Single and multi-analyte surface plasmon resonance assays for simultaneous detection of cholinesterase inhibiting pesticides

On-line determination of pollutants within the two main types of cholinesterase inhibitors: organophosphate pesticide chlorpyrifos and carbaryl, a carbamate insecticide, is carried out by a new developed surface plasmon resonance (SPR) optical immunosensor. Two different immunoassay approaches have been tested to detect the target analytes by using individual and simultaneous immobilization formats. The formation of an alkanethiol self-assembled monolayer (SAM) allows the repeated use of the same sensor surface. The regeneration of the immunosurface is accomplished throughout approximately 200 assay cycles without degradation of the covalently immobilized molecule. Sensor surface reusability is also evaluated by assessing the SPR signal deviation from the initial value at the beginning of the analysis. Detection limits reached ppt levels (52 and 58 ng L−1) when using chlorpyrifos both individual and multi-analyte protocols. For carbaryl single and simultaneous immunoassay formats, limits of detection were obtained within the 1.41–0.47 μg L−1 range. The immunosensor response comprised 20 min for a complete assay cycle. The SPR-sensor system developed is already commercialised by the company SENSIA, S.L.