Development Of The National Standard Method For Residue Analysis Of Cyhalothrin In Wheat

This dissertation was concerning with studies on the national standard method of residue analysis of cyhalothrin in wheat by selection of determination condition, extracting system and clean-up system. Finally, it was optimized and combined to determine the residue of cyhalothrin in wheat with Gas Chromatography (GC). The sensitivity, accuracy, and precision of the method were investigated. And the stability of cyhalothrin in standard solution, sample extracting solution and stocked sample were also studied. The residue of cyhalothrin in rice,corn, were investigated. The main results were summarized as following:1.The determination condition of cyhalothrin by GC as follows ,detector temperature was 320℃, injector temperature was 260℃,column program: 60℃for 1min;60℃to 180℃at 25℃/min, 180℃to 200℃at 5℃/min,200℃to 260℃at 15℃/min, for 7min.Carrier gas was Nitrogen at 3 mL/min, and injector volume:2μL.2. The studies on extracting system of wheat indicated that: the recovery was highest extracted with petrolem ether, and was 83.39%. The target and impurity were completely separated in chromatogram. The average recoveries from spiked wheat extracted by surging and ultrasonic method were all beyond 80%, and there was also no marked difference in the level of 0.05, so the optimal method was easy to operated surging. The optimal extracting time and extracting solvent dosage were respectively 60min and 80mL by compared.3. The studies on purified system of wheat indicated that: The average recoveries from spiked wheat purified with. The experiment on column chromatography indicated that : the sorbent is 4g 5%(hydrous volume)neutral Al2O3 and 0.01g active carbon , pre-eluted by petroleum ether 20mL, eluant is petroleum ether / ethyl acetate (95∶5,V/V)50mL, collect the eluant.4. Recovery experiment, sensitivity, accuracy and precision experiment showed that wheat samples were fortified with cyhalothrin at levels between 0.05 and 1.0mg/kg, the recoveries were respectively in the range of 83.22%～84.60%, the CV were respectively 1.80%～4.60%. The minimum detected concentration are respectively 0.005mg/kg.5. The researches on stability indicated that cyhalothrin in standard working solutions, extraction of matrix and matrix is stable stored in -20℃, 4℃and room temperature. Standard working solutions at least were stored 50d at 4℃. The extraction of wheat at least were stored 7d at different conditions. cyhalothrin in wheat may be stored 21d at different temperature.6. The matrix-adaptability test indicated that using the established method, the recoveries of cyhalothrin in fortified rice,corn, at level of 0.2mg/kg were respectively 88.99%,89.76%, CV were between 0.71% and 3.60%. The result met the need of the pesticide residue analysis. So the established method was fit for analysing cyhalothrin in rice, corn.7. Superiority of the established method: there are some superiorities including easy to operate, low analytic cost, friendly environment and goodly recurring. At the same time there is good matrix-adaptability in this method.