GCxGC, which is also referred to as comprehensive GC, is an advanced type of multidimensional GC. GCxGC technology is a relatively recent development, and provides major advantages over conventional MDGC techniques. The industries in which GCxGC is most popular are much the same as the wider GC market. The market demand for GCxGC consists primarily of aftermarket add-ons to existing GC systems, although demand for preconfigured GC instruments is also significant.
Conventional MDGC, which is almost as old as GC itself, makes use of two columns of differing chemical properties connected in series. However, these columns generally have similar separation speeds and, without the ability to trap segments of the primary column separation, this configuration is only able to perform a secondary separation on a selected portion of the primary separation, which is referred to as a “heart cut.”
In order to perform a secondary separation on all of the primary separation, the secondary column has to be much faster than the first: this is where GCxGC comes in. First commercialized in the early 1990s, GCxGC utilizes a much shorter, and therefore faster, secondary column, combined with a thermal modulation device to control the flow between the two columns. Continued improvement in both the cryogenic trapping hardware and software have been the major GCxGC improvements in recent years.
Flame ionization detectors (FID) have traditionally been the most commonly used detector with GCxGC, but time-of-flight (TOF) MS has been increasingly combined with the technique. MS effectively adds a third dimension of separation, which makes GCxGC-TOF MS an extremely high-resolution gas analysis technique. TOF MS is the only MS method fast enough to effectively analyze all of the peaks coming out of the GC, although there is significant developmental work in progress to develop trapping methods that would allow other mass analyzers to be used, such as quadrupoles.
GCxGC is most useful in moderate to complex samples, which are common in most of the industries in which conventional GC is used. The oil and gas, flavor and fragrance, and environmental industries are the three largest markets for GCxGC. A smaller, but fast-growing application is metabolomics. The extremely high resolution that GCxGC, and especially GCxGC-TOF MS, can provide is potentially useful in the development of personalized medicine due to the complexity of the samples. However, it is not clear yet just how big demand from this application will become.
Although GC systems are sometimes preconfigured for GCxGC by vendors such as LECO, most of the demand for GCxGC is in the aftermarket, as end-users can generally modify their existing GC systems with products from vendors like Zoex. Worldwide demand for GCxGC is estimated to be around $15 million, and should continue to show double-digit growth.
GCxGC at a Glance:
• Thermo Fisher Scientific
• Oil and Gas
• Flavors and Fragrances
• GC: $20,000–$80,000
• TOF MS: $75,000–$300,000