 0.25 mm × 0.15 µm DB17HT

Main Results and Discussion

The dual LTM system successfully separated jet fuel components, fragrance additives, lime oil constituents and biodiesel methyl esters. Independent temperature control allowed the use of lower phase ratio columns and temperature offsets to avoid wraparound and improve group resolution. Distinct polarity columns provided complementary selectivity in parallel 2D images.

Benefits and Practical Applications

• Enhanced peak capacity and resolution for complex sample analysis
• Flexible column choice and temperature programming to target specific analytes or groups
• Efficient classification and group determination in fuels, fragrances and biofuels
• Reduced reliance on cryogenic cooling and simplified modulation

Future Trends and Potential Applications

Novel column combinations, reversed polarity configurations and integration with chemometric tools will further expand GC×GC capabilities. Advances in LTM technology and multi-modulator designs may lead to higher throughput and deeper chemical profiling.

Conclusion

The Agilent dual LTM Series II flow-modulated GC×GC system offers enhanced analytical flexibility by combining independent oven control with parallel second-dimension separations. This approach extends the power of GC×GC for complex mixtures across industries.

References

• Roger L. Firor. Comprehensive Flow Modulated Two-Dimensional Gas Chromatography. Application Note 5989-6078EN, Agilent Technologies, 2008.
• Roger L. Firor. Comprehensive GC System Based on Flow Modulation for the 7890 GC. Application Note 5989-8060EN, Agilent Technologies, 2009.