In citrus aqueous essences and distilled essence oils, some of the most volatile components are important contributors to the flavor and aroma of the mixture. However, because of their volatility, they are often the most difficult components to collect in the conventional manner during gas–liquid chormatographic (GLC) separation and to subsequently analyze (by mass spectrometry, for example) without losing the sample in the process. Combined GLC–mass spectrometers have overcome this difficulty to some extent, but there are many occasions when a combined GLC–mass spectrometer is not available. At times it is advantageous to collect volatiles from a complex mixture for analysis by mass spectroscopy and to collect less volatile compounds for some other determination (such as infrared) from a single GLC run.
Manuel G. Moshonas and Philip E. Shaw, "Trapping Volatiles from GLC for Injection into a Mass Spectrometer," Appl. Spectrosc. 25, 101-102 (1971)