Development of a new consumable-free thermal modulator for comprehensive two-dimensional gas chromatography.

A simple and cost-effective GC×GC modulator requiring no moving parts or consumables, hence suitable for field analysis and monitoring, was developed. The modulator was constructed from a specially designed Silcosteel® trapping capillary, installed outside the GC oven, and coated inside with polydimethylsiloxane (PDMS) stationary phase. Dual-stage modulation was accomplished by resistively heating alternate segments of the trap with a custom-designed capacitive discharge power supply. The performance of the proposed modulator was comparable to many GC×GC systems currently in use, with the injection band widths as low as 60 ms at half height. With proper selection of the stationary phase in the trap, the modulator can be used for the analysis of complex mixtures with volatility range spanning from n-C5 to n-C40.

Stop-flow comprehensive two-dimensional gas chromatography with pneumatic switching.

A new method for performing comprehensive GC x GC in the stop-flow mode is presented. A device was used to pneumatically stop the flow in the first dimension ((1)D) (by applying pressure pulses at the junction between the two columns), while flow was maintained in the second dimension ((2)D). This allowed for better preservation of resolution in the (1)D of the GC x GC chromatograms, and the extension of the (2)D's separation space, reducing or eliminating the extent of wraparound. When increased flow rates in the (2)D were used, sensitivity enhancements were also observed.

Thermal desorption comprehensive two-dimensional gas chromatography for in-situ measurements of organic aerosols.

The complexity of organic composition and temporal variability of atmospheric aerosols presents an extreme analytical challenge. Comprehensive two-dimensional gas chromatography (GC x GC) has been used on time integrated filter samples to reveal the presence of thousands of individual organic compounds in aerosols, but without defining the temporal variability in composition ideal for providing information on source resolution and human exposure to specific pollutants. We hereby introduce a new instrument, 2D-TAG, which combines our in-situ thermal desorption aerosol GC (TAG) instrument with GC x GC allowing for dramatically improved separation of organics with automated measurements at hourly timescales.

Comprehensive two-dimensional gas chromatography (GC x GC) in environmental analysis and monitoring.

Compared to conventional one-dimensional gas chromatography (1D-GC), comprehensive two-dimensional gas chromatography (GC x GC) offers increased peak capacity, improved resolution and enhanced mass sensitivity. In addition, it generates structured two-dimensional (2-D) chromatograms, which aids in the identification of compound classes. Sample preparation procedures can often be minimized, or even eliminated in some cases, due to the superior separating power offered by the technique. All of these advantages make GC x GC a very powerful tool in environmental analysis involving the determination of trace levels of toxic compounds in complex matrices. This review paper summarizes and examines the historical and recent GC x GC applications in environmental analysis and monitoring.

The evolution of comprehensive two-dimensional gas chromatography (GC x GC).

For a technology little over a decade old, comprehensive two-dimensional gas chromatography (GC x GC) has quickly reached the status of one of the most powerful analytical tools for volatile organic compounds. At the heart of any GC x GC system is an interface, which physically connects the primary and the secondary columns and acts to preserve the separation obtained in the first dimension (first column) while allowing additional separation in the second dimension. The paper presents a review of the technology, including fundamental principles of the technique, data processing and interpretation and a timeline of inventive contributions to interface design. In addition, applications of the technique are presented, with a more detailed discussion of selected examples.