Fully automated identification and quantification of five polar pesticides in groundwater by isotope dilution-online solid phase extraction coupled with high-performance liquid chromatography-quadrupole Orbitrap high-resolution mass spectrometry.

Abstract

A fully automated method for identification and quantification of five polar pesticides in groundwater by isotope dilution-online solid-phase extraction (SPE) coupled with high-performance liquid chromatography-quadrupole Orbitrap high-resolution mass spectrometry was developed. After one step of filtration, an aliquot of a 7.5-ml water sample was automatedly preconcentrated and purified on a turbulent Cyclone SPE column. The analytes were eluted in backflush mode, then separated on an analytical column and acquired by full MS/dd-MS2 scan in negative and positive ions mode. The major parameters for sample loading, cleanup, and elution were optimized in detail. Preconcentration and ionization efficiency were highly improved by using 0.1% acid solution in the mobile phase. The method provided good linearity of calibration coefficients (R2 > 0.995), sensitive method limits of detection (0.5-10.0 ng/L), accurate mass spectra (within 5 ppm error), satisfactory matrix spiking recoveries (98.4% to 109%), and high precision (intraday/interday relative standard deviations 1.57-8.90%). The method was successfully applied to analyze large batch groundwater of National Groundwater Monitoring Project and suspect screening of potential pesticides in groundwater. The study provided a practical alternative for a simple, robust, sensitive, and accurate identification and qualification of five polar pesticides in groundwater.