Enrichment Coils use thermal modulation to enrich gas samples for quantifiable peaks. Consisting of a length of resistively heated wide bore capillary column, they can be used in a GC column oven or on a Model 110 detector chassis for nonchromatographic stream monitoring applications. Thermal modulation causes many analytes like toluene to adsorb on the enrichment coil until it is saturated and reaches equilibrium, usually a matter of seconds. Upon heating, the analytes desorb from the enrichment coil, producing a peak which can be easily measured, rather than a barely discernible shift in baseline level.
The chromatograms below show a nonchromatographic monitoring of a gas stream. In the first chromatogram, a slight baseline shift is the only clue that the concentration of the stream has changed. With the enrichment coil, the shift between 1ppm and 2ppm concentrations becomes obvious.