188.8.131.52. Thermal desorption of volatiles
Thermal desorption is an approach that uses heat rather than solvents to remove trapped volatiles from the adsorbent packing material. During analysis, the packing material is heated in a temperature-controlled environment in the analytical instrument and the volatiles desorb off the collection surface into the column flow. Thermal desorption techniques are particularly advantageous for: 1) sampling volatiles emitted at very low concentrations, 2) identifying highly volatile chemicals that would co-elute with solvent during separation, 3) obtaining a rapid profile of the volatiles associated with an odour source, or 4) collection of volatiles in a static system with very limited or no air exchange. Thermal desorption also has certain disadvantages compared to solvent desorption. Because the entire sample is desorbed on column during GC analysis, each sample can be analysed only once. For various reasons, most thermal desorption techniques are not particularly well suited to quantification of volatile compounds. Methods of thermal desorption using SPME and Tenax cartridges are described in the following sections.