This paper presents the characterization and optimization of biosensors based on graphite-epoxy which incorporates the\nenzyme acetylcholinesterase (AChE). By means of advanced electrochemical techniques, such as electrochemical impedance\nspectroscopy (EIS) and cyclic voltammetry (CV), the characterization and optimization of graphite-epoxy-AChE biosensors\nhave been performed. In order to obtain sensitive electrodes, the optimal composition of the transducer material (graphiteepoxy-\nenzyme ratio) was studied.The optimization of the conductive particles distribution inside the biomaterial has allowed an\nimprovement of the electrochemical properties. Optimal composition guarantees improving electrochemical properties required,\nsuch as high electron-transfer rate, high signal-to-noise ratio, and suitable sensitivity. The optimal biocomposite composition\nrange was obtained between 16% and 17% of graphite and 0.12% of AChE. The biosensors were applied to the analysis of\ndifferent pesticides, organophosphorus and carbamates, using indirectmeasurements based on enzymatic inhibition process. These\noptimized biosensors present detection limit one order of magnitude lower compared to the standard composition (nonoptimized)\nand allow achieving concentrations lower than the established ones by the pesticides regulation. Finally, spiked tap water samples\nwith pesticides were analyzed with the optimized biosensors
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