Improvement of the detection limit in capillary gas chromatographic trace analysis of C-2-C-4 hydrocarbons by post column cryogenic trapping

A method for the improvement of signal-to-noise ratios and hence detection limits in capillary gas chromatographic trace analysis of C-2-C-4 hydrocarb ons was developed. It is based on the post column cryogenic trapping of the separated hydrocarbons using liquid nitrogen as coolant and its fast reinj ection into the detector by rapid heating of the capillary tubing used for trapping. The improved signal-to-noise ratios were applied to decrease the sample volume and/or to lower the detection limit 10 to 27 times. The conce ntrations of these hydrocarbons in an urban air sample determined without a nd with post column cryogenic trapping were in good agreement but the preci sion was better when applying the cryogenic trapping mode.