Ultra-High Performance Liquid Chromatography/Electrospray Ionization-Tandem Mass Spectrometry Determination of 151 Pesticides in Soybeans and Pulses

Abstract

This paper presents the application of ultra-high performance LC (UHPLC) and MS for the determination of 151 pesticides in soybeans and pulses. A core-shell particle (2.6 micro m particle size) column and a fully porous sub-2 microm (1.7 microm particle size) column showed comparable performance in chromatographic resolution and separation, increasing selectivity, and reducing analysis time. UHPLC was coupled with either a triple quadrupole mass analyzer (MS/MS) or a quadrupole Orbitrap (namely Orbital trap) mass spectrometer (Q-Orbitrap MS), which possesses fast data acquisition capability. Both configurations yielded analytical run times of < or =14 min. Soybean and pulse samples were analyzed and quantitated for pesticide residues using the QuEChERS (Quick, Easy, Cheap, Effective, Rugged, and Safe) procedure, UHPLC/electrospray ionization (ESI)-MS/MS, and matrix-matched standard calibration curves (in an analytical range of 5-500 microg/kg) with isotopically-labeled standards or a chemical analog as internal standards. The method performance parameters that included overall recovery, intermediate precision, and measurement uncertainty were evaluated according to a nested design experiment. Approximately 89% of the pesticides studied had recoveries between 81 and 110%; 95%, had intermediate precision < or =20%; and 93% showed measurement uncertainty < or =40%. From a pilot study of 100 samples, eight tested positive by UHPLCIESI-MS/MS for carbendazim, methomyl, or imidacloprid. These pesticides were further confirmed using UHPLC/ESI-Q-Orbitrap MS based on accurate mass measurement with mass error < or =5 ppm.