Development of an impedimetric immunosensor to determine microcystin-LR. New approaches in the use of the electrochemical impedance spectroscopy was used in determining to determine kinetic parameters of immunoreactions

Abstract The development of new electrochemical immunosensors for the detection of environmental contaminants is of great interest due to their simplicity, high sensitivity, and extended analytical range. Because of the antibody is immobilized on the electrode, it is important to determine its loss of reactivity after immobilization. In this work, two aspects were addressed. First, we developed a new methodology based on electrochemical impedance (EI) to determine the kinetic parameters associated with immunoreactions carried out on the electrode. Second, an electrochemical immunosensor based on electrochemical impedance spectroscopy (EIE) was developed to determine microcystin-LR in drinking water samples. Microcystin-LR determination was based on a label-free non-competitive immunoassay. The electrochemical immunosensor shows a limit of detection (LOD) of 33 pg mL−1 (3.32 × 10−11 mol L−1 or 0.033 μg L−1) which is well below the WHO guideline recommendation of 1 μg L−1 and 40 times better than the LOD obtained using the same antibody in an optimized conventional competitive ELISA assay. In addition, an acceptable accuracy, with recovery percentages close to 100% were found. The label-free immunosensor is a valuable tool to monitor microcystin-LR in drinking water samples and the environment.