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建立了丁虫腈在土壤、玉米植株及玉米籽粒中残留的气相色谱分析方法。玉米植株和籽粒样品用乙腈提取,经Oasis HLB固相萃取柱净化;土壤样品用丙酮提取,经液-液萃取净化,气相色谱-电子捕获检测器(GC-ECD)检测,外标法定量。结果表明:在0.01、0.05和0.5 mg/kg 3个添加水平下,丁虫腈的回收率为80%~86%,相对标准偏差(RSD)为5.1%~8.0%;其在土壤、玉米植株及籽粒中的定量限(LOQ)均为0.01 mg/kg。采用所建立的方法对丁虫腈在玉米和土壤中的残留及消解动态进行研究的结果表明:丁虫腈在土壤和玉米植株中的半衰期分别为6.77和2.44 d。采用5%的丁虫腈乳油按推荐高剂量(有效成分)37.5 g/hm2及其1.5倍该剂量(56.25 g/hm2)于玉米苗后茎叶初期施药1次,在玉米乳熟期和成熟期时,玉米籽粒中丁虫腈的最终残留量均低于定量限;玉米收获时(距施药90 d),籽粒中丁虫腈的残留量均低于参考的MRL值(0.02 mg/kg,氟虫腈在谷物中的最大残留限量)。
A gas chromatographic method was established for the determination of stilbene residues in soil, corn plants and maize seeds. Corn plants and grain samples were extracted with acetonitrile and purified by Oasis HLB SPE. Soil samples were extracted with acetone, purified by liquid-liquid extraction, detected by gas chromatography-electron capture detector (GC-ECD) and quantified by external standard method. The results showed that the recoveries of stilbene were between 80% and 86% and the relative standard deviations (RSDs) were between 5.1% and 8.0% at the three levels of 0.01, 0.05 and 0.5 mg / kg, respectively. And the limit of quantitation (LOQ) in the grain were both 0.01 mg / kg. The results showed that the half-lives of siphonon in soil and maize plants were 6.77 and 2.44 d, respectively. 5% of the insecticide EC was applied at the initial high dosage (active ingredient) 37.5 g / hm2 and its 1.5 times (56.25 g / hm2) At maturity, the final residues of scriproses in maize kernels were lower than the limit of quantification. The residues of stilbene in kernels were lower than the reference MRL (0.02 mg / kg, maximum residue limit of fipronil in grains).