The Dynamics Of Residues Analysis Of Pymetrozine And Spinosad On Tobacco

In this dissertation, the main of the work is to develop a new simple and reliable method for analysis of pymetrozine residues in green tobacco leaves using solid-phase extraction. Meanwhile, we investigated the residual dynamics of pymetrozine in green tobacco leaves through field experiment. The second work is to develop a new method for analysis of spinosad residues in warehouse tobacco. At the same time, our main studied the duration of pest control in warehouse tobacco. The summarizations of it are follows:In order to optimize the pretreatment conditions, we researched the purifying effect of the three SPE columns (Sep-Pak Florisil, Sep-Pak silica gel and Pesticarb/NH2). An analytical method has been developed to determine pymetrozine residues in flue-cured tobacco, using solid phase extraction (SPE) and high-performance liquid chromatography (HPLC). The analytical procedure involved in ultrasonic extraction with acetonitrile, purification using a Pesticarb/NH2 SPE column and acetonitrile/toluene (3:1, v/v) as eluent. The eluate was blown to dryness under a stream of nitrogen and the residue was dissolved in 1mL of the mobile phase, and analyzed by HPLC. The method is simplicity, accurate, rapid, sensitive and reproducible for determining the pymetrozine residues in tobacco leaves.The pymetrozine residues levels in green tobacco leaves were evaluated by extracting using acetonitrile-water, clean-up using two SPE cartridges (a Chem Elut SPE cartridge and a PestiCarb/NH2 SPE cartridge) and analyzing by HPLC-UV. Average recoveries ranged from 97% to 99%, with SDs below 2.1%. The limit of detection (LOD) was 0.0050μg/mL. In field trial, pymetrozine was treated with spraying and irrigation respectively. Data indicated that higher residues of pymetrozine were found in 1 to 2 weeks after used the pesticide. After 4 weeks, the residues were lower than the guidance residue limit (GRLs, 1.00 mg/kg) established by the COREST.A new method for analysis of spinosad residues in warehouse tobacco has been developed. Tobacco samples pretreatment combination with liquid-liquid extraction and solid-phase extraction, through optimize the pretreatment conditions, spinosad and other impurities can be separated. Spinosad concentration of 5 and 10 mg/kg of tobacco samples placed after 3, 12 and 18 months; we investigated the concentration changes of spinosad using the established analytical method. The experimental results show that: spinosad concentration of 5 and 10 mg/kg of tobacco samples placed 3, 12 and 18 months later, its little change in concentration of spinosad. The results of samples smoking showe that: tobacco contains spinosad residues has little effect on the quality somking, so spinosad for pest prevention and control of tobacco warehouse have practical significane.