Gas-liquid chromatography, usually referred to as gas chromatography (GC), is a type of column chromatography where the absorbing, stationary, medium is a liquid of low-volatility, called the liquid phase, and this is dispersed over the surface of an inert solid support which does not itself adsorb the components but which merely acts to hold the liquid phase in a stable dispersed form so as to present a large contact area.
GC involves the sample being vaporised and injected into the head of the chromatographic column. The sample is introduced to the column via an injection port and the volatile mixture is transported through the column by a chemically inert gas carrier gas. The components of the mixture are distributed between the gaseous and liquid phases and so travel more slowly than the carrier gas stream due to the retarding effect of the liquid phase. These phase differences allow considerably faster separations to be carried out than can be achieved in liquid-chromatography. Given a column of sufficient length the components will become separated as a result of differences in the retarding effect.
In the Celignis laboratory we use an Agilent 680 GC equipped with the ability to operate two detectors simultaneously. One of these is a flame ionisation detector (FID) which is selective for most organic compounds, has a high sensitivity, a large linear response range, and produces little noise. The effluent from the column is mixed with hydrogen and air, and ignited. The organic compounds that burn in the flame produce ions and electrons that conduct electricity through the flame, a large electrical potential is applied at the burner tip and a collector electrode is located above the flame. This allows the current to be measured. Given that FIDs are mass sensitive and not concentration sensitive, changes in the gas flow rate do not affect the response of the detector. However, FIDs are only suitable for compounds containing hydrocarbons due to the ability of the carbons to form cations and electrons upon pyrolysis, so allowing for a current to be generated between the electrodes. Also, as the FID results in the combustion of the effluent, it is not possible to undertake mass spectrometer analysis when this detector is used alone.
The second detector is a Thermal Conductivity Detector (TCD) which functions based on the thermal conductivity of the contents of the passing gas flow. We typically use helium as the carrier gas when using this detector since it has a relatively high thermal conductivity. Hence, when the analytes elute from the column they will result in a decrease in the thermal conductivity and an associated response in the detector. The sensitivity of the detector decreases as gas flow increases. Since TCDs do not change the composition of the passing compounds, the output of the GC can then be fed to the Mass Spectrometer (MS) for further analysis.
If two molecules have the same retention time GC equipment cannot differentiate between these as only a singular peak will be seen. Mass Spectrometry (MS), however, involves the breaking up of these molecules into ionized fragments, with known characteristic fragmentations associated with different molecules. These fragments are distinguished according to their mass to charge ratio, visualised on a mass spectrum, which plots the ion signal as a function of this ratio.
Use of the GC-MS system at Celignis
Currently, we our using our GC-MS for the analysis of bio-oils produced from pyrolysis processes. We are also working on using this device to develop a range of other analytical techniques for various products and analytes of relevance to the biomass and biofuels sector. If you would like us to undertake a custom analysis using this system then please get in touch.
Analysis Packages that Use Our Gas Chromatograph with Mass Spectrometer (GC-MS)
Celignis is a partner in 3 ongoing CBE projects: UNRAVEL
and PERFECOAT are RIA (Research and Innovation Action) projects, whilst VAMOS is an Innovation Action project.
Additionally, Celignis was a partner in the BIOrescue RIA project which was completed in 2019.
Presentation and Exhibition Stand at IBioIC Annual Conference
We will be exhibiting at the event in Glasgow, UK, on June 6-7
The IBioIC Annual Conference makes a welcome return to Glasgow. The title of the event is "The Just Transition of Biotechnology - How sustainable development in industrial biotechnology can secure Scotland's path to Net Zero".
We are pleased to be exhibiting at the event, on June 6-7 at the Technology & Innovation Centre in Glasgow, UK. We look forward to discussing our range of analytical and bioprocess development services for bioeconomy stakeholders.
Our CIO Lalithawill also be giving a presentation at the event about our participation in EnXylaScope a collaborative research project funded by the the Horizon Europe programme.
Here you can download soft copies of the brochure,
It explains the background to the project and its targets for xylan extraction and modification
An introductory video to the EnXylaScope project (funded by Horizon Europe and technically led by Celignis) has been released. It has been prepared by our fellow consortium partner Loba and details the rationale for the project and the technical advances that the project will make, leading to an efficient and commercially-viable process for the extraction of xylan and its modification so that it can be incorporated into a range of consumer products.
Click here to learn more about the project and Celignis's central contributions to it and here to view the video on YouTube.
It details the exciting progress already made in the project
The newsletter covers the project's activities in the search for xylan debranching enzymes (a WP with extensive involvement from Celignis) and on the extraction and modification of xylans for consumer products (a WP led by Celignis). Click here to view the newsletter.
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