0.2 micron stainless steel guard column

An 8-minute reverse-phase acquisition method was optimized for detecting 31 pesticides, 4 class specific stable isotopes, and 2 internal standard instrument controls by manual infusion using positive mode electrospray ionization. Analytes were resolved and detected with a Shimadzu Nexera 30AD UPLC coupled to an API Sciex 6500 triple quadrupole mass spectrometer (Sciex, Redwood City CA). Optimized analyte precursor and product ions, declustering potentials, collision energies, and retention times are shown in Table 1. Global source parameters were optimized for sensitivity by injection over the UPLC gradient on the API Sciex 6500 in multiple reaction monitoring mode using the instrument settings shown in Supplemental Table S3. Pesticides were separated on a Shimadzu 30AD UPLC system in 8 minutes at a flow rate of 0.350mL per minute on a 2.1 x 150mm, 2.7µm Ascentis Express C18 column (Supelco) fitted with a 0.2-micron stainless steel guard column (Waters Corp), at 35°C. The mobile phases were A: 10mM ammonium formate and 0.1% formic acid in LCMS grade, 0.2 micron filtered Optima Water, and B: 10% isopropanol in LCMS grade acetonitrile, 0.2 micron filtered. The UPLC gradient and instrument module parameters are presented in Supplemental Table S4.