QuEChERS Method for Pesticide Residue Analysis

Quenchers are used to diminish fluorescence intensity, thereby improving the detection of specific pesticides. In pesticide analysis, the quenching mechanism involves dynamic or collisional quenching. Here, the quencher and the pesticide molecule collide, causing energy transfer and reducing fluorescence intensity as a result. They minimize background fluorescence and unwanted signals that may interfere with accurate pesticide detection. This is particularly important in fluorescence-based detection methods, where the presence of quenchers can help improve the signal-to-noise ratio and the overall accuracy of the analysis.

The Quenching Process in Two Steps

1. Extraction

• Solvent extraction techniques are designed to achieve maximum yield of analytes from the base matrix.
• Solvent selection is important to minimize co-extracting compounds.
• Analytes are extracted from the matrix with acetonitrile and salts/buffers.

2. Cleanup

• Sample cleanup is necessary to reduce interferences.
• Interferences can damage analytical instrumentation and complicate analyte identification and quantification.
• The use of PSA, C18, GCB (Graphitized Carbon Black) or Z-Sep sorbents allow removal of sugars, lipids, sterols, organic acids, proteins, carotenoids, chlorophyll and other pigments prior to a GC-MS/MS or LC-MS/MS analysis.

1. Homogenize sample
2. Transfer sample to 50mL tube
3. Add ACN and internal standard and shake for 1 min
4. Extraction: Add extraction salts and centrifuge (55227-U for EN15662:2008 and 55234-U for 2007.01 AOAC)
5. Cleanup: Transfer supernatant to cleanup tube
6. Shake and centrifuge
   a) LC-MS/MS Analysis: Dilute extract with mobile phase
   b) GC-MS analysis: Analyze directly or after solvent exchange

The specific choice of quencher and its concentration will depend on the analytical method and the pesticides being targeted for detection.

Methods for Pesticide Analysis

EN 15662 QuEChERS Method

This method is a sample preparation technique used for the analysis of pesticide residues in food samples, including fruits, vegetables, and other food products.

AOAC 2007.01 QuEChERS Method

This method is used for the determination of pesticide residues in foods. Specifically, it is a multi-residue method for the analysis of over 300 pesticides and environmental contaminants in various food commodities.

QuEChERS Selection Guide

Products for the Extraction Step