Development of a potentiometric immunosensor for herbicide simazine and its application for food testing

An immunosensor for herbicide simazine has been developed based on the pote ntiometric detection of the peroxidase label after a competitive immune rea ction on the electrode surface. Gold planar electrodes were found to be the most effective supports for immunosensors. Compositions of the substrate s olutions were optimized for potentiometric measurements. A total of 50% of immobilized antibodies are saturated by the labeled simazine within 2 min, and 65% within 5 min. Total assay time is 14 min including the electrode re generation. The limit of simazine detection is 3 ng/ml. The operating lifet ime of the sensor is 15 days; 250 tests can be carried out with a signal de creasing not more than 10%. The proposed immunosensor shows 5-6-fold reduct ion in the analysis time and 25-fold economy of the reactants comparing wit h the standard microplate ELISA. The two immunoanalytical techniques were a pplied to detect simazine in meat extracts, milk, tomatoes, cucumbers, and potatoes. For the first three substances, the herbicide was detected quanti tatively without pretreatment. Cucumber and potato matrices caused sorption of endogenous peroxidase, however this effect was eliminated by 5 min boil ing. The obtained results confirm the efficiency of the proposed sensor for the food quality control. (C) 2001 Published by Elsevier Science B.V.