Determination of pesticides in washing waters of olive processing by gas chromatography-tandem mass spectrometry.

A simple and rapid SPE-GC method for the determination of 30 organochlorine, organophosphorus, and organonitrogen pesticides at ng/L levels in washing water of olive processing has been developed. Twenty-nine samples of water were collected directly in the inlet and outlet of the washing machines of three olive mills at various locations in Spain. Preconcentration and clean-up were performed by elution of the pesticides from a C18 SPE cartridge using dichloromethane. The target compounds were determined in the final extract by GC-MS/MS. The most frequently encountered pesticide residues were terbuthylazine, simazine, and diuron. In some of the water samples, coming from the inlet of the washing machines, terbuthylazine and diuron concentrations were above the maximum residue limit.