Selection of Thermal Desorption and Cryo-Trap Parameters in the Analysis of Teas


John J. Manura, Scientific Instrument Services

The range of organics in a sample such as green and black teas can range from very light volatile gases to volatile and semi-volatile organics. The techniques available to analyze these samples include headspace GC, Purge and Trap thermal desorption (P&T TD), direct thermal extraction (DTE), solvent extraction and newer techniques such as solid phase micro extraction (SPME) and supercritical fluid extraction (SFE). Proper selection of the analysis technique as well as optimization of the system parameters is required to achieve the desired results. One of the best techniques to analyze food products for flavors is the Purge and Trap System combined with cryo-focusing of the analytes at the front of the GC column before analysis. Through the selection of the purge and trap sampling temperature, GC and thermal desorption system parameters and cryo-trap parameters the range of volatile and non-volatile organics that are analyzed can be selected. In this article we are utilizing samples of green and black tea via the Purge and Trap Technique (P&T) with the Short Path Thermal Desorption System (SPDT) to study the P&T parameters, thermal desorption parameters and cyro-trapping parameters which can be adjusted to selectively analyze a range of analytes in these samples. Through the selection of these parameters, data can be obtained similar to what would be received via other techniques such as multidimensional chromatography.