Saturation region of helium ionization detector for gas-solid and gas-liquid chromatography

In the saturation region of the helium detector field intensity, the detector response is independent of the electrical field. In this region (at applied potential between 200 to 2000 volts per centimeter of electrode surface) the detector is operated at a low background current, and a low noise level, but it still exhibits a stable and sensitive response. The detector in this region can be operated with high purity grade helium without any further elaborate purification processes to yield a positive response to all compounds and gases tested. The operation of the detector in this mode has been adapted to both gas-solid and gas-liquid chromatography, with temperature programming. A sample can be introduced to the column via a gas sampling injection valve or via a syringe by direct injection into a modified injection port. The detector response is linear over a range of 10/sup 6/ units with a detection limit in the picogram range for organic compounds. 11 figures.