Sensitive enzyme-biosensor based on screen-printed electrodes for Ochratoxin A

Horseradish peroxidase has been successfully immobilized in a polypyrrole matrix onto disposable screen-printed carbon electrodes for the selective detection of Ochratoxin A. The chronoamperometric determination of this mycotoxin has been optimized by experimental design methodology, which implied the join evaluation of pH of the buffer solution, applied potential and concentration of H2O2. The slopes of the calibration curves built under the optimum conditions of the experimental variables have been used to estimate the reproducibility and the repeatability of the developed biosensor for Ochratoxin A. Relative standard deviation values of 1.9% (n = 5 and alpha = 0.05) and 7.1% (n = 4 and alpha = 0.05) were obtained for reproducibility and repeatability, respectively. The capability of detection for this method was 0.1 ng mL(-1) (alpha = 0.05 and beta < 0.05). The viability of the developed biosensor in the determination of Ochratoxin A in spiked beer and in roasted coffee has been shown, yielding average recoveries of 103% and 99%, in that order, with relative standard deviation values less than 5% (n = 3 and alpha = 0.05) in both cases. (C) 2009 Elsevier B.V. All rights reserved.