CHARACTERIZATION OF THE FUSSED DISCHARGE ELECTRON-CAPTURE DETECTOR

A new version of the pulsed discharge electron capture detector (PDECD ) has been developed and characterized. Changes to the old version inc lude 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 be en investigated and optimized, including discharge current, dopant gas , bias voltage, and sample introduction position. The resulting detect or is more inert and more sensitive (a limit of 36 fg for lindane) and capable of operation at temperatures as high as 400 degrees C. By run ning 23 halocarbon compounds on the improved PDECD and on a Ni-63-ECD using the same GC system, we find that the PDECD is superior to Ni-63- ECD in terms of sensitivity, linearity, and response time. We attribut e the enhanced sensitivity to a lower positive ion concentration, whic h its turn lowers the electron-positive ion rate of recombination. Pes ticides (including some real-world samples) have also been analyzed on the PDECD. The results demonstrate that the PDECD can replace the rad ioactive ECD typically used in these analyses.