Identification and Quantification of 77 Pesticides in Groundwater Using Solid Phase Coupled to Liquid−Liquid Microextraction and Reversed-Phase Liquid Chromatography

This paper describes a method for the extraction, separation, identification, and quantification of 77 pesticides (neutral, acidic, and basic) including some s-triazine metabolites. The method is appropriate for organically (e.g. with humic acids) highly loaded groundwater samples. A comparative study of a pH-controlled mixed solid phase (LiChroprep RP18/LiChrolut EN) extraction with different desorption solvents (acetonitrile or acetonitrile and dichloromethane/methanol) is elaborated. A subsequent liquid−liquid microextraction reduces matrix effects. The pesticides in the sample are separated using RP-HPLC, detected, and identified by diode array. The efficiency is illustrated on a natural groundwater sample from a phreatic aquifer.