Development and Application of a Consumable-Free Modulator for Comprehensive Two-Dimensional Gas Chromatography

Abstract

Comprehensive two-dimensional gas chromatography (GC×GC), is a separation method recognized as offering far greater peak capacity than conventional one-dimensional separations. Today, the most frequently used GC×GC systems require consumables such as liquid N2 for the trapping function of the modulator. Although these systems are recognized as being very effective, their initial and running costs are a hindrance to more widespread use. A consumable-free, single-stage thermal modulator for GC×GC has been developed to overcome these problems. The device traps analytes through the use of a specially prepared coated stainless steel capillary compressed between two ceramic cooling pads. Analytes are thermally released from the trap into the secondary column via resistive heating. Thermal treatment of the trapping capillary plays an important role in the function of the device and advanced imaging and material characterization techniques were used to reveal changes in the stationary phase coating of the trap. These experiments revealed the polydimethylsiloxane stationary phase coating was being converted to carbon doped, oxygen rich silica nanoparticles. These spherical particles coated the internal surface of the capillary evenly and provided an effective and highly sorptive phase for use in GC×GC modulation. This modulator’s performance was evaluated by applying it to real world analytical challenges. Samples such as honeybush tea volatiles, polychlorinated biphenyls, perfumes and petroleum products were successfully analyzed with performance comparable to commercially available instruments. This work demonstrates the single-stage, consumable-free GC×GC modulation system described herein is an excellent instrumental option for analysts across a wide breadth of application areas in the world of complex volatile and semi-volatile analysis.