Please note: the articles have been translated automatically.
Flame ionization detectors (FID) are commonly used to detect small molecular weight compounds. The FID is often used for detection after the sample has been separated in a gas chromatography. Samples can be gaseous or liquid (is vaporized during injection) or even solid (outgassing of solid samples – extraction in a headspace).
Schematic representation of an FID. H2 is burned. The voltage is measured between the combustion tube, to which current is applied, and a collecting electrode above the flame. The more ions there are, the more current flows and the voltage (and thus the measurement signal) increases. The combustion of hydrogen forms almost no ions. These are introduced almost exclusively through the rehearsal.
Amium’s FID is an online detector for the direct determination of pollutant concentrations in air. This means that the sample is not separated.
Since a flame has to be generated with the FID, a fuel gas is required. As a rule, this is hydrogen, since clean combustion to H2O and O2 takes place here. A carrier gas containing the sample is also required. For the direct measurement of air, the air itself serves as the carrier gas.
All molecules that lead to the ionization of the burner flame are detected. It is therefore not possible to distinguish between the individual molecules without first separating them. As a rule, hydrocarbon-containing molecules are recorded here (CH4 – methane, C2H6 – ethane, C3H8 – propane, etc.). We are talking here about the total hydrocarbon concentration (or THC for Total Hydrogen Carbon). Theoretically, other ionizable compounds also lead to a measurement signal, but the hydrocarbons usually make up the majority.
Special features of Amium FIDs
The Amium FID is primarily intended for THC measurement for gaseous samples. It has a self-priming diaphragm pump, including an input filter, and can be calibrated by the user himself with reference gases via a separate sample input.
The interior of the FID is heated to 191 °C to prevent condensation and hydrocarbon deposits. Otherwise, these would be missing in the measurement and a lower concentration could be simulated.
The FID can be embedded in a higher-level monitoring system via various interfaces. It is thus possible to automatically and continuously monitor hydrocarbon-containing pollutants at workplaces. Air can be sucked in at various points in the room via another sampling system and evaluated with a measuring device.
Structure of the stationary FID from Amrum 5601-00170. The device is also designed for installation in a 19 inch rack.
Below is a listing of available concentration ranges, based on methane. The smaller the measuring range, the lower the detectable concentrations and changes in concentration.
- 0-10.000 ppm (default)
- 0-1000 ppm
- 0-100 ppm
- 0-10 ppm (on request)
Portable FID
As a further highlight, the company Amium also offers a portable FID with integrated battery and 2l 200 bar hydrogen bottle. This device can also be used to measure the concentration of hydrocarbons on the move. The specifications of the portable FID are largely comparable to the stationary FID.
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