Comparison of Sensitivity of Headspace GC, Purge and Trap Thermal Desorption and Direct Thermal Extraction Techniques for Volatile Organics

John J. Manura and Santford Overton, Scientific Instrument Services, 1027 Old York Rd, Ringoes, NJ 08551

Poster Number - 021P

The technique of Headspace GC was compared to conventional purge and trap thermal desorption and also to the direct thermal extraction (DTE) technique in order to determine the relative sensitivities of these techniques for the analysis of volatile organics.

Three different samples were studied via these techniques in order to determine the range of volatiles that could be detected via the technique as well as the relative sensitivity of each of the techniques at the various range of volatiles of the organic compounds. The first sample analyzed were olive oils. For headspace analysis, 5.0 ml of oil were used. In the purge and trap technique 1.0 ml of oil was used and was purged at 40 ml per minute for 30 minutes to purge the volatiles from the oil and trap them on a Tenax® TA thermal desorption trap. For the direct thermal extraction technique, 10.0 ul of the oil was injected directly onto the Tenax trap and subsequently thermally desorbed into the GC for analysis. The DTE technique proved to be 100 times more sensitive than the purge and trap technique and was able to detect a wider boiling point range of volatiles than the other techniques. The DTE technique was about 1000 times more sensitive than the headspace technique in addition to detecting a much higher range of volatile organics. In addition black tea and gasoline residues in soil were studied to compare these sample matrices via the same three GC injection techniques.

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