PRODUCT FOCUS: GERSTEL Twister®
Stir Bar Sorptive Extraction (SBSE) is a solvent-free extraction technique, which is significantly faster than most conventional extraction techniques. SBSE is up to 1000 x more sensitive than SPME since the stir bar has significantly more sorbent volume and since it can extract, and concentrate analytes from, a much larger sample volume due to the efficient stirring. Therefore, this edition of PRODUCT FOCUS takes a look at the GERSTEL Twister®, an instrument which enables efficient extraction of organic compounds from aqueous matrices based on SBSE.
The Twister may look like a conventional magnetic stirring rod, but while it stirs samples, such as water, body fluids or beverages it absorbs and concentrates organic compounds into its sorbent coating. A large number of samples can be extracted simultaneously using multi-position stir plates resulting in high productivity and throughput.
Labour- and resource-intensive sample preparation steps are eliminated by the GERSTEL Twister. Analytes are typically desorbed from the Twister using thermal desorption. Liquid desorption using a solvent can be performed whenever the analytes are very high-boiling, thermally labile, or when they must be determined by HPLC.
The GERSTEL Twister® also offers the possibility of positioning one or more Twisters magnetically on the inner wall of a sample vial for more efficient sample extraction. The Twister® approach enables the extraction of a sample using more Twisters simultaneously, for example using Twisters with different types of phases for a more complete combined extraction and improved analyte recovery.
GC-Analysis
When the SBSE-step has been completed, the Twister is transferred to either a Thermal Desorption Unit TDU or a Thermal Desorption System TDS. Thermal desorption and GC/MS determination of the concentrated organic compounds are then performed in one integrated system under integrated software control. Using the multi-desorption mode, multiple Twister desorption’s can be performed for each GC/MS run resulting in even higher sensitivity and lower limits of detection.
LC-Analysis
Involatile, polar or thermally labile compounds can be extracted from the Twister with a solvent using Twister Back-Extraction TBE for subsequent determination by LC/MS.
Benefits of the GERSTEL Twister
- Up to a 1000 times lower detection limits than SPME
- Quantitative, with large linear range
- A large number of samples can be extracted simultaneously for highest productivity
- Requires minimal time and labour
- Thermal desorption and GC/MS analysis are performed in one automated system.
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