Comparative Study of Pesticides Analysis Using Enzyme Inhibition Sensor and Gas Chromatography Methods

Pesticides are widely used in paddy field to control pests, diseases, weeds and other rice pathogens in minimizing a serious loss in rice production. The presence of pesticide residues and metabolites in rice, water, soil, currently represents a major environmental pollutant issues. It sometime will cause insect pest outbreaks in paddy field. An electrochemical enzyme inhibition sensor using screen-printed carbon working electrode with onboard carbon counter and silver-silver chloride pseudo-reference electrode for insecticides detection is described in this paper (Figure 1). The detection is based on the inhibition of insecticides used in paddy field towards acetyl-cholinesterase enzyme (AChE) with the presence of Acetylthiocholine Iodide (ATCh) substrate on the sensor surface. The mixtures of AChE enzyme (0.02 UmL-1), electron mediator, TCNQ (1mM) and polypyrrole matrix (75 mM) were electro- polymerized on the sensor surface with a constant potential of 1.0V for 20 minutes. The sensor was soaked for 5 minutes with insecticides standard or sample containing insecticides before the electrochemical measurement was taken by adding Acetylthiocholine Iodide substrate in KCl (0.08M, pH 7.5) which acts as the enzyme mediator /substrate system. The current measurement was conducted using chronoamperometry at 100mV vs. on board screen-printed Ag-AgCl pseudo- reference electrode. Comparative analysis of spiked water samples with 0.1ppm pesticides and real samples (paddy) also were conducted using enzyme inhibition sensor and gas chromatography methods. From the data analysis, it showed very comparable results with R2 = 0.96 in the correlation plot for paddy samples samples. This makes the developed sensor a potential tool for the rapid, simple and sensitive detection of insecticides residues in agriculture industry.