Flow-through photochemically induced fluorescence optosensor for the determination of linuron

This manuscript presents the development of a new photochemically induced fluorescence flow-injection system, combined with solid-surface adsorption, for the determination of the benzoylurea pesticide linuron. The determination is carried out by measuring the fluorescence intensity of a photoproduct, formed by on-line irradiation with ultraviolet light, and retention on a solid matrix filling the flow-cell. The procedure is developed in the presence of two surfactants: sodium dodecyl sulphate and hexadecyltrimethylammonium chloride, which are critical for the detection of the fluorescence emission in the solid surface. The possible interactions between the linuron photoproduct, the micellar medium employed and the solid support (C18 silica gel) are discussed. Parameters related to the analytical signal and to the FIA manifold are optimized. Finally, the feasibility of the developed method was tested by the determination of linuron in both environmental and drinking water samples. Determinations at μg L−1 level were accomplished after a solid-phase pre-concentration procedure.