Dynamic headspace gas chromatography: concentration of volatile components after thermal desorption by intermediate cryofocusing in a cold trap : I. Principle and applications

Abstract

The possibilities of dynamic headspace sampling for different applications in flavour and fragrance chemistry are demonstrated. A system for analysis of volatile components by means of the purge and trap technique with cryofocusing as an appropriate concentration method prior to capillary gas chromatography is described. Headspace components are concentrated on Tenax TA, thermally desorbed and intermediately trapped in a ”retention gap“ (cold trap), cooled to  130°C and connected to the capillary column via a modern butt connector. Subsequently the retention gap is heated to 150°C in a few seconds. A characteristic feature of the system is that during the desorption step the by-pass vent of the interface between the “retention gap” and the fused-silica capillary column can be opened, allowing the components to desorb at high flow-rates, i.e., on the one hand a sensitivity gain can be obtained as larger desorption volumes can be analysed and on the other a more complete and reproducible recovery of mid-and high-boiling compounds is possible. Simultaneous “sniffing” and flame ionization detection are practicable-by installing a commercially available effluent splitter at the end of the capillary column. Thus, the correlation of analytical and sensory data is available. The performance of this laboratory constructed system is demonstrated by applications to flavour and fragrance components.