ELECTRON CAPTURE DETECTOR (ECD) 



Gas Chromatography – Electron Capture Detector or GC-ECD is a technique used to analyse halogenated compounds and is primarily used in the environmental, forensic and pharmaceutical markets. In the electron capture detector a beta emitter such as radioactive tritium or 63Ni is used to ionize the carrier gas. Fast beta particles generated by the radioactive source collide with the molecules of the carrier or make-up gas. By impact ionization,, free slow-moving electrons are produced which generate a measurable and steady current. If the GC effluent contains organic molecules with electronegative functional groups, such as halogens, phosphorous and nitro groups, electrons will be captured and the current will be reduced. In comparison to a signal without sample compounds, the reduction in electron fl ow is proportional to the quantity of electrophile sample components. Electron Capture Detectors are up to 1000 times more sensitive than Flame Ionization Detectors and were the first detectors able to measure components at parts-per-billion (ppb) and parts-per-trillion (ppt) levels.