Determination of the 1‘<i>S</i> and 1‘<i>R</i> Diastereomers of Metolachlor and <i>S</i>-Metolachlor in Water by Chiral Liquid Chromatography−Mass Spectrometry/Mass Spectrometry (LC/MS/MS)

Abstract

An enantioselective method for the separation and quantification of the diastereomer pairs of metolachlor and S-metolachlor in surface and ground waters is presented. Samples are purified and concentrated using a C18 (octadecyl silica) solid-phase extraction (SPE) procedure and analyzed by chiral column liquid chromatography-mass spectrometry/mass spectrometry (LC/MS/MS) interfaced with either atmospheric pressure chemical ionization (APcI) or atmospheric pressure photoionization (APPI) sources. The overall mean percent procedural recoveries (percent relative standard deviations) are 89% (10.6%) for surface water and 80% (9.1%) for ground water. The method limit of quantitation (LOQ) is 0.10 ppb. The method validation was conducted under U.S. EPA FIFRA Good Laboratory Practice Guidelines 40 CFR 160.