The Application Of Electrochemical Method In The Analysis Of Organophosphorus Pesticide

Organophosphorus and carbamate pesticides have been widely applied for decades in modern agriculture, industry and medicine. Recently, increasing attention has been given these compounds due to the properties of their highly toxic and the accumulation in living organisms. So, the rapid determination and precise quantification of trace level of OP compound are significant to human health and ecological environment. Several analytical techniques such as gas chromatography and liquid chromatography are proposed in order to determine trace levels of these toxic pesticides. Relative to those traditional method, the electrochemical determination as sensitive and selective analytical methods based on the inhibition of acetylcholinesterase has been widespread applied for the detection of the trace level of environment pollutant.This graduation thesis include three sections, as follows:1. The basic property of organophosphorus pesticide and The current situation was described, several traditional determination methods such as gas chromatography and liquid chromatography were also represented. In addition, the electrochemical method based on the inhibition principle of pesticide to the activity of acetylcholinesterase was characterized. In the end, the research target and research mentality of this thesis was also introduced.2. A novel method for the detection of pesticides by inhibition of AChE extracted from earthworm has been developed. Two immiscible phases which the organic phase containing substrate and the aqueous phase containing enzyme are employed. The substrate was hydrolyzed by AChE at the interface of two phases and product spontaneously penetrated into aqueous solution, aroused the transformation of electrochemical signal. Meanwhile, the corresponding relation of the inhibition rate to the concentration of pesticide was displayed in the presence of parathion-methyl. A good linear relationship between pesticide concentration and inhibition rate was obtained in the concentration range of 50ng/ml～10ug/ml.3. In this study, the assay method of AChE based on the formation of water/cyclohexane/lecithin emulsion is evaluated for the detection of organophosphorus pesticides by the inhibition of enzyme. The formation of emulsion not only provide more effective interface between enzyme molecules and substrate due to the substrate molecules are enwrapped into the micelles of lecithin that act as surfactant but also prevent the activity center of AChE contact with oil phase directly and thus avoid the destruction of enzymatic activity. The inhibition efficiency of fenthion with different concentrations versus AChE were evaluated by determining the reduction of peak current due to the catalytic activity of AChE was limited with the addition of pesticide, the pesticide concentrations in the range from lOng/ml to 100μg/ml can be monitored by using this effective inhibition method.