In addition, the sensitivity of the technique is limited, typically to concentrations in the ppm to ppt range. The technique is also a preferred technique when sample automation is required such as in a quality control method or in sample screening. Thermal Desorption is routinely used for the analysis of volatiles in environmental samples as well as food samples. This is important for the analysis of high water content samples such as food products and water samples. The Purge and Trap technique is more sensitive by at least a factor of 1000 over headspace techniques.
Typical sensitivity is in the ppb range.
By purging samples at higher temperatures, higher molecular weight compounds can be detected. However, the Purge and Trap technique requires more time for sample preparation and can not normally be automated. In addition, very light volatiles and gases will not be trapped on the adsorbent resins and therefore will be missed in the analysis. In this technique, volatiles and semi-volatiles can be thermally extracted directly from solid matrix samples without the use of any solvents or any other sample preparation. Its main disadvantage is the analysis of high water content samples which results in the extraction of water into the GC column which will form an ice plug when cyro-focusing is used.