Sorbent and Analyte Recovery

To date, the only sorbent used reportedly for coating the stir bar is poly-dimethylsiloxane (PDMS), although the use of stir bars coated with polar sorbents is predicted for the future [141]. Using this sorbent, the primary mechanism of interaction with organic solutes is via absorption or partitioning into the PDMS coating such that the distribution constant [equation (2.37)] between PDMS and water (APDMs/w) is proposed to be proportional 

According to the theoretical development for this technique given in Bal-tussen et al. [141], 

In comparing the same compounds while using PDMS sorbent, recovery from aqueous solution by SBSE was demonstrated [141] to be greater than recovery by SPME. Tredoux et al. [146] noted enrichment factors for benzoic acid in beverages to be approximately 100 times higher for SBSE relative to SPME, and Hoffmann et al. [147] reported sensitivities 100 to 1000 times higher by SBSE than by SPME for the extraction of analytes in orange juice and wine. 

Extraction of aqueous samples occurs during stirring at a specified speed for a predefined time. After a given stirring time, the bar is removed from the sample and is usually thermally desorbed into a gas chromatograph. 

However, Popp et al. [148] desorbed extracted polycyclic aromatic hydrocarbons by ultrasonic treatment of the stir bar in acetonitrile or acetonitrile water mixtures in order to perform liquid chromatographic analyses of the extract. 

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