Gas Chromatography Detectors - Some Less Common GC Detectors > The Spark Discharge Detector > Page 85


The noise level was reported to be about 10 mV thus at a signal–to–noise level of 2 the minimum detectable concentration would be about 3 x 10-11g/ml. This sensitivity is comparable to that of the FID and the argon ionization detector. The detector was claimed to be moderately linear with a linear dynamic range of three orders of magnitude but values for the response index were not reported. It was not apparent whether the associated electronics contained non linear signal modifying circuitry or not. Unfortunately, there were several disadvantages to this detector. One disadvantage was the erosion of the electrodes due to "spluttering" In addition, the electrodes were contaminated by sample decomposition and it was essential that it was used with a well–controlled vacuum system.

The Spark Discharge Detector

Lovelock [15] noted that the voltage at which a spark will occur between two electrodes situated in a gas will depend on the composition of the gas between the electrode tips and suggested that this could form the basis for a GC detector. The system suggested by Lovelock is shown in figure 49.



Figure 49 The Spark Discharge Detector