| To establish a national standard method of residue analysis of diflubenzuron in wheat by selection of determination condition and extracting system. Finally, .A method was developed to determine diflubenzuron in wheat. The residue of diflubenzuron in wheat was extracted by acetonitrile , determined by HPLC equipped with UV detector at 254nm. The sensitivity, accuracy, and precision of the method were investigated. The stability of diflubenzuron in acetonitrile, sample extracting solution, matrix, were also studied in the condition of different storage condition. Using the established method, simultaneous analyzed diflubenzuron, flufenoxuron, and iprodione. The main results were summarized as following.1.The HPLC methodThe determination condition of diflubenzuron by HPLC included Hypersil ODS C18 reverse-phase column: 4.6 mm (i.d.)×250mm,mobile phase:acetonitrile∶water(60/40,v/v),velocity of flow:1.0 mL/min,wavelength:λ= 254 nm,column temperature:30℃and injector volume:20μL.The LOQ of this method was 0.04mg·kg-1. The R2 of standard curve of diflubenzuron range from 1 to 400ng was 0.9999.2. The extracted systemExtracting method: The average recoveries from spiked rapeseed extracted by surging and ultrasonic method were respectively 89.37% and 80.60%, the optimal method was surging method.Extracting solvent: The average recoveries from spiked rapeseed extracted by acetone,ethyl acetate,dichloromethane and acetonitrile were respectively 91.27%,72.12%,89.37% and 90.55%,the optimal extracting solvent was acetonitrile. Extracting time: The average recoveries from spiked wheat extracted with surging method by 40,60 and 80min were respectively 68.15%,81.97% and 82.45%, the optimal extracting time was respectively 60min.Extracting times: The average recoveries from spiked wheat extracted by 1, 2 and 3 times were respectively 81.97%,89.37% and 91.26%, the optimal extracting times was 2 times.3. Recovery experiment, sensitivity, accuracy and precision experimentUsing the established method, the average recoveries from spiked wheat with fortified level 0.04mg·kg-1,0.2mg·kg-1 and 1.0mg·kg-1 were 90.25%,89.37%和and 90.87% respectively, the CV were respectively 3.37%,2.37% and 4.15%. The results are all according with the requirement of residual analysis. The minimum detected concentration are 0.04mg·kg-1.4. The matrix-adaptability experimentThe recoveries of diflubenzuron spiked bean and rice were 88.75% and 90.13% , CV were 3.96% and 2.18%, So this method was fit for analyzing diflubenzuron residue in wheat,bean and rice.5. The stability testThe standard solution of diflubenzuron (dissolved in acetonitrile, diluted with acetonitrile) at 1×10-6 g/mL can be stored 3 months at least at 4℃; diflubenzuron in extracted solution of wheat can be stored 30 days at -20℃,4℃a nd 25℃; In the condition of -20℃,4℃and 25℃, decompose rate of diflubenzuron in wheat matrix was 2.18%,3.03% and 4.15% after 60 days. 6. The quality-controlling test. The author put up the quality-controlled to the validity and the precision of the analytical method with the results of that the validity-analysis and the precision-analysis were both in the controlled condition and the analytical data were available.7. Superiority of the established method:There are some superiorities including easy to operate, little analytic time, and goodly recurring. At the same time there are good matrix-adaptability and method-adaptability in this method.
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