Design, Performance, and Applicability of a Newly Developed Sample Introduction System for Use with Stir Bar Sorptive Extraction (SBSE)

App Note 5/2002

The use of stir bar sorptive extraction (SBSE) as a technique to extract volatiles and semi-volatiles from polar, especially aqueous matrices, has gained more and more acceptance in several application areas. Thermal desorption, analogous to SPME, has been found to be the most suitable technique to transfer the extracted analytes into an analytical system and make them accessible for gas chromatographic analysis. PDMS coated stir bars („Twister“) have much more stationary phase and consequently bigger outer dimensions compared to SPME fibers. They do not fit into standard injection ports for thermal desorption as SPME fibers do, therefore usually a thermal desorption unit is used for this purpose. This type of unit is intentionally designed to desorb previously trapped analytes from porous polymer-packed sample tubes, or for thermal extraction of volatiles from solids. It works perfectly for Twister desorption, but may simply be somewhat oversized if this is the only purpose.This paper describes the design, performance and applicability of a new desorption unit especially designed for use with “GERSTEL Twister”. This unit is compatible with existing GC models and can be automated using a modified regular autosampler.