Monitoring of pesticides in drinking and related waters in NE Spain with a multiresidue SPE-GC-MS method including an estimation of the uncertainty of the analytical results.

A new method, developed in an EC project (SMT4-CT96-2142) for the determination of 22 pesticides in drinking and related waters, has been used to analyze source and drinking water samples in the area of Barcelona (NE Spain). The procedure includes solid-phase extraction of water and subsequent analysis by GC-MS using few selected ions (SIR) in order to increase their sensitivity. The method was subjected to intra and interlaboratory tests and met the requirements of the EC Directive in terms of accuracy, precision and detection limit (0.025 microg/l range in water samples). A detailed analysis of the uncertainty sources of this method is included, which allows to estimate expanded uncertainties in the 10-20% range. The dominant sources of uncertainty are the solid-phase extraction procedure and the chromatographic quantification. Two triazine compounds, simazine and atrazine, are the main pesticides detected in wells of the Llobregat river and in water of the Ter river, respectively.