Development of a photochemically induced fluorescence-based optosensor for the determination of imidacloprid in peppers and environmental waters

A novel flow-through solid phase spectroscopic assembly implemented with photochemically induced fluorescence (PIF) has been developed for the rapid, sensitive and selective determination of imidacloprid. The pesticide is derivatized on-line by irradiation with ultraviolet light providing an intensively fluorescent compound. The determination is carried out by measuring the fluorescence intensity of the photoproduct once retained on C18 silica gel filling the flow-cell. The method proposed has been applied to the determination of imidacloprid in natural waters and peppers. The quantification limit (QL) (0.015 mg kg−1) in peppers was lower than the maximum residue limit (MRL) established by Spanish Legislation (0.5 mg kg−1). The method also seems to be suitable for environmental water analysis providing satisfactory recoveries (94.0-108.6%). The results obtained in the analysis of real samples are in good agreement with those provided by a reference liquid chromatography (HPLC) method.