Fully Automated QuEChERS Clean up and LC/MS-QQQ Analysis of Pesticides in Fruits and Vegetables

This article outlines a fully automated method based upon the widely used QuEChERS (quick, easy, cheap, effective, rugged and safe) methodology -, for the extraction and clean up of pesticide residues in samples of fruit and vegetables. With the number these measurements set to rise in the near future, the commercial case for the automation of this time consuming, manual method is compelling.

The QuEChERS method uses an acetonitrile extraction followed by the salting out of water from the sample using anhydrous magnesium sulphate, sodium chloride and buffering citrate salts to induce liquid-liquid partitioning. This initial extraction is performed offline and provides a crude extract ready for QuEChERS clean up.

An automated dispersive solid phase extraction (DSPE) is conducted for clean up, using a combination of primary secondary amine sorbent (PSA) to remove fatty acids and anhydrous magnesium sulphate to reduce the remaining water in the extract. After mixing and centrifugation the upper layer is ready for analysis.

The determination of pesticides in fruits and vegetables is required to ensure food safety. Sample preparation is an important part of any multi-residue method. Automating the sample clean-up and coupling the robot directly to Liquid Chromatography Mass Spectrometry – Triple Quadrupole (LC/MS-QQQ) holds the promise of dramatic improvements in laboratory productivity by streamlining the analytical process and presents opportunities to improve data quality at the same time.

The methodology and hardware may be used in two different configurations, either as a stand-alone Robot performing the DSPE clean up in isolation, (i.e. not directly
coupled to LC/MS-QQQ), or alternatively in an special configuration, coupled directly to LC/MS-QQQ, providing the greatest levels of laboratory productivity available