Development and validation of residue methods for the determination of the pyrethroids lambda‐cyhalothrin and cypermethrin in natural waters

This paper describes the development of methods suitable for the sampling and analysis of the pyrethroid insecticides lambda‐cyhalothrin and cypermethrin in natural waters. A solid‐phase water‐sampling method which avoids the requirement for transport and storage of large volumes of water is described. This method is shown to be capable of extracting trace levels (ng litre −‐1 ) of the title compounds from natural waters with efficiencies of at least 80%. Chromatographic analysis of processed samples by gas chromatography–electron capture detection enables determination of residues at levels of 1–2 ng litre −‐1 in water.