棉籽中单氰胺储藏稳定性及残留行为

Storage stability and residue behavior of cyanamide in cotton seed

中文关键词:  单氰胺  液相色谱-串联质谱法  棉籽  储藏稳定性  残留  消解

英文关键词:cyanamide  liquid chromatography-tandem mass spectrometry  cotton seed  storage stability  residue  dissipation

中文摘要:

      目的 建立测定棉籽中单氰胺残留的液相色谱-串联质谱法(liquid chromatography-tandem mass spectrometry, LC-MS/MS), 研究棉籽中单氰胺的储藏稳定性和大田施药后单氰胺在棉籽中的残留行为及其消解规律。方法 样品用乙腈-水溶液(80:20, V:V)提取, 离心后用丹磺酰氯进行衍生化反应, 离心、过膜, 滤液用液相色谱-串联质谱法检测, 外标法定量。用所建立的检测方法对储藏试验样品和残留试验样品进行测定和分析。结果 在0.01、0.04、0.40、4.00、50.00 mg/kg 5个添加水平下, 棉籽样品中单氰胺的平均回收率为75.7%~91.4%, 相对标准偏差(n=5)为2.0%~5.5%, 定量限为0.010 mg/kg。储藏稳定性试验结果表明: 棉籽样品在低于?18 ℃条件下储藏56 d, 单氰胺降解率小于30%。残留试验结果表明: 20%单氰胺水剂按照用药量20倍液(有效成分浓度: 10 g/kg)施药1次, 采收间隔期15、25 d, 收获的棉籽中单氰胺残留量为<0.010~0.018 mg/kg; 单氰胺在棉籽中的消解半衰期为2.6~5.1 d。结论 该检测方法准确、灵敏且简便、快速, 满足农药残留检测要求; 不高于-18 ℃储藏条件下, 单氰胺在棉籽中的储藏稳定期为56 d; 依据单氰胺在棉籽中的残留行为, 本研究提出了20%单氰胺水剂作为脱叶剂在棉花上的合理使用建议。

英文摘要:

      Objective To establish an analytical method for the determination of cyanamide residue in cotton seed by liquid chromatography-tandem mass spectrometry (LC-MS/MS), evaluate cyanamide storage stability, and investigate cyanamide residue behavior and its dissipation in cotton seed after field application. Methods Cotton seed samples were extracted with acetonitrile-water solution (80:20, V:V), the divided extract was derivatized with dansyl chloride after centrifugation, and then the derivatized sample extracts were centrifuged and filtered, the analyte was analyzed by liquid chromatography-tandem mass spectrometry and quantified with the external standard method. Stored analytical samples and field samples were determined by the established method. Results The average recoveries of cyanamide in cotton seed ranged from 75.7% to 91.4% at 5 spiked levels of 0.01, 0.04, 0.40, 4.00 and 50.00 mg/kg, with relative standard deviations (n=5) between 2.0% and 5.5%, the limit of quantification was 0.010 mg/kg. The storage stability test results showed that the degradation rate of cyanamide in cotton seed samples stored at ?18 ℃ for 56 d was less than 30%. Residue test results showed that the cyanamide residues were <0.010?0.018 mg/kg in harvested cotton seed after 15 and 25 d from applying 20% cyanamide aqueous solution once according to the dosage of dilution mutilple of 20 times (active ingredient concentration: 10 g/kg); and the dissipation half-life of cyanamide in cotton seed was 2.6-5.1 d. Conclusion This method is accurate, sensitive, simple and rapid, which can meet the requirements of pesticide residue determination; under the condition of no more than ?18 ℃, the storage stability period of cyanamide in cotton seed is 56 d; the reasonable use of 20% cyanamide as defoliating agent in cotton is suggested based on the residual behavior of cyanamide in cotton seeds.