Gas Chromatography Detectors - Ionization Detectors > The Pulsed Discharge Electron Capture Detector > Page 78

 

The electrons driven by appropriate potentials applied to each electrode into the section between the third and forth electrode and finally collected on the forth electrode. The collector electrode potential (the potential between the third and forth electrodes) is pulsed at about 3 kHz with a pulse width of about 23 msec and has a pulse height of about 30 V. The device functions in the same way as the conventional electron capture detector with a radioactive source. The column eluent enters just below the third electrode, any electron capturing substance present removes some of the free electrons and the current collected by the fourth electrode falls. The sensitivity claimed for the detector is 0.2 to 1.0 ng [9] but (as already discussed) this is not very informative as its significance depends on the characteristics of the column used and on the (k') of the solute peak on which the measurements were made.