Part per trillion level determination of isoproturon in certified and estuarine water samples with a direct optical immunosensor

An optical immunosensor coupled to a FIA system was developed and applied to monitor isoproturon in various types of water samples. The assay is based on a solid phase fluorescence immunoassay with immobilised analyte derivative and free, fluorescence labelled antiisoproturon antibodies. Cross-reactivities (CRs) of linuron, diuron and chlortoluron were carried out to assess the influence of structurally similar compounds on the response of the biosensor. The highest CR values were obtained for diuron, 93%, whilst chlortoluron and linuron showed values of 53 and 46%, respectively, at 0.1 mug l-1 of cross-reactant. Detection limits of 0.01 and 0.14 mug l-1 were achieved after the analysis of MilliQ and river water samples, respectively. The validation of the biosensor was carried out analyzing Aquacheck certified river samples which contain different amounts of phenylurea pesticides. This River Analyser (RIANA) prototype with an optical immunosensor can be applied for monitoring of isoproturon in natural river water samples. Individual assays are completed within 15 min including total regeneration of the transducer.