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A new analytical method is proposed for determining 34 multi-class pesticides in drinking and natural (ground, surface and sea) waters. The method combines the advantages of solid-phase microextraction (SPME) and gas chromatography-tandem mass spectrometry (GC-MS-MS). Polydimethylsiloxane (PDMS) and polydimethylsiloxane/divinylbenzene (PDMS/DVB) stationary phases were evaluated and the 99 ORDER REPRINTS optimization of the main extraction parameters was carried out in order to improve sensitivity and selectivity. That is the case of the influence of agitation, adsorption and desorption times, desorption temperature, addition of electrolytes, and pH of the sample. Performance characteristics of the analytical method were evaluated in order to validate the proposed methodology. Quantification limits were lower than 35.5 ng L 21 in all cases and therefore, the method can be applied for determining the target pesticides in drinking waters at concentrations below the levels allowed by EU and US legislation (100 ng L 21 ). The calibration was performed between 50 and 500 ng L 21 using linear or polynomial mathematical functions. Recovery rates (between 80.7% and 110.0% in all cases), and precision (,15.2% in all cases, expressed as relative standard deviation) were studied too. The method was applied to the analysis of natural and drinking water samples from the south-east of Spain, an intensive agricultural area. Pesticides most detected were endosulfan and lindane at concentrations that, in general, were lower than 100 ng L 21 .

A simple and reliable method using on-line purge and trap gas chromatography mass spectrometry has been developed for the determination of the fumigant 1,3-dichloropropene (1,3-DCP) in agricultural water and soil samples. The proposed analytical methodology was validated in the target environmental matrices by the analysis of spiked blank matrix samples. Limit of detection values of 0.05 microg/L for water and 0.005 microg/Kg for soils were obtained, while limits of quantitation were of 0.1 microg/L for water and 0.01 mg/kg for soils. Good recoveries (93-104%) and precision values (< 6%) were obtained for the target compound in the studied matrices. This methodology has been successfully applied to the analysis of incurred groundwater samples from an agricultural area, The Campo de Dalías (Almería, South Spain), although 1,3-DCP was not detected. The method was also applied to soil samples from greenhouse treated with a soil fumigant containing 1,3-DCP.