Enzymatic Determination of Organo-Phosphorus Pesticides with a Surface Acoustic Wave Impedance Sensor

A novel and sensitive method, based on the inhibition of the lipase-catalyzed hydrolysis by combining hydroxyle groups of lipase with organophosphorous pesticide, is proposed for the enzymatic determination of organophosphorous pesticide. The inhibited enzymatic reaction is monitored with an SAW/impedance enzyme transducer, which is composed of an SAW resonator, oscillating at 61 MHz, and a pair of parallel electrodes. Employing the method described, the frequency response of the transducer is proportional to organophosphorus pesticide concentration over the range of 227ng/mL - 2.27μg/mL; the detection limit is 76ng/mL. The effects of temperature, pH, incubation, and solvent are also investigated. The method was successfully applied to the determination of dichlovors residues in the root, stem, and blade of Chinese cabbage.