The extraction and clean-up procedures are important steps in targeted and semi-targeted methods for extension work to make feasible the inclusion of a wide range of target analytes such as addition of a growing number of new fungicides and insecticides that are newly marketed for protection of crops. In addition there is significant interest in examining degradation products or metabolites of active ingredients and safeners in pesticide control products. The extraction and clean-up procedures in targeted methods are often crucial in the detection of metabolites and obtaining sufficiently high recoveries. In this work we will present results from a variety of sample preparation methods used to target pesticides and their metabolites for simultaneous analysis to ensure high recovery, selectivity, and stability of metabolites or degradation products. These results will be discussed also in context to the feasibility of commonly tested solvents, such as methanol and ethanol with or without water and addition of additives including 0.1v% formic acid for untargeted analysis of metabolites. These untargeted methods often subsequently utilize reversed phase liquid chromatography – high resolution mass spectrometry with basic optimization of mobile phase and stationary phase conditions. Targets methods require the availability of standards such that chemical identifies can be verified in samples through typically four point criteria of verification, while untargeted methods utilize metabolomics workflows for identification of mass spectral tags or shifts in chemicals structure during metabolism that aids in structural elucidation. Additional MS spectral features that will be discussed include formation of adducts, isomers, and artifacts.  In this comparison targeted reversed phase liquid chromatography-tandem mass spectrometry methods utilize for analysis of pesticides and metabolites in pollen, beebread, and atmospheric samples will be discussed to illustrate the impact of extraction solvents and chromatographic separation conditions on frequency of detection of challenging active ingredients, degradation products and more specifically metabolites. These conditions will be compared to those typically used for untargeted methods for metabolites of ingredients in pesticide formulations.

Targets methods for analysis of an extended range of pesticides and their metabolites and future needs and comparability to untargeted analysis

ACS Fall 2021

The official archive and repository for all ACS Meetings & Expositions abstracts and select posters or presentations.