3.4 - Non-radioactive electron capture detector based on X-ray ionization for the detection of pollutants
- Event
- 16. Dresdner Sensor-Symposium 2022
2022-12-05 - 2022-12-07
Dresden - Band
- Vorträge
- Chapter
- 3. Umweltsensorik
- Author(s)
- M. Kueddelsmann, E. Buntert, S. Zimmermann - Leibniz University Hannover, Hannover/D
- Pages
- 29 - 34
- DOI
- 10.5162/16dss2022/3.4
- ISBN
- 978-3-9819376-7-1
- Price
- free
Abstract
For analyzing complex mixtures of electron-affine substances by gas chromatography (GC), electron capture detectors (ECD) are preferably used as highly sensitive GC-detectors. ECDs are characterized by their fast response, high linearity of up to four orders of magnitude and detection limits in the pptvrange. GC-ECDs are consequently highly suitable for the analysis of pesticides or other environmental toxins, making GC-ECDs standard instruments in many analytical laboratories [1–3]. In general, high energetic electrons from a radioactive 63Ni source ionize nitrogen in the ECD reaction region to generate a large number of free (secondary) electrons. In the presence of electron-affine substances, the electrons can be captured and the number of free electrons reduces. Thus, the number of free electrons is a measure for the concentration of electron-affine substances. The number of free electrons is measured by applying an electric field guiding the free electrons to a Faraday detector, which is connected to a current amplifier. The high difference in mobility between the free electrons and the ionized electron-affine substances ensures that only the electrons reach the detector if the reaction region geometry and operating parameters are selected appropriately. The negative ions, instead, substantially recombine with the positive ions or leave the reaction region in the gas stream before reaching the detector electrode [4].