Recent Developments in Analytical Science - Gas Chromatography

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  • Published: Jul 18, 2016
  • Channels: Ion Chromatography / Electrophoresis / Proteomics & Genomics / HPLC / Gas Chromatography / Proteomics / Infrared Spectroscopy / MRI Spectroscopy / NMR Knowledge Base / X-ray Spectrometry / Base Peak / Atomic / Raman

Gas Chromatography

The chromatography market is another analytical chemistry sector that is thriving, due in major part to food safety and pharmaceutical testing. The instrument market is expected to rise more than USD 2,121 million between 2015 and 2020, with corresponding increases in sales of chromatography reagents, resins, columns and consumables. [ref] [].

One of the two main types of chromatography is GC, a technique that originated about 60 years ago but is still being developed and improved. For instance, there are several popular and longstanding types of detector such as the mass spectrometer, field ionisation detector, thermal conductivity detector, electron capture detector, flame photometric detector and atomic emission detector. But new detectors continue to be developed, albeit sporadically.

In 2014, the vacuum ultraviolet absorption array spectrometer was announced. It measures broadband absorption at 115-240 nm and can detect any compound eluting from the GC because all chemical species have unique gas-phase spectra at these wavelengths. So, compounds that are difficult to detect by FID or MS, like fatty acids, hydrocarbons, PAHs, water and carbon dioxide, are successfully monitored. It can also distinguish between isomeric and isobaric compounds, giving additional selectivity.

GC phases are also targets for improvement. Over the years, many modifications have tweaked the selectivity, thermal stability and inertness of the phases but, occasionally, new materials are adapted. This is the case for ionic liquids, which offer improved polarity and low vapour pressure. However, one of the key attractions is the vast array of anionic and cationic components that can be combined, offering unprecedented opportunities to tune a phase for a particular application. They have been used in the GC separation of many different classes of compounds to date, including pollutants in wastewater, petroleum hydrocarbons and plasticisers and will surely be extended to more applications in the near future.42

In cases where one type of column fails to provide adequate resolution, two columns with different separation chemistries can be joined in tandem. All of the eluate leaving the first column can be passed to the second column, generally via a thermal modulator. Alternatively, only selected fractions from the first column are transferred in a heartcutting technique. These 2D processes are more complex to operate but they provide better resolution and more compound identifications for complex mixtures such as environmental and food science studies.

In common with other analytical techniques, miniaturisation is one of the ongoing trends in GC. Recent novel systems include a GC-on-a chip which has a monolithic column and a micro helium discharge detector, allowing separation of mixtures within one minute at a sensitivity that matches that of FID.43 A second chip-based system uses planar columns or microchannels, selecting coatings that permitted conventional and chiral separation of plant volatiles.44

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