Methods and apparatus for improving electron capture detectors by collection of ions

Method and apparatus are disclosed for the detection of electronegative chemical species in gas flows, such as exist from gas chromatographs, by sampling the detector volume via an aperture connecting to a lower pressure region containing apparatus to collect and measure the negative ion current. Because of the free diffusion of electrons in the region of the aperture, as opposed to ambipolar diffusion in a conventional electron capture detector volume, the electrons are largely removed from the negatively charged components in the gas stream there. Similarly, positive ion current may be measured, thus extending the analytical capability of the invention to classes of chemical species normally not yielding a response in electron capture detectors