高效液相色谱-串联质谱法测定葡萄和土壤中噻苯隆残留消解动态

Study on decline and residue of thidiazuron in grape and soil by high performance liquid chromatography-tandem mass spectrometry

【目的】评价噻苯隆在葡萄上的使用安全性。【方法】采用高效液相色谱-串联质谱法建立快速准确的噻苯隆在葡萄及土壤中的残留分析方法,进行2 a两地的消解动态及最终残留试验。【结果】建立的噻苯隆在葡萄及土壤中的残留分析方法表明:噻苯隆在0.01~1.00 mg·L-1内线性关系良好,灵敏度、准确度均符合检测要求。采用该方法研究噻苯隆在葡萄中的消解动态,对葡萄及果园土壤的最终残留进行了测定,结果表明,噻苯隆在葡萄样品中的消解曲线均符合一级动力学方程,半衰期为0.8~5.7 d,最终残留试验表明,在到达安全间隔期14 d时噻苯隆在葡萄中最高残留量为0.020 0mg·kg-1,远低于国家限量标准。【结论】噻苯隆在葡萄中属于易降解农药,降解较快。

[Objective] To understand the dynamic degradation and final residue of thidiazuron in grape fruit and grapery soil, respectively. We propose a high performance liquid chromatography-tandem mass spectrometry （HPLC-MS/MS） method to detect thidiazuron in grape fruit and grapery soil. The degradation of grape in the fruit followed the first order kinetic equation （Cr=C0e^KT）. Therefore, we compute the half-life （T1/2） in the fruit of this plant growth regulators based on that equation. These results will provide guidance on the proper and safe use of this plant growth regulator for grape fruit. [ Methods ] The trials were conducted in experimental fields where located in Henan province and Jiangsu province for past two years. In degradation dynamics experiment, six field plots formed one set, each with two grapevines. 0.1% thidiazuron wettable powder formulations （200 times dilution） were soaked to grape cluster （the half of the mature individuals） and each experiment was conducted in triplicate. The detailed method is described as follows. Firstly, the untreated plots were soaked with water under control. Secondly, the representative samples （grape fruit） were collected at 2 h, 1 d, 2 d, 3 d, 5 d, 7 d, 10 d, 14 d, 21 d and 28 d after thidiazuron treatment. Thirdly, the samples were placed in a freezer with- 20℃ after sample preparation. Fourthly, the pesticide residue in the sample was collected after two hours on the day of applying was set as the original reside, the residue levels in the rest samples were the the degradation rate. Lastly, the dissipation equation was fitted SigmaPlot software. In final residue experiment, according compared with the original residue to get to the first order kinetics equation using to the maximum recommended dose and 1.5 times of the maximum recommended dose, 0.1% thidiazuron wettable powder were soaked to grape cluster 1 or 2 times with an interval of 10 days, grape samples and grapery soil were collected 7, 14 and 21 d after the last treatment. The Pre-treatment methods of thidiazuron residue determination： A 10 g grapery soil or grape fruit was weighed and put into centrifuge tube. A 5 mL ultra pure water and 20 mL acetonitrile was added into grapery soil samples, a 20 mL acetonitrile was added into grape samples. After shaken vigorously by Multi-tube Vortexer for 15 min, 3 g NaCl was added into centrifuge mixture was vortexed for 1 min. The sample solutions were separated by centrifuging with 6 tube and the 000 r·min^-1 for 5 mins, then the supernate filtered with 0.22 μm syring filter for HPLC- MS/MS analysis. [Results]In the concentration range of 0.01-1.0 mg·L^-1, the matrix-matched calibration curves showed good linearity with correlation coefficients 0.999 6. The average recoveries of thidiazuron in the grape and soil were found between 84% and 108% at 0.01-0.50 mg·kg^-1, with relative standard deviations （RSD） of 0.5%- 1.9%. The limit to quantification （LOQ） was 0.01 mg·kg^-1. The efficiency of our proposed method in measuring trace levels of thidiazuron was monitored by analyzing the samples collected from the field trials. In degradation dynamics experiment at Henan and Jiangsu experiment fields, the original residue of thidiazuron in the grape fruit were 0.039 1-0.017 4 mg·kg^-1, the thidiazuron degradation rate found 7 d after treatment were 100%, 100%, 100%, 66.4% in grape fruit for 2014 and 2015. The half-life （T1/2） of thidiazuron in grape fruit from Henan in 2014 and 2015 were 1.7 d and 1.7 d, and from Jiangsu were 0.8 d and 5.7 d. The final residue test showed that thidiazuron was readily degraded in grape and the final residue of thidiazuron in the grapery soil was less than in the grape. In 7, 14 and 21 d after the last pesticide soak, 95.1% of the grapery soil testing data is below LOQ （0.01 mg·kg^-1）, while the grape is 70.1% below LOQ （0.01 mg·kg^-1）, the highest residue in the grape and grapery soil of all final residue test date was 0.024 7 mg·kg^-1 （2014, Jiangsu high-dose group, twice treatment, 7 d）, 0.020 0 mg·kg^-1 （2015, Henan low-dose group, twice treatment; 14 d）, respectively. [Conclusion] The result indicated that thidiazuron is readily degreaded in grape and is safe to environment and soil. In addition, the thidiazuron maximum residue limit （MRL） in grape is 0.05 mg·kg^-1 and the safety period of 0.1% thidiazuron wettable powder is 14 d.