The analysis of volatile and semivolatile compounds in aqueous solutions using stir bar sorptive extraction (SBSE) as the extraction step is gaining acceptance in a wide variety of application areas including water, beverages and other consumer products. It has been shown to be simple, sensitive and often can eliminate cumbersome solvent extraction or other sample preparation steps.
Efficiency of analyte partitioning into the polydimethylsiloxane (PDMS) phase on the stir bar parallels the distribution of the analyte between octanol and water as described by the octanol-water partition coefficient Kow. The PDMS phase used for most SBSE is therefore well suited for extraction of nonpolar analytes. There is interest in enhancing the selectivity of this technique to allow analysis of more polar analytes, or to simplify the background from complex matrices.
Strategies have been developed to provide additional control of the partitioning of analytes into the PDMS phase during SBSE. Parameters such as sample pH, salt content and the presence of solvents during extraction can be used to enhance the extraction efficiency of a range of analytes including polar compounds. The very high capacity of the SBSE phase allows the use of solvent back extraction prior to thermal desorption to selectively reduce the background interference from complex sample matrices.
