The GERSTEL Twister® enables efficient extraction of organic compounds from aqueous matrices based on Stir Bar Sorptive Extraction (SBSE). 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. 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. Labor- and resource-intensive sample preparation steps are eliminated. 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 Twicester® offers a simple possibility to position one or more Twisters magnetically on the inner wall of a sample vial for more efficient sample extraction. The Twicester 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.
Twister Sorbent Phases:
|PDMS Twister||EG/Silicone Twister|
|Phase||Polydimethylsiloxane (PDMS)||Polydimethylsiloxane (PDMS) / Ethylene glycol (EG) – copolymer on an inert metal grid for mechanical stabilization|
|Enrichment||Unspecific sorption of apolar compounds|
log(Kow) > 4
The polarity range can be extended by adding salt to the sample (salting out).
|Unspecific sorption of apolar compounds, additionally specific binding of polar hydrogen bond donors, such as phenols|
|Application examples||Pesticides in water|
PAH in marine tissue
2,4,6-TCA in wine
Flavor compounds in food
|Flavor compounds in beverages|
When the SBSE-step has been completed, the Twister is transferred to either a Thermal Desoption 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 desorptions can be performed for each GC/MS run resulting in even higher sensitivity and lower limits of detection.
Involatile, polar or thermally labile compounds can be extracted from the Twister with a solvent using TwisterBackExtraxtion TBE for subsequent determination by LC/MS.
- 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 labor
- Thermal desorption and GC/MS analysis are performed in one automated system