For this reason some percentage of methane (5%) is added to the make-up gas argon (the most sensitive gas for an ECD regarding its ionizing capability). This can be achieved by introducing an inert gas into the ECD cell that collides with the rapid electrons and in that way slowing them down. The electrons emitted by the radioactive foil move too fast to be captured by the analyte molecules. This explains why the (linear) dynamic range of the ECD is often limited.Īctually, the mechanism of operation of the ECD is slightly more complex. Since it concerns very small holes, the background current should not be too high. This change in the background current is registered as 'holes' in the background. ![]() When there are electro-negative components present in the carrier gas, the background current is reduced because these components capture electrons. ![]() A current is produced between two electrodes in the detector supplied with a potential difference and this is monitored as a continuous background current. The electron capture detector (ECD) is a selective detector for electro-negative compounds, especially halogens.Ī (beta-ray) radio active source which can ionize the carrier gas is located in the detector.
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