Determination of ethylthiometon residues in evironmental samples by gas chromatography/mass spectrometry

Abstract

A gas chromatography/mass spectrometric (GC/MS) procedure has been developed for the determination of ethylthiometon (ETM), which is a representative organophosphorus pesticide, in environmental samples. A liquid-liquid extraction method with dichloromethane (CH₂Cl₂) is applied to the separation of ETM residues in water samples. For sediment and fish samples, steam distillation is applied to the preseparation. The ETM in the distillate from a sediment sample is extracted with CH₂Cl₂. On the other hand, that from a fish sample is extracted with hexane and then is separated and purified by acetonitrile/hexane partitioning and alumina column chromatography. The extracts of water and sediment samples and the fraction of fish samples are concentrated and then determined by GC/MS, respectively. The detection limits are 0.12μg/l for water, 5.2μg/kg for sediment, and 5.6μg/kg for fish. The average recoveries of ETM from spiked water (0.8ppb) samples is 105%. Those from spiked sediment (40ppb) and fish (40ppb) samples are 90% and 85%, respectively. This method enables the reliable determination of ETM residues in environmental samples at ppb level.