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| What is ECD? |
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| The development of ECD Since the advent of ECD, people have continuously improved and perfected it to make its structure and performance more ideal.For the past few decades, the most practical two major advances have been to replace the 3H source with a 63Ni source and to replace the other methods with a fixed base current pulse-modulated voltage.Definition of ECD The Electron Capture Detector (ECD) is the most sensitive gas chromatograph detector and the first selective detector.It is only responsive to compounds that trap electrons, such as halogenated hydrocarbons, compounds containing heteroatoms such as N, O, and S.CD is one of the gas phase ionization detectors, but its signal is different from other ionization detectors such as FID. The signal such as FID is the increase of the base stream, and the ECD signal is the decrease of the high background base stream.The downside of ECD is that the linear range is small, usually only 102-104.The ECD system consists of an ECD pool and detection circuitry.ECD principle The carrier gas and the purge gas flowing out of the column enter the ECD pool and are ionized under the bombardment of the β-ray emitted by the source to generate a large amount of electrons.Under the action of the power source, cathode and anode electric field, the electrons flow to the anode to obtain a base flow of 10-9-10-8A.Negative peaks are inconvenient to observe and process. The polarity is converted into a positive peak.
ECD is classified into many methods for ECD classification. Familiar with these classification methods, you can better understand their operational characteristics, so that they can be reasonably selected for different analysis needs.Although non-radioactive ECD has the advantage of being commercially available and has no radioactivity, it uses high-purity He and some rare gases as carrier gas in the operation. The ECD structure and electronic equipment are also complicated, and the operation characteristics are alsoSome shortcomings, so it is currently in the stage of perfect promotion and use.These three kinds of rays have a certain energy, which can ionize the gas and other substances, wherein the α-ray ionization is the strongest, the α-ray can generate 105 ion pairs per centimeter of stroke, and the β-ray can generate 102-103 ion pairs per centimeter.While γ is weak, only one pair of ions is produced per cm.The β source has moderate ionization and penetration strength, so it is most suitable for ionizing radiation source; 2 The source radiant energy should be large enough to provide the necessary ion current; 3 ray’s range should be short enough to facilitate structural design and safety, althoughThis is in contradiction with the requirements for radiant energy. |
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