Multiresidue analysis of three groups of pesticides in washing waters from olive processing by solid-phase extraction-gas chromatography with electron capture and thermionic specific detection

A multiresidue solid phase extraction-gas chromatography (SPE-GC) method is developed for the analysis of 28 organochlorine (OCPs), organophosphorus (OPPs) and organonitrogen (ONPs) pesticides at ng l− 1 levels in washing water from olive processing. Pesticides are separated from the water matrix, containing estimable amounts of olive oil, by eluting them from a C18 SPE cartridge using dichloromethane. The target compounds are determined in the final extract by gas chromatography using thermionic specific (TSD) and electron capture (ECD) detection. Recoveries range from 79% to 129% in spiked washing water samples and detection limits are between 1 and 4 ng l− 1. The method was successfully applied to determine OCPs, OPPs and ONPs in 25 samples of water collected directly in the inlet and outlet of the washing devices of three olive mills at different locations in Jaén (Spain). The most frequently encountered pesticide residues were terbuthylazine, simazine and diuron. In some of the water samples coming from the inlet of the washing devices, terbuthylazine and diuron measured concentrations were above the concentration limits scheduled by law.