The Gerstel-Twister allows analysis of organic compounds from aqueous matrices by Stir Bar Sorptive Extraction (SBSE):
Faster than conventional liquid/liquid extraction techniques, and omitting time/cost preparation steps and solvents and up to 1000x more sensitive than SPME. The GERSTEL-Twister looks like a conventional magnetic stirring rod, and works the same; except for one small difference: While stirring, it adsorbs and concentrates the organic contents onto its sorbent coating. It makes no difference if the carrier solution is drinking or waste water, body fluids or beverages. After extraction, the Twister may be washed in UHQ water to remove not truly absorbed material. Finally the Twister is transferred to the TDU/TDS for direct GC analysis or to back extraction for LC analysis (see below)
|PDMS Twister||EG/Silicone Twiste|
|Phase||Polydimethylsiloxane (PDMS)||Polydimethylsiloxane (PDMS) / Ethylene glycol (EG) – copolymer on an inert metal grid for mechanical stabilization|
|Enrichment||Unspecific binding of apolar compounds
log(Kow) > 4
The polarity range can be increased by adding salt
|Unspecific binding of apolar compounds, additionally specific binding of polar hydrogen bond donors, e.g. phenols|
|Application examples||Pesticides in water
PAH in marine tissue
2,4,6-TCA in wine
Flavor compounds in food…
|Flavor compounds in beverage|
Twister's special feature: After extraction, it can be directly transferred to the Thermal Desoption Unit TDU or to the Thermal Desorption System TDS. This means that the thermal desorption, chromatography and subsequent detection of the organic compounds adsorbed on the PDMS coating are performed directly from the Twister.
Non volatile or thermally unstable compounds can be extracted from the Twister by TwisterBackExtraxtion (TBE) and subsequently analyzed by LC or LC/MS. Both the addition of solvent, extraction and injection is fully automated.
The Twister has already proved itself in many different application fields, for example essence and perfume industries, and detection of environmentally harmful substances such as polyaromatic hydrocarbons and pesticides. Due to its mechanical stability Twister can also be used for outdoor applications and be shipped easily.