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Last Update: 01/31/00

Direct Thermal Analysis using the SPTD System:
A New Technique To Permit the Analysis of Volatiles and Semi-Volatiles In Solid Samples Without Solvent Extraction

By John J. Manura and Santford Overton

One of the techniques which can be used with the Short Path Thermal Desorption System is known as Direct Thermal Analysis. The technique of Direct Thermal Analysis permits the analysis of solid samples without any prior solvent extraction or other sample preparation. The solid sample to be analyzed is inserted directly into the Glass Lined Stainless Steel (GLT) Thermal Desorption Tube between two quartz wool plugs. The Desorption Tube with the sample enclosed is purged with carrier gas to remove all traces of oxygen, after which the sample is heated to a predetermined set temperature and sparged into the GC injection port, where it is cryotrapped at the front of the GC capillary column. After trapping the volatilized components from the sample for a period of 5 to 10 minutes, the components are eluted from the GC capillary column via a temperature program cycle and are detected via a GC detector or mass spectrometer. This technique is useful for the analysis of a wide variety of solid samples including vegetation, packaging and building materials, food products, pharmaceuticals, and other manufactured products some of which are described below. The technique is useful for identifying trace residues of volatiles and semi-volatiles in these solid matrix materials. Normally, these samples would be analyzed after first extracting with a suitable solvent such as chloroform, ether, benzene, etc. The exposure of laboratory staff to these solvents has become of major concern to both employees and health officials. In addition the disposal of used solvents has become a serious problem and is rapidly becoming quite expensive.

The high recovery rates, time savings for sample preparation and the high sensitivity of Direct Thermal Analysis are the features which make this technique attractive to the analyst. Direct Thermal Analysis of solid samples using The Short Path Thermal Desorption System offers the following advantages:

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