Flame ionization detector

The flame ionization detector - FID short - is a detector for organic compounds, the (GC) is mainly used in conjunction with a gas chromatograph. Other areas of application of the FID are the wastewater monitoring for volatile hydrocarbon-containing substances ( with vorgelagertem stripping) as well as the indoor and outdoor air monitoring for hydrocarbons.

Principle of operation

Operating principle is to measure the conductivity of a detonating gas flame ( the fuel gas is hydrogen), between two electrodes. Analytes can be transported by a carrier gas stream into the flame, and there ionized thermally. Released during the ionization electrons are collected ( by means of a grid which is mounted to the flame ) and recorded by a connected recorder or data system as a peak.

The FID detector is the most commonly used in gas chromatography since it combines robustness with high sensitivity. An FID is up to 1000 times as sensitive as a thermal conductivity detector. Moreover, the detector signal over a wide concentration range is linearly proportional to (more specifically, for its carbon content ) the amount of analyte. Therefore, the concentration of a hydrocarbon of the signal without any calibration can be estimated so that the detector can easily be used for quantification.

Some organic substances (for example, formic acid, acetaldehyde ), however, have a lower detectability, as they are previously thermally decomposed in the column (e.g., formic acid decomposes to carbon monoxide and water). Substances that have little or no appeal are:

The limit of detection is in addition to the dosing amount dependent on the substance to be analyzed.

In contrast to the ECD or TCD FID has a destructive effect. This means that the sample to be analyzed is destroyed (in this case by combustion).

Related devices

  • Detector (chromatography )
Indoor air quality Oxyhydrogen Analysis Ammonia Electron capture detector Nitrogen–phosphorus detector
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