Pesticide residue testing of grains and oil seeds: Minimizing false positives and false negatives

Abstract

GC-MS based pesticide residue testing in grains often results in enhanced response, with the degree of enhancement being dependent on the type of grain. Some grain matrices cause matrix interference, leading to false positives and false negatives, as well as significant limitations in limits of detection (LOD) and quantification, particularly when published multiple reaction monitoring (MRM) assays are used without validation. Matrix-matched standards and analyte protectants are used routinely in pesticide analysis to combat enhancement and suppression, and to provide a more accurate indication of the residue levels present. Certain pesticide and matrix combinations are well known for illustrating the problems listed above.1,2 It is important to remember that published MRMs should only be used following validation to demonstrate that they are free from matrix interference in the matrix system under study