CONSTANT-CURRENT AC ELECTRON-CAPTURE DETECTOR

The constant-current drive is the most popular mode of polarization fo r the conventional (unipolar) electron-capture detector: in this mode, an increase in analyte produces an increase in frequency. In contrast , when the electron-capture detector is operated under a constant-curr ent constraint in the bipolar a.c. mode, an increase in analyte produc es a decrease in frequency in the, roughly, 10(4) to 10(5) Hz region ( as well as an increase in frequency in the, roughly, 10(2) to 10(3) Hz region). Both constant-current mechanisms -similar to the mechanism o f the conventional unipolar detector- rely on the increasing withdrawa l of electrons from their reactions with increasing concentrations of analyte molecules and carrier cations.