Development of an automated controlled-pore glass flow-through immunosensor for carbaryl

The application of controlled-pore glass (CPG) as solid support for immobilization of immunoreagents in order to develop flow-through immunosensors is described. Monoclonal antibodies (MAbs) to carbaryl were site-directed immobilized on CPG through covalent attachment of their oxidized carbohydrate moieties to amine groups generated on the surface of silanyzed CPG. The automated immunosensor system is based on the LIB-CNA36 MAb in a direct competitive assay format, with horseradish peroxidase as enzyme label and fluorimetric detection. The dynamic range of the sensor is 0.05–1 μg l−1, with a detection limit of 0.029 μg l−1, being sensitive enough to be applied to drinking water samples without preconcentration. The immobilized antibody reactor is able to run a whole assay in 20 min, and is reusable for more than 100 of consecutive assay cycles without significant loss of performance. The recognition of l-naphthol — the main metabolite of carbaryl — and other N-methylcarbamate insecticides are also studied, none of these compounds showing cross-reactivity higher than 7%. A preliminary validation of the immunosensor, carried out by analysing real samples spiked with carbaryl, shows good results for bottled water and for commercial honey diluted with PBS (1 gl−1) as the only sample pretreatment.