Abstract: An electrochemical biosensor for determination of herbicide was prepared. It was based on the antagonism of herbicides on the decomposition of hydrogen peroxide catalyzed by the thykaloid-bound enzymes. The thylakoid membrane isolated from spinach leaves was immobilized by entrapment in polyvinylalcohol bearing styrylpyridinium groups(PVA-SbQ). The thylakoid membrane was fixed on the head of a platinum electrode. Oxidative current of hydrogen peroxide was detected by differential pulse voltammetry in Tris-HCl buffer solution(pH=7.4) containing 1×10^-3 mol/L NaCl, 5×10^-3 mol/L MgCl₂ and 0.01 mol/L hydrogen peroxides. Some herbicides have been detected in the concentration ranges of 3×10^-9-1.5×10^-7 mol/L for paraquat, 1×10^-8-3×10^-7 mol/L for diuron, 4×10^-8-3×10^-6 mol/L for prometryn, 1×10^-7- 5×10^-6 mol/L for atrazine and 1×10^-7- 5×10^-6 mol/L for ametryn, respectively. The method for immobilizing thylakoid in PVA-SbQ membrane was found to be promising to make enzymes stable for several months. The mechanism for this antagonism on the enzymatic decomposition of hydrogen peroxide has been discussed.

Key words: Thylakoid, Antagonism, Herbicide, Biosensor, Differential pulse voltammetry