Residual Analysis And Digestion Dynamic Study Of 0.2% Thidiazuronco Solution On Tobacco

A simple,rapid and sensitive liquid chromatography–tandem mass spectrometry(LC–MS/MS)method was developed for the determination of thidiazuron(TDZ),in soil,fresh tobacco leaf,and cured tobacco leaf.The field experiments were carried from June to July at Guizhou,Hunan,Shandong,Heilongjiang,Guangxi and.Yunnan.At the same time,the migration of TDZ in tobacco plants and the effect of soil properties on the digestion of TDZ were also explored indoors.It is reasonable to apply the method and collection interval of TDZ on tobacco,and TDZ can be transferred up or down in tobacco plants.Firstly,the pretreatment method for the TDZ in each matrix was optimized,and the pretreatment method of TDZ in each matrix was determined.in this method,TDZ has a good linear relationship between 0.0005–0.1?g/mL,and the linear correlation coefficient(R~2)is 0.9968–0.9994.The detection limits of TDZ ranged from 0.03?g/kg to 0.15?g/kg,and the limits of quantification ranged from 0.1–0.5?g/kg.The average recoveries of TDZ in soil,tobacco leaf(fresh,cured),stem,and root were between 75.39%and 98.51%with intra–day relative standard deviations(RSDs)between 1.06%and 4.91%and inter–day RSDs between 1.49%and 7.52%.The results show that the accuracy,sensitivity and precision of the method are require for pesticide residue analysis and can be used for the detection of actual samples.Secondly,the valid method was used to determine the amount of TDZ residues in tobacco and soil samples under open field and laboratory conditions.Field experiments were carried out in six agricultural sites of China,and the results showed that the half–lives of TDZ were 4.81–9.12 days and 1.42–4.95 days in soil and fresh tobacco leaves,respectively.The terminal concentration of TDZ in cured tobacco leaves were<0.5–7.46?g/kg,and in soil were<0.1–0.5?g/kg.The results show that the application method and harvesting interval are reasonable.Then,for foliar spary and rooting treatment,the concentration of TDZ in root and stem peaked at 5 d,and peaked in soil and tobacco leaf at 7 d;The transfer factor(TF)of the root irrigation was approximately ten times of TF of the foliage spray.The results show that TDZ can be transferred upward and downward in tobacco plants.Finally,the cold storage stability of TDZ in cured tobacco leaf in 360 d at–20°C and an indoor soil degradation experiment were conducted under laboratory conditions.Furthermore,the influence of organic matter in soil on the degradation of TDZ was discussed.The results indicated that the degradation rate of TDZ at–20°C on cured tobacco leaves were lower than 21.35%in 360 d.And soil organic matter can speed up the degradation of TDZ in soil.