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

Abstract

An immunosensor for herbicide simazine has been developed based on the potentiometric detection of the peroxidase label after a competitive immune reaction on the electrode surface. Gold planar electrodes were found to be the most effective supports for immunosensors. Compositions of the substrate solutions 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 regeneration. The limit of simazine detection is 3 ng/ml. The operating lifetime of the sensor is 15 days; 250 tests can be carried out with a signal decreasing not more than 10%. The proposed immunosensor shows 5–6-fold reduction in the analysis time and 25-fold economy of the reactants comparing with the standard microplate ELISA. The two immunoanalytical techniques were applied to detect simazine in meat extracts, milk, tomatoes, cucumbers, and potatoes. For the first three substances, the herbicide was detected quantitatively without pre-treatment. Cucumber and potato matrices caused sorption of endogenous peroxidase, however this effect was eliminated by 5 min boiling. The obtained results confirm the efficiency of the proposed sensor for the food quality control.