LC-MS/MS Quantitative Method for Trace Analysis of Pesticides in Urban/Suburban Water Wells in Milwaukee, Ozaukee, Washington, and Waukesha Counties in Wisconsin

Abstract

The aim of this study was to develop a LC-MS/MS analytical method to quantitate aselection of pesticides that included: 2,4−dichlorophenoxyacetic Acid (2,4-D), carbaryl, dicamba, imidacloprid, malathion, 2-methyl-4-chlorophenoxyacetic acid (MCPA), and methylchlorophenoxypropionic acid (MCPP). Chromatographic and mass spectrum conditions were optimized by analyzing full scans, selected ion monitoring (SIM) scans, product ion (PI) scans, which developed a multiple reaction monitoring (MRM) scan. Additionally, a pretreatment and cleanup strategy was designed and optimized using liquid-liquid extraction. The method demonstrated acceptable mean percent recovery of 83.2% ±12.56% at a spiked level of 10 ng/mL. The developed quantitative method was applied to groundwater from 16 active, private wells located in the Milwaukee metropolitan area. There were eight wells that detected one or more of the targeted pesticides during four sampling events. Seven out of the eight pesticides were detected in June-July and August 2019.