Headspace Extraction or Purge and Trap

For the analysis of trace quantities of analytes, or where an exhaustive extraction of the analytes is required, purge and trap, or dynamic headspace extraction, is preferred over static headspace extraction. Like static head-space sampling, purge and trap relies on the volatility of the analytes to achieve extraction from the matrix. However, the volatile analytes do not equilibrate between the gas phase and matrix. Instead, they are removed from the sample continuously by a flowing gas. This provides a concentration gradient, which aids in the exhaustive extraction of the analytes. 

In general, the trap should do the following retain the analytes of interest, not introduce impurities, and allow rapid injection of analytes into the 

Weak Sorbent Medium Sorbent Strong Sorbent 

The transfer line between the trap and the GC is made of nickel, deactivated fused silica, or silica-lined stainless steel tubing. Active sites that can interact with the anlaytes are eliminated on these inert materials. The line is 

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