Analysis for N-Methylcarbamate Pesticides by High Performance Liquid Chromatography in Environmental Samples

Abstract

This method was developed for the routine analysis of ten N-methylcarbamate pesticides in environmental aqueous and soil samples. Aqueous samples are extracted with dichloromethane, while soils are extracted with acetonitrile. The extracts are solvent exchanged to methanol prior to analysis. Analysis entails a high pressure liquid chromatographic separation on a C18 reverse phase column, post column derivatization and monitoring the resulting fluorophore by fluorescence detection. The standard derivatization procedure is based on alkaline hydrolysis of the N-methylcarbamate to yield methylamine, which in turn is reacted with o-phthalaldehyde (OPA) and 2-mercaptoethanol to form 1-(2-hydroxyethylthio)-2-N-methylisoindole. For routine quantitation the product is excited at 340 nm and the fluorescence emission detected through a 418 nm cut-off filter. Initial laboratory data indicate that method detection limits, precision and accuracy should be reasonable for routine environmental samples. The detection limits for clean water samples are estimated to be in the 1 to 10 ug/L range, while soil samples are estimated to be in the 10 to 50 ug/Kg range.