Stir bar sorptive extraction (SBSE) was introduced 1999 by Baltussen et al. [1]. This new sorptive extraction technique bases on the same principles than solid phase microextraction (SPME), but instead of a polymer-coated fibre, stir bars 10 mm long coated with 24 μl PDMS (Twister, GERSTEL) are used for enrichment of organic contaminants from aqueous matrices. Due to the much lower phase ratio (volume of water phase divided by the volume of the PDMS phase) compared to SPME, higher recoveries can be obtained by SBSE. Analogous to SPME, coated stir bars can be desorbed thermally with subsequent gas chromatographic analysis.
An approach of interfacing SBSE to liquid chromatography has been described recently [2]. In this case, the desorption of the extracted analytes was performed using a small volume of acetonitrile (ACN) or an ACN-water mixture. An aliquot of this desorption solution was then analyzed by HPLC.
In this study we describe the possibility of automation of the SBSE desorption step with direct transfer of the liquid extract to HPLC by use of the GERSTEL-MultiPurposeSampler MPS 3 (Twister Back-Extraction). For this purpose the MPS 3 was equipped with a temperature-programmable agitator and a special software. Using this procedure, after extraction of water samples by SBSE, the only manual step is the removal of stir bars from the sample vial and transfer to 250 μl glass inserts placed inside 2 ml autosampler vials. The MPS 3 then adds the ACN-water mixture to the stir bar, transports the vial to the agitator, where it is agitated at a defined temperature during the preset desorption time and fi nally withdraws an aliquot of the extract, which is injected into the HPLC.
