GC-FID is the term used for gas chromatograph connected to a flame ionisation detector, which is used for the quantification of organic substances.
Table of contents
- Flame ionisation detector
- Design of a flame ionisation detector
- Applications for gas chromatography
- Summary: GC-FID
Flame ionisation detector
A flame ionisation detector (FID) is a sensor that is used to detect organic compounds, specifically hydrocarbons that have first been separated in a gas chromatograph (GC). Although the GC can also be connected to numerous other detectors or a mass spectrometer (GC-MS), the flame ionisation detector is particularly suitable due to its combination of very high sensitivity and good robustness. The FID can also be used without a gas chromatograph, for instance for monitoring room air as well industrial waste gases and automotive exhaust gases for the concentration of hydrocarbons, or for monitoring the emissions of methane gas, for instance from waste dumps.
GC-FID at Quality Analysis
At Quality Analysis we analyse your plastics for volatile organic compounds and quantify them quickly and reliably. Our experts are also available to assist you at short notice. We take the time to advise you comprehensively so that we can find the most effective and economical analytical method for your task. Irrespective of whether GC-FID or any other method: in the end you receive from us a test report that answers your questions and provides you with practical information for your work.
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Design of a flame ionisation detector
The substances separated in gas chromatography are transported by the carrier gas (mostly helium) to an oxyhydrogen gas flame and ionised there. During ionisation, electrons are detached using two electrodes at which there is a DC voltage. For this purpose, two capacitor plates are typically used, or a metal mesh or ring is placed around the flame. With the latter configuration, the burner nozzle has a double function as it also acts as a return electrode.
Documentation of the results of GC-FID
In all electrode arrangements used, the electrons captured produce a small electrical current. However, because the magnitude of the current is only in the range of a few picoamperes, it must first be amplified before it is recorded in the chromatograph as a peak. This method functions for all organic (= carbon-based) substances, however only to a limited extent for those substances that are already thermally decomposed in the separation column. Halogenated compounds, nitric oxide (NOX) and also carbon monoxide (CO) as well as carbon dioxide (CO2) cannot be verified at all.
Applications for gas chromatography with downstream flame ionisation detector (GC-FID)
GC-FID is an established method in chemical analytics and plays a role in practically all areas in which the quantitative assessment of organic substances is of importance, for instance in pharmaceutics or plastics analytics. The precise, reliable measurements permit the identification of most organic substances, even if these are only present in a very low concentration.
GC-FID in pharmaceutics
In pharmaceutics GC-FID is used in a very wide range of areas. One of its core tasks, however, is the analysis of medicines for any contamination. The medicine-related metabolites contained in samples from patients or test subjects for pharmaceutical research can also be verified. A further application is the determination of the concentration of alcohol in the blood.
In the chemical industry GC-FID is an important method for quality control. This is particularly the case in petrochemicals. For instance, fuels are regularly analysed for their exact composition with the aid of flame ionisation detectors. The composition of kerosene is particularly important for its conversion into energy.
In the area of food safety, GC-FID is used to analyse the food itself (e.g. the verification of pesticides in agricultural products or hormones in meat), on the other hand, it is used to check plastic packaging to ensure the hydrocarbons contained in the packaging do not impair the taste or quality of the foodstuff.
In summary: GC-FID
GC-FID stands for gas chromatography with downstream flame ionisation detector. In this widely used method, the organic substances separated in the gas chromatograph are ionised and the electrons released are then quantified by means of the peaks.