Multi-residue analysis of 66 biocides in river water, river sediment and suspended solids samples by gas chromatography-mass spectrometry

A multi-residue method for the screening and analysis of 66 common pesticides from hydrological samples, including sediment, suspended solids and water is presented. The investigated pesticides belong to the following chemical classes: polychlorinated organic compounds, triazine- and chloroacetanilide herbicides, organophosphorous insecticides and miscellaneous. The method includes fluidized-bed and microwave-assisted extraction for solid samples and solid-phase extraction on C-18-cartridges for water samples, followed by a combined purification-separation step on adsorption chromatography using open silica gel columns. Two fractions were eluted separating the 66 analytes into the non-polar and the more polar compounds. All analytes were identified and quantified by gas chromatography coupled with mass spectrometry in selected ion monitoring mode. The method was characterized by recovery experiments and statistical methods and finally applied to environmental river samples during a one-year monitoring program. This method allowed the screening and measurement of the contaminants in all parts of Liao-He and Yangtse rivers (Eastern China) at levels as low as 0.07 ng/L resp. 0.7 ng/L for hexachlorobenzene, with a precision better than 20%.