One of the most important aspects of reducing pesticide exposure is monitoring of pesticide residues in foods. A number of analytical methods have been developed, many of them based on traditional liquid-liquid extraction in combination with GC-MS or LC-MS. The QuEChERS (quick, easy, cheap, effective, rugged, and safe) sample preparation methods have been developed to help monitor pesticides in a range of food samples [1]. The dispersive Solid Phase Extraction (SPE) used to clean up these extracts can leave co-extractants, which can result in interferences such as ion suppression with the analytical results.

Stir bar sorptive extraction (SBSE) is a sorptive extraction technique based on polydimethylsiloxane (PDMS) coated stir bars. SBSE was developed to concentrate nonpolar analytes from aqueous solutions, and has recently been shown to effectively extract and concentrate PAHs from QuEChERS extracts while eliminating matrix interference for GC/MS analysis [2].

In this study we describe the potential benefi ts of using SBSE to concentrate pesticides from QuEChERS extracts and provide additional clean-up resulting in less matrix interference during LCMS/MS.