Electron capture detector for gas chromatograph

摘要

An electron capture detector has a detection cell containing an electrode and a radioactive isotope for ionizing a carrier gas and causing electrons to be emitted. Before the detection cell begins to be contaminated, a pulse voltage is applied to the electrode and the frequency of this pulse voltage is controlled by a loop control routine to find an initial pulse frequency value such that a current through the electrode due to the emitted electrons comes to have a specified current value as a carrier gas is introduced into the detection cell. When a sample is analyzed after the detection cell becomes contaminated, the same process is carried out before the sample is injected and a pre-measurement pulse frequency value is obtained. After the sample is injected, the same process is repeated to obtain a measured pulse frequency value. The concentrations of components of the sample are calculated from the measured pulsed frequency value, and the effects of contamination of the detection cell are removed by considering both the initial and pre-measurement pulse frequency values.