Of the sorption-based extraction techniques available today, sorptive extraction using stir bars (SBSE) has developed into an established sample preparation technique, for which hundreds of typical applications can already be found in the literature that forms part of almost all scientific disciplines. SBSE provides significant capacity for static micro extraction, together with an excellent performance in the ultratrace range, in particular during the analysis of complex systems. Furthermore, it is very effective and when compared to other alternative techniques, is easy to handle and offers a high degree of reproducibility.

Using the GERSTEL Twister, analytes from aqueous and other liquid matrices can be extracted by applying the principle of Stir Bar Sorptive Extraction (SBSE). The Twister consists of a magnetic stir bar encased in glass and coated with a sorptive phase (generally PDMS). During extraction, the Twister is inserted into the sample like a stir bar and a stirring action is initiated. The analytes from the sample are then distributed between the extraction phase, such as PDMS, and the liquid sample phase as in a liquid/liquid extraction and the components to be examined accumulate in the PDMS phase. The Twisters are then desorbed in one of the GERSTEL thermal desorption systems and the analytes are transferred to the gas chromatography column (GC column). Further sample preparation steps are not necessary.

Solid Phase Micro Extraction (SPME) is a solvent-free sample preparation technology. Since its introduction in the early 1990s, it has become a widely used technique for the extraction and enrichment of target analytes from a variety of matrices. It utilizes a coated fiber inside a syringe-like holder to extract and enrich volatile and semi-volatile compounds from a compound.

To extract the analytes from the sample, the coated part of the SPME fiber is either inserted directly into the sample solution or is held inside the headspace above the sample. In accordance with the laws of distribution and/or adsorption, the analytes will then accumulate in the coating. After the extraction step comes the desorption step. The purpose of that step is to release the analytes from the coating on the SMPE needle. This is generally performed thermally, without additional intermediate steps, in the injector of the gas chromatograph or by the eluent in the injector of a High Performance Liquid Chromatography (HPLC). All of the necessary steps can be automated using the GERSTEL MultiPurposeSampler (MPS).

The Thin Film Solid Phase Micro Extraction (TF-SPME) is an extension of the conventional SPME, whereby TF-SPME is more sensitive than the standard SPME due to its larger surface area and the larger phase volume, both of which give rise to an improved analyte yield. The film consists of a 20 mm x 4.8 mm carbon mesh sheet impregnated with a sorptive phase. This can be used in both headspace and immersion mode. In headspace mode, the film is suspended above a solid or liquid sample in a closed vial, while in immersion mode, it is inserted directly into a liquid sample. In both cases, the sample is stirred using a stir bar.

If the stir bar is replaced by a GERSTEL Twister, the Twister will ensure additional PDMS phase volume and, in combination with the TF-SPME, will improve the extraction efficiency. Once extraction has been performed, the Twister and the film are desorbed in one of the GERSTEL thermal desorption systems and the analytes are transferred to the GC column. Further sample preparation steps are not necessary.