Computer evaluation of gas chromatograms with wide dynamic range

Summary

If the complete dynamic range of the flame ionisation detector (FID) amplifier signal is to be integrated during trace analysis, the computer used for this purpose must have an effective dynamic range of at least six decades. The detection limit for traces in the ppm range (parts per million), whilst the major component is simultaneosly integrated, is discussed using samples of pure styrene, propylene and vinyl chloride. The dynamic range can be increased by using minor components as internal markers, by a computer-controlled attenuator switch and by a splitter which produces an internal marker in the chromatogram. In this way, trace components around the ppm level can be determined with standard deviations of a few percent.