The Analysis of Polar Ionic Pesticides by Ion-Exchange Chromatography: The Possible Solution to a Long-Standing Problematic Analysis?

Polar ionic pesticides, such as glyphosate, chlorate, perchlorate and the like, often occur as residues in food, but are not always included in pesticide monitoring programs, simply because they are not ‘amenable’ to generic multi-residue methods. The introduction of the Quick Polar Pesticides (QuPPe) Method by the European Reference Laboratory for single residue methods (EURL-SRM) has enabled more laboratories to conduct analysis for at least some of the polar pesticides. Still, the absence of a liquid partitioning step, or clean-up step, results in ‘dirty extracts’ containing high concentrations of matrix coextractives. Thus, the separation and accurate quantification of analytes in QuPPe extracts is challenging. Analysts attempt to mitigate these issues by analyzing a single extract a number of times, using different chromatographic columns and conditions. These separation conditions are often less than ideal and the large amounts of coextractives often contaminate the low capacity columns to cause variation in retention time and a
decrease in the ruggedness of the method.