Studies about the electrochemical determination of zearalenone on a rabbit polyclonal antibody adsorbed on glassy carbon electrodes

P. G. MOLINA; M. A. ZÓN; H. FERNÁNDEZ

Carlos Paz

Congreso; Myco-globe Argentina 2006 ? Conference; 2006

International Society for Mycotoxicology

Zearalenone (ZEA) is an important mycotoxin found in cereals under wet conditions. It is produced by fungi of the genus Fusarium. It has been reported that ingestion of mycotoxins of the Fusarium genus via contamined cereals may lead to fertility disturbances and other reproductive pathologies. Chromatography methods have been the ones most frequently used for determination of ZEA and its derivatives. High performance liquid chromatography seems to be the preferred method when available. Enzyme-linked immunosorbent assays (ELISAs) have been used for the analysis of ZEA in food and feeds. However, these methods have the disadvantage that need greater times in extraction and clean up steps. Besides, the detection is indirect and has some problems due to interfering presence in a complex matrix. In this work, we report preliminary studies for the determination of ZEA by using an electrochemical immunosensor based on a ZEA rabbit polyclonal antibody adsorbed on glassy carbon electrode surfaces in pH 7.40 phosphate buffer solutions by square wave voltammetry. The antibody concentration in the modification solution is varied from 5 to 20 microgramme/milliliter, obtaining an optimal working value of 14.6 microgramme/milliliter. The optimum immersion time of glassy carbon electrodes in the antibody modification solution was 5 min. Besides, the ZEA adsorption time on both the bare and antibody modified electrodes was also analysed. An optimal value of 60 s was found for these purposes. Results obtained with modified electrodes are compared with those on the bare electrode. The ZEA adsorption isotherm on the antibody modified electrodes was derived from the dependence between the fractional coverage of the electrode surface and ZEA bulk concentration (c*ZEA). The saturation coverage of the electrode surface was reached at a c*ZEA greater than 1.5 x 10-5 M. Experimental results were then fitted in order to find the best adsorption isotherm to describe the specific interaction of ZEA with both the bare and the antibody modified electrodes. The best fitting was achieved when the Freundlich adsorption isotherm was chosen to perform the fit. From calibration curves generated by square wave voltammetry a detection limit of 2 x 10-7 M was determined for a signal to noise ratio of 3:1. These preliminary studies were carried out by employing the ZEA commercial reagent. However, additional studies have been undertaken in our laboratory to study the application of this electroanalytical methodology for the determination of ZEA in real samples.