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How does electron Capture (ECD) detection work?
发布时间：2021-05-11
来源：ydlcb 浏览次数：24次
How does electron Capture (ECD) detection work?
A: Electron Capture Device (ECD) uses the radioactive isotope Ni63 (nickel 63) as the ion reflector of the detector. When the carrier gas (usually argon or nitrogen) passes through the radioactive source, the high-energy electrons of the beta ray ionize the carrier gas to form positive ions and slow electrons, and migrate to the positive electrode to form a base flow. When the electronegative SF6 gas probe enters the detector, it traps the slow electrons in the detector to generate negative ions, which travel at a lower speed in the electric field than the free electrons. The negative ions of the gas to be measured are combined with the positive ions of the carrier gas to form neutral chemicals, which are carried out of the detection room by the carrier gas, thus reducing the original base flow. The reduction of the base flow is proportional to the concentration of the measured gas. Through the signal amplifier, the changed basic flow is converted into the output of the concentration indication signal, so as to meet the requirement of detecting the gas concentration. The electronic capture detection instrument consists of a probe and a controller. The probe includes an electron capture detector, a detection tube, a signal amplifier, an indicator light, and a concentration alarm. The controller includes a carrier gas cylinder, a gas control component, a signal control system and a power supply.