Effect of oil adjuvant and starch adjuvant on residues of buprofezin and nitenpyram in rice
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Abstract
In order to investigate the effects of oil adjuvant and starch adjuvant, the residues of buprofezin and nitenpyram were studied using rice as the model plant. A QuEChERS-high performance liquid chromatography-tandem mass spectrometry (HPLC-MS/MS) method was developed to determine their dynamic contents in different parts of rice. Results showed that the recoveries of buprofezin in spike, plant, grain and hull of rice were in the range of 89%-100%, the relative standard deviation (RSD) ranged from 2.5%-7.2% and the quantitative limit (LOQ) ranged from 0.01 to 0.02 mg/kg. The recoveries of nitenpyram in spike, plant, grain and hull of rice were in the range of 88%-99%, the RSD ranged from 2.5%-13% and the quantitative limit (LOQ) ranged from 0.01 to 0.02 mg/kg. The degradation of buprofezin and nitenpyram in different parts of rice was fitted to a first-order reaction kinetic model. In terms of no addition of adjuvant, starch adjuvant, oil adjuvant treatments, the order of the initial deposit residues of buprofezin in spikes of rice were oil adjuvant > starch adjuvant > no adjuvant addition group and that in the half-life were oil adjuvant > starch adjuvant > no adjuvant addition group. In the harvest time of rice, the terminal residues of buprofezin and nitenpyram in grain and hull were undetected. The residue of buprofezin in plant was in the range of < 0.02-0.05 mg/kg and that of nitenpyram was in the range of < 0.02-0.05 mg/kg. The results of field tests of 70% buprofezin + nitenpyram WG against Laodelphax striatellus showed that the control effect of pesticides added with starch adjuvant or oil adjuvant were significantly higher than that with no adjuvant addition 14 days after treatments. The results showed that the adjuvant treatments could extend residue time of the active ingredient of pesticide in rice, which would benefit the lasting of the effect of pesticide. Meanwhile, the terminal residue was low. The effect of oil adjuvant was better than that of the starch adjuvant.
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