Extraction via Twister (SBSE)
Twister® is a registered
trademark of GERSTEL
GmbH & Co. KG

Twister / Stir Bar Sorptive Extraction SBSE

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

GC-Analyis:

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.

LC-Analysis:

Involatile, polar or thermally labile compounds can be extracted from the Twister with a solvent using TwisterBackExtraxtion TBE for subsequent determination by LC/MS.

 

Advantages:
  • 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

 


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