Characterization of the Pulsed Discharge Electron Capture Detector

Abstract

A new version of the pulsed discharge electron capture detector (PDECD) has been developed and characterized. Changes to the old version include a slightly altered detector geometry, replacement of the polymer insulation with sapphire and quartz, and the use of methane dopant gas instead of nitrogen or hydrogen. Various operating parameters have been investigated and optimized, including discharge current, dopant gas, bias voltage, and sample introduction position. The resulting detector is more inert and more sensitive (a limit of 36 fg for lindane) and capable of operation at temperatures as high as 400 °C. By running 23 halocarbon compounds on the improved PDECD and on a (63)Ni-ECD using the same GC system, we find that the PDECD is superior to (63)Ni-ECD in terms of sensitivity, linearity, and response time. We attribute the enhanced sensitivity to a lower positive ion concentration, which in turn lowers the electron-positive ion rate of recombination. Pesticides (including some real-world samples) have also been analyzed on the PDECD. The results demonstrate that the PDECD can replace the radioactive ECD typically used in these analyses.

Detection of organotin, organomercury, and organolead compounds with a pulsed discharge detector (PDD)

“…Response is now selective since only high electron affinity compounds [4] eluting from the column will capture electrons, causing a drop of the standing current. A bias voltage is adjusted to maintain a constant standing current, producing the response signal [4,5].…”

“…Response is now selective since only high electron affinity compounds [4] eluting from the column will capture electrons, causing a drop of the standing current. A bias voltage is adjusted to maintain a constant standing current, producing the response signal [4,5]. Recent applications of the PDD detector include analysis of organochlorine pesticides [6], natural gas [7], atmospheric formaldehyde [8], and dissolved gases [9].…”

Pulsed discharge detector: theory and applications

“…These thermalized electrons can be more readily captured by analytes with high electron capture coefficients [11]. Therefore, the ideal dopant has a low ionization potential and a large cross-sectional area [12]. Hydrogen, carbon dioxide, ammonia, trimethylamine, [6,11] methane, nitrogen [6,11,12] and xenon [12] have been examined as potential dopants.…”

“…Therefore, the ideal dopant has a low ionization potential and a large cross-sectional area [12]. Hydrogen, carbon dioxide, ammonia, trimethylamine, [6,11] methane, nitrogen [6,11,12] and xenon [12] have been examined as potential dopants. Overall, methane and xenon are considered to provide the best results with preference to xenon since it can be purified to levels similar to helium [12].…”

Development of a Mesoscale Pulsed Discharge Helium Ionization Detector for Portable Gas Chromatography

“…10,11 The reasons for selecting the PDHID for miniaturization included the fact that it is both an universal and a selective detector, whilst not requiring radioactive isotopes for effecting the ionization of VOCs prior to detection. 12,13 The PDHID employs photons generated during a helium (He) plasma discharge to photoionize the VOCs emerging from GC columns. The Hopfield emission band of He produces photons with an energy interval of 13.5 to 17.7 eV, which will ionize almost all VOCs with the possible exception of neon (Ne) and He itself.…”