Co-isolation of deoxynivalenol and zearalenone with sol-gel immunoaffinity columns for their determination in wheat and wheat products.

The paper describes a sample clean-up method for the co-isolation of deoxynivalenol (DON) and zearalenone (ZON), two mycotoxins naturally co-occurring in wheat. The method is based on immunoaffinity columns prepared by co-immobilising anti-DON and anti-ZON antibodies in a porous sol-gel glass. The main task in developing the method consisted in finding a loading medium allowing retention of both analytes as well as a common elution medium for the dissociation of both antigen-antibody complexes formed. This can be achieved by co-extracting DON and ZON with ACN-water (60:40, v/v), reducing the acetonitril concentration to 2.5% before loading an aliquot of the diluted sample extract onto the DON/ZON column. The columns are washed with 5 ml of MeOH-water (10:90, v/v) before DON and ZON are co-eluted with 4 ml of ACN-water (50:50, v/v). Concentrations of DON and ZON are determined with HPLC-UV and HPLC-fluorescence detection, respectively. The sample clean-up method was shown to be applicable to wheat and wheat products, e.g., cornflakes, milk wheat mash and rusk. Spiking experiments (spike level 500 microg DON/kg and 50 microg ZON/kg) resulted in recovery rates from 82% to 111%.