A method for the simultaneous extraction of seven pesticides from soil and sediment

Organic pesticides are difficult compounds to extract from soils and sediments due to their strong affinity for soil particulates. Different pesticide compounds migrate to varying extents in the environment depending on their chemical structures, with effects ranging from strong adsorption to soil particles to rapid dissolution in water. Published methodologies report procedures for extracting and analysing discrete compounds or chemical classes but there is a lack of previous work concerned with methodologies for the simultaneous extraction and analysis of organic pesticides from different chemical classes. The soil environment is a complex matrix and farmers use a variety of compounds for pest control; with regular crop rotation a diverse mixture of chemicals is likely to be present in arable fields. Mindful of a legacy of pesticide contamination in water and the requirement for management of water resources at catchment scales there is a need to quantitatively assess the storage and transport of a variety of organic pesticides in different phases; soil, sediment and water. This paper describes a methodology for analysing seven different organic pesticides representative of five different classes of pesticide using a single methodology. Prior to use all glassware was deactivated using dimethyldichlorosilane to prevent adsorption effects. Soils then underwent a triple ultrasonication in acetone before being methylated with trimethylsilyldiazomethane. Final extracts were dissolved in hexane and analysed by GC/MS. Recoveries from the soil were determined to range between 70% and 114%.