Multi-residue analytical methods, in recent years, have grown in interest and value within industry, government, and other regulatory agencies worldwide. As regulations expand to target more pesticides at increasingly lower concentrations, the methodology used to detect these compounds in regulated products and commodities must advance accordingly. In this study, methodology was developed using liquid-chromatography/tandem mass spectrometry (LC-MS/MS) for the positive identification and quantification of 27 chemically diverse active ingredients (AIs). Some of these AIs, including glufosinate and phenoxyacid herbicides, proved challenging to incorporate into one single analytical method. The 27 compounds were, therefore, analyzed by two methods: one in positive ionization mode, and one in negative. An AB SCIEX X500B quadrupole time-of-flight (qTOF) mass spectrometer was used with high-resolution multiple reaction monitoring (MRM-HR) mode for the identification and quantification of these compounds. The methods were then used for a unique application: screening for these residues in extracts from agriculturally-used plastic film. Detectable concentrations (≥50 ng/g) of 5 of the 27 analytes then prompted the development of an easily implementable wash step to render the remaining residues lower than regulatory guidelines for plastic recyclability (≤50 ng/g). Although the objective of this study was specifically for plastics recycling, the value of this multi-residue method extends across residue analysis in food, water, and other commodities. Additionally, while qTOF provides the benefit of accurate mass determination for high confidence in compound identification, these methods could easily be transferred to nominal MS with MRM capabilities. This unique application is a valuable addition to existing multi-residue analytical methods currently available in the literature, and is amongst other published methods using accurate mass combined with MS/MS technology on this diverse group of chemicals for positive identification and precise quantification.

Development and application of two multi-residue analytical methods for the quantification of 27 active ingredients in recyclable plastic

ACS Fall 2021

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