What is GC x GC?

Traditional one dimensional gas chromatography (or 1D GC), the method of separating out the various components of a compound, has been limited in its ability to separate compounds that have a makeup more complex than 50 differing components. As such, chromatographers have sought innovative ways to overcome this problem, by introducing a second or even third dimension to the chromatography process. One such technique is comprehensive gas chromatography, which is better known as GC x GC.

Traditional multidimensional gas chromatography (MDGC) is not comprehensive in its repeat separation methods, with the “heart-cutting” technique only transferring certain parts of the eluate from the first to the second dimension.
 
However, GC x GC eliminates this problem entirely. It does so by introducing a modulator in between the dimension stages. This modulator works to isolate, identify and group together the various components of the eluate, before sending them on to the second dimension. The fact that the entire sample is able to be resubmitted to the second column, as well as being separated out into their differing components, yields several benefits.

The Advantages of GC x GC

Because the entire sample is submitted to column separation twice, the separation capabilities are significantly improved than with traditional 1D GC or MDGC.

The peak compression that is achieved during the modulation part of the process also allows for better sensitivity in the end results. This in turn produces far more detailed data about the sample, partly due to the fact that GC x GC allows for the generation of structured chromatograms, giving more information in sample analysis time comparisons and making it more suitable for sample screening.

The ability to produce two retention times gives a more reliable identification of the peak elution of the sample as well. Furthermore, such a technique is appropriate for all types of injection systems and sample handling methods, and is effective in reducing sample clean-up time and effort.

As such, GC x GC represents an important breakthrough in gas chromatography techniques.

The Applications of GC x GC

Due to its ability to produce more dependable and specific data about the samples, GC x GC can now provide data on other aspects of a compound, such as smell and  flavour, key in the food and fragrance industries. Furthermore, its ability to dampen co-elution and to give more information about signal-to-noise ratios makes it a very useful tool in analysing oil and petroleum samples. This article, Determination of 
Biomarkers in Petroleum by Multidimensional Gas Chromatography: Fundamentals, Applications and Future Perspectives, discusses in more detail the various methods of analysing biomarkers in petroleum and their accompanying merits.