PULSED DISCHARGE ELECTRON-CAPTURE DETECTOR OPERATING IN THE CONSTANT-CURRENT MODE BY MEANS OF FEEDBACK DC BIAS VOLTAGE

A feedback de bias voltage has been utilized to established a constant -current operation mode (cc-mode) for the pulsed discharge electron ca pture detector (PDECD). The feedback voltage is directly proportional to the concentration of analyte in the detector cell and can function as output. Working in this mode, the PDECD has a linear dynamic range of 1 x 10(5) for CCl4 and 1 x 10(4) for pesticide-almost 1 order of ma gnitude better than in the previously documented constant-potential mo de (cp-mode). The minimum detectable quantity for CCl4 is 1.5 fg (10(- 15) g) and for lindane, 16 fg, This paper compares the operation of th e PDECD in the cc-mode and in the cp-mode, Our findings indicate that a PDECD operating in the cc-mode has relative response, temperature de pendence, and dopant gas effects similar to a PDECD in the cp-mode und er the same experimental conditions, but has advantages of higher sens itivity, faster response, and simpler operation.