Studies On Analytical Methods And Dynamics Of Tribenuron-methyl And Fluroxypyr Residues In Wheat And Soil

The analytical methods and dynamics of tribenuron-methyl and fluroxypyr residues in wheat and soil were studied in this dissertation. The sensitivity, accuracy and precision of the methods were investigated. The study provides theoretical reference for using tribenuron-methyl and fluroxypyr properly in wheat field. The main results were summarized as following:1. The analytical methods for tribenuron-methyl residues in wheat plant, wheat seed and soilSoil samples were extracted by mechanical oscillation with mixture of phosphate- buffer and methanol for 2 times, and cleaned up with SPE column; wheat samples extract in methanol, petroleum by liquid-liquid and purification using SPE column; wheat grain samples extracte using dichloromethane. Tribenuron-methyl in samples was determinated by HPLC with UV detector.Determination conditions: Agilent 1200 high performance liquid chromatography equipped with UV, Column: 250mm×4.6mm Agilent ZORBAX-ODS, detector wavelength: 240nm, mobile phases: acetonitrile and 0.5% acetic acid (45:55, v/v), flow velocity: 1mL/min, Oven temperature: 30℃. The retention time of tribenuron-methyl was about 10.4min. The limit of instrumental detection was1.0×10-9 g. Extraction system: Comparing the residue analysis results of tribenuron-methyl with mechanical oscillation and ultrasonic oscillation, we selected mechanical oscillation for 30minutes + 15minutes as the optimized extract method; Comparing the residue analysis results of tribenuron-methyl with dichloromethane,methanol,acetonitrile and 0.2 mol / L phosphate-buffer and methanol (8:2, v / v), we selected methanol ,dichloromethane and0.2 mol / L phosphate-buffer and methanol as the optimized extract solvent respectively in wheat plant,seed and soil.Clean-up system: Identifing SPE column to Clean up in soil ,comparing the purifying effect of elue of the ratio of 1 / 9, 2 / 8, 3 / 7, 1 / 1 (v / v) acetonitrile and pH7.8- 0.2mol / L phosphate-buffer in four of and the recovery rate of Collection of different amounts of acetonitrile and pH7.8 -0.2mol / L phosphate-buffer (1 / 1, v / v), we selected 4mL acetonitrile and pH7.8- 0.2mol / L phosphate-buffer as the optimized elute solvent and collected 3mL acetonitrile and pH7.8 -0.2mol / L phosphate-buffer (1 / 1, v / v). Clean-up of wheat plant on the basis of soil firstly use of 40mL, 30mL petroleum ether to extract and clean up, except for a large number of pigment.The experiments of fortified samples: Four different concentrations of 0.01mg/kg,0.04 mg/kg,0.40mg/kg,0.80mg/kg were fortified respectively in wheat plant and soil,and 0.025mg/kg,0.04mg/kg,0.40mg/kg,0.80mg/kg were fortified in wheat seed. The recoveries of tribenuron-methyl in wheat plant were ranged between 73.1～85.3% , and the CV ranged between 5.88%～8.53%. The recoveries and the CV in soil were ranged between 80.1%～95.2%and 3.41%~7.90%. The recoveries and the CV in seed were ranged between 73.3%~87.5% and 3.21 %~6.49%. This results showed that the method accorded with demands of pesticide residue analysis.2.The analytical methods for fluroxypyr in wheat plant,wheat seed and soil Samples was estracted by mechanical oscillation with alkaline methanol, and cleaned up by liquid-liquid method ,with concentrated sulfuric acid as a catalyst and methanol as the derivatization reagent, after the reaction, the petroleum extracted fluroxypyr .Fluroxypyr in samples was determinated by GC with ECD detector. Determination conditions: Agilent 6890 Gas Chromatography equipped with ECD, Column: 30.0m×250um×0.25um Capillary column, detector temperature was 300℃,injector temperature was 250℃,column program: 70℃for 1min;70℃to 240℃at 20℃/min,240℃for 6min.Carrier gas was Nitrogen at 1 mL/min. The retention time of fluroxypyr was about10.5 min min.The limit of instrumental detection was1.0×10-11 g. Extraction system: Comparing the residue analysis results of fluroxypyr with mechanical oscillation and ultrasonic oscillation, we selected mechanical oscillation for 30 minutes as the optimized extract method. Comparing the residue analysis results of fluroxypyr by different extract solvents of acetonitrile, ethyl acetate and alkaline methanol we selected alkaline methanol as the optimized extract solvent.Clean-up system: Comparing liquid-liquid extraction and solid-phase extraction method , we selected liquid-liquid extraction to clean up. In the alkaline methanol , fluroxypyr salt and dissolve in water, some organic substance retained in organic solvents to abandon in order to achieve the purpose of purification.The experiments of fortified samples: Four different concentrations of 0.01mg/kg,0.04mg/kg,0.40mg/kg,0.80mg/kg were fortified respectively in wheat plant,seed and soil. The recoveries of fluroxypyr in wheat plant were ranged between 72.3%~86.7% , and the CV ranged between 3.02%~8.59%. The recoveries and the CV in seed were ranged between 77.7%~87.3% and 2.75%~7.61%. The recoveries and the CV in soil were ranged between 83.6%~95.8% and 2.87%~8.46%. This results showed that the method accorded with demands of pesticide residue analysis.3.Dynamics of tribenuron-methyl residues in wheat plant and soilThe degradation of tribenuron-methyl in wheat and soil were studied in Hefei and Qingdao. The degradation procedure of tribenuron-methyl and fluroxypyr was correspond to the mathematic pattern. In the wheat plant, the dynamic equation in Hefei was C=0.0593e-0.1393t and half-life was 4.97 d, and the dynamic equation in Qingdao was C= 0.0826e-0.1659t and half-life was 4.18d. In soil, the dynamic equation in Hefei was C= 0.0434e-0.1250t and half-life was 5.54d,and the dynamic equation in Qingdao was C= 0.0572e-0.1306t and half-life was 5.31d. All the final sample was not detected with tribenuron-methyl in Hefei and Qingdao.4.Dynamics of fluroxypyr residues in wheat plant and soilThe degradation of fluroxypyr in wheat and soil were studied in Hefei and Qingdao. The degradation procedure of tribenuron-methyl and fluroxypyr was correspond to the mathematic pattern. In the wheat plant, the dynamic equation in Hefei was C= 0.1226e-0.1171t and half-life was 5.92 d, and the dynamic equation in Qingdao was C= 0.2149e-0.1368t and half-life was 5.07d. In soil, the dynamic equation in Hefei was C= 0.0861e-0.0828t and half-life was 8.37d,and the dynamic equation in Qingdao was C= 0.1478e-0.0893t and half-life was 7.76d. All the final sample was not detected with fluroxypyr in Hefei and Qingdao.