Studies On The Residues Of Bromoxynil And Mesotrione In Maize And Soil

The simple, rapid and reliable analytical methods of bromoxynil and mesotrione residues in maize and soil have been established in this study by high performance liquid chromatograpy tandem mass spectrometry (HPLC-MS/MS), respectively. At the same time, the ultimate residue and dissipation of bromoxynil and mesotrione in maize and soil under the field ecosystem have been also investigated, respectively.The analytical method of bromoxynil: The soil and maize samples were shaken and extracted with acetonitrile, and then the soil and maize grain were cleaned up with primary secondary amine (PSA), the maize plant and maize stem were cleaned up with PSA and graphitized carbon black (GCB). The bromoxynil residues were analyzed by high performance liquid chromatography tandem mass spectrometry (HPLC-MS/MS).The fortified recoveries of the method in soil were from 76.28% to 100.12% with relative standard deviations (RSD) from 1.91% to 5.33%; in maize plant were from 73.15% to 93.25% with RSD from 3.26% to 5.08%; in maize grain were from 75.60% to 109.26%, with RSD from 4.00% to 8.87%; in maize stem were from 75.20% to 85.39% with RSD from 6.35% to 8.39%. The limit of quantification (LOQ) was 0.01, 0.02, 0.01 and 0.05 mg/kg for soil, maize plant, maize grain and maize stem, respectively.The analytical method of mesotrione: The soil samples were shaken and ultrasonic extracted with methanol-water solution (50:50, V/V), and the mesotrione residues in soil were analyzed by HPLC-MS/MS. The fortified recoveries of the method in soil were from 83.30% to 91.38% with RSD from 0.07% to 11.80%. The maize samples were shaken and extracted with acetonitrile-water solution (50:50, V/V), and then the maize grain were cleaned up with PSA, the maize plant and maize stem were cleaned up with PSA and GCB. The mesotrione residues were analyzed by HPLC-MS/MS. The fortified recoveries of the method in maize plant were from 78.49% to 82.29% with RSD from 2.58% to 11.95%; in maize grain were from 68.95% to 103.59%, with RSD from 1.58% to 12.05%; in maize stem were from 80.89% to 94.42% with RSD from 6.96% to 11.89%. The limit of quantification (LOQ) was 0.02, 0.01, 0.005 and 0.05 mg/kg for soil, maize plant, maize grain and maize stem, respectively.The maize field trials of bromoxynil and mesotrione were carried out in Beijing and Shandong province in 2009 and 2010. The results of the degradation dynamic trials on maize field suggested that both bromoxynil and mesotrione dissipated in soil and maize coincided with the equation Ct=C0e-kt. The half-lives of bromoxynil in 2009 and 2010 were 9.90 and 4.11 days (Beijing soil); 3.87 and 2.29 days (Shandong soil); 0.81 and 2.55 days (Beijing maize plant); 2.20 and 0.72 days (Shandong maize plant), respectively. In the ultimate experiments, according to the usage guide of the formulation of bromoxynil, the maize plants were sprayed once with the high recommended dosage and 1.5 times of the recommended dosage when the maize plants were at 3~5 leaf stage or the weed was at 2~5 leaf stage. At the time of the harvest, maize grain, stem, and soil was sampled. The ultimate residues of bromoxynil were undetectable in soil, maize grain and maize stem.The half-lives of mesotrione in 2009 and 2010 were 8.90 and 1.02 days (Beijing soil); 1.80 and 5.65 days (Shandong soil); 1.37 and 1.43 days (Beijing maize plant); 0.97 and 0.39 days (Shandong maize plant), respectively. In the ultimate experiments, according to the usage guide of the formulation of mesotrione, the maize plants were sprayed once with the high recommended dosage and 1.5 times of the recommended dosage when the maize plants were at 5~6 leaf stage. At the time of the harvest, maize grain, stem, and soil was sampled. The ultimate residues of mesotrione were undetectable in soil, maize grain and maize stem.The results showed that the simple, specific and sensitive residue analytical methods of bromoxynil and mesotrione were established. The dissipation of bromoxynil and mesotrione were both quick in soil and maize plants. The ultimate residues were undetectable in the soil, maize grain and maize stem. It was safe for the bromoxynil and mesotrione were used with the recommended dosage under the maize open field...