Electron capture detector

An ECD has a non-radioactive electron source 6 for generation of ions in a reaction chamber. The reaction chamber consists of two partial chamber, 2,3 of which one 2 is evacuated and contains the electron source 6, and the other 3 contains connections 12,13 for the feeding in of analysis gas as well as a collector electrode, 9 for detecting ions. The partition 4 between the two partial chambers is permeable for electrons from the source but impermeable for gas molecules. It may be made of a polymer or mica. The electron source 6 may be a thermoemitter or a photocathode as shown, which is irradiated from the outside through a window 15. In this Way, contact between the analysis substance and the electron source is prevented, which increases measurement stability.