Study On Determination Of Methamidophos And Acephate In Rice By Capillary Electrophoresis

Organophosphorus pesticide is the most widely used pesticide in China. It isuniversally acknowledged that pesticide plays a significant role in promoting thedevelopment of agriculture, forestry and animal husbandry, meeting the demand ofagricultural and sideline products. But the pesticide residue in the environment andbiology not only had serious effect on ecological environment, food safety and humanhealth, but also caused incalculable loss on economic development and internationaltrade, which related to the strategy of the 21st century sustainable development andimprovement of life quality. Therefore, pesticide residue problems are increasinglyaroused the attention of the public. The harm of organophosphorus pesticide is arelative serious problem in China. There is a certain gap between China and foreigncountries in technology, personnel, equipment. The standard method to detectorganophosphorus pesticide residues is gas chromatography (FPD) in China. Itrequires a lot of high-purity hydrogen and the cost is higher. Therefore, it is essentialto revise organophosphorus pesticide residue levels in grain,vegetable and fruit andstudy new detection techniques. One of current issues that needs to be resolved is touse fast, simple, sensitive technology to determine organophosphorus pesticideresidue in crops.At present, the application of capillary electrophoresis method is moreextensive in biochemical analysis. This method is not only effective and fast but alsocheap. This paper investigates the detection of methamidophos and acephate in ricewith capillary electrophoresis. Optimal separation conditions are found throughexperiment: 30mmol/L phosphate buffer solution ( pH=5.9 ) ; quartz capillary : 60cm×50μm (effective length 50cm ) ; gravity injection : height of 10cm, injection time 20s ; operating voltage : 20KV; detection wavelength : 220nm ; room temperature.Methamidophos (4.523min) and acephate (5.001min) is completely separated in 6minin the optimized conditions. There are good linear relationship of the standardworking curve and wide linear range. The detection limit of methamidophos is0.009mg/kg , acephate is 0.005mg/kg ; the precision(RSD)of methamidophos is1.7% , acephate is 2.3% ; the accuracy (recovery) of methamidophos is 82%～91%,acephate is 83%～92%. The method has relatively low detection limit, betterprecision, higher accuracy. It can completely meet the detection requirements ofmethamidophos and acephate in rice.Through the comparison between shaking extraction and ultrasonic extraction,it is known that the best extraction method is to immerse 9min, ultrasound 6min.Ultrasonic extraction saves more time than shaking extraction, and its recovery is alsohigher than shaking extraction. Laboratories commonly have ultrasound device whichcan be applied to deal with samples. Ultrasonic extraction is a low-cost, highefficiency,time-saving method. It is able to achieve good effects in the extraction ofmethamidophos and acephate in rice.Compared with light degradation of methamidophos and acephate in solutionand rice, two conclusions can be listed as follows: 1: Methamidophos and acephate instandard solution produces direct light degradation. Their photolysis half-life are 1.5dand 1d respectively. So standard solution must avoid light and keep it in refrigerate. Itgenerally needs re-preparation after two weeks. 2: Methamidophos and acephate inrice produces direct light degradation. Their photolysis half-life are 1.8d and 1.3drespectively. Methamidophos is a rank poison. Acephate will degrade intomethamidophos, so it should be strictly controlled in usage. Meanwhile the detectionof methamidophos and acephate should be enhanced.