Development of a very sensitive electrochemical magneto immunosensor for the direct determination of ochratoxin A in red wine

An electrochemical immunosensor (EI) for the determination of ochratoxin A (OTA) in red wine samples was developed. This immunosensor was based on Protein G functionalized magnetic beads (MBs) as solid phase for affinity reaction between OTA and OTA monoclonal antibody (mAbOTA). A carbon screen printed-electrodes (CSPE) system was used as electrochemical transduction element. This immunosensor was based on a direct competitive assay between OTA in wine samples and OTA labeled with horseradish peroxidase (HRP) (OTA–HRP). The HRP, in the presence of hydrogen peroxide catalyzes the oxidation of pyrocatechol to benzoquinone, whose back electrochemical reduction was detected on a CSPE by square wave voltammetry (SWV). The experimental variables involved in the immunosensor response to OTA were evaluated. The performance obtained for the EI was an analytical range of 0.01–20 ppb, limit of detection (LOD) of 0.008 ppb, and IC50 = 0.272 ± 0.081 ppb. In addition, an acceptable accuracy with a relative standard deviation (RSD) of 5.56% and very good recoveries (92–110%) were found. This work shows the potential of our EI for the direct measurement of OTA in red wine samples combining SWV as electroanalytical technique with the MBs and CSPE. This EI has great advantages as direct measurement of red wine samples without a prior pretreatment, the small volume of sample, the short time consuming of experiences and LOD well below those established by the Regulatory Commission of the European Community (2 μg kg−1).