An Automated Technique for Fast, Ambient Temperature Extraction and Analysis of Multi-Residue Pesticides in Various Matrices

Monitoring for Contaminants in Foods & Beverages
Oral Presentation

Prepared by R. Addink, T. Hall
Toxic Report LLC, 580 Pleasant St, Watertown, MA, 02472, United States


Contact Information: [email protected]; 617-393-1713


ABSTRACT

Recent years have seen an increased interest in the analysis of agricultural products and foods with regards to pesticides. Although not regulated extensively by the US federal authorities (FDA, etc), a number of methods has been developed for quick and effective screening of matrices for multiclass and multiresidue analysis (QuEChERS). Similarly legalization of medical (29 states) and recreational (8 states) marijuana has created concern for consumer safety of cannabis products and led to demands for pesticides testing.

Automation of such methods can greatly enhance laboratory efficiency, and provided with the right tools, lead to same day sample analysis with greater accuracy and reproducibility. Pressurized Liquid Extraction (PLE) is an automated technique for extraction of complex matrices, typically done at 100-120 oC, 1500 psi and a duration of 20 min. Work presented here focused on berries, coffee, roots, seeds and tea as foods and also on cannabis. Goal was to develop a convenient method to analyze between 120-200 pesticides via ambient temperature extraction.

Extraction cells were filled with inert material, sample aliquots, FMS CleanXtract™ and spiked with relevant standards. Cells were sealed and loaded onto the PLE extraction system. Cells were filled sequentially with acetonitrile, pressurized and held at ambient temperature for 5-10 minutes. The cells were then depressurized and flushed with nitrogen to purge remaining solvent into the collection tubes. From the final extract an aliquot was transferred to a vial for GC/MS analysis.

Excellent recoveries were seen for 203 pesticides from 9 individual mixes for the foods. Performance of in-cell clean-up using traditional SPE sorbents proved to be highly efficient at removing non-target interferences. The process of performing the clean-up in-cell required no additional sample prep steps to be employed thus enabling a true one step automated extraction. Analysis of cannabis extracts (spiked at 0.1 ug/g) showed very good recoveries of an extensive list of pesticides ranging across multiple chemical classes. Reproducibility of the extract sets yielded good RSDs for most analytes. Method Detection Limit study results will also be presented.