Study On The Residue Dynamics And Removal Technology Of Imidacloprid And Fenpyroximate In Celery

In this study,a simple and practical Ultra-high performance liquid chromatography-tandem mass spectrometry method was established to detect the residues of imidacloprid and fenpyroximate in the roots,stems,leaves and plants of celery.The residue dynamics studies of imidacloprid and fenpyroximate in roots,stems,leaves,plant of celery were sprayed with imidacloprid and fenpyroximate.And the changes of physiological and biochemical indexes in the plants of celery were carried out by spraying with imidacloprid and fenpyroximate.In addition,the effects of different washing methods on the removal of imidacloprid and fenpyroximate in the plants of celery were studied.The main conclusions are as follows:1.A simple and practical method was established to simultaneously detect the residues of imidacloprid and fenpyroximate in the roots,stems,leaves and plants of celery by Ultra-high performance liquid chromatography-tandem mass spectrometry.The samples were extracted with acetonitrile and purified by some purification materials,such as C18,PSA,PestiCarb.The results showed that imidacloprid and fenpyroximate had a good linearity in the range of 0.005-0.5 mg/L.The average recoveries of imidacloprid in roots,stems,leaves and plants of celery were 77.15%-103.48%at three spiking levels from 0.05 mg/kg to 1.00 mg/kg with relative standard deviations(RSDs)of 1.40%-9.97%.The average recoveries of fenpyroximate in roots,stems,leaves and plants of celery were 77.35%～100.42%at three spiking levels from 0.05 mg/kg to 1.00 mg/kg with relative standard deviations(RSDs)of 1.13%～8.10%.The recovery and precision of this method was in accordance with the requirements of pesticide residue analysis.2.The results showed that the residue dynamics of imidacloprid and fenpyroximate in roots,stems,leaves,plants of celery were in accordance with the first-order kinetic model.When the dose of imidacloprid was 30 g a.i./hm2,the half-lives of imidacloprid in the roots,stems,leaves and plantsof celery were 7.28 d,3.65 d,5.51 d,and 3.83 d,respectively.When the dose of imidacloprid was 300 g a.i./hm,the half-lives of imidacloprid in the roots,stems,leaves and plants of celery were 6.10 d,2.89 d,4.06 d and 3.50 d,respectively.When the dose of fenpyroximate was 37.5 g a.i./hm,the half-lives of fenpyroximate in the roots,stems,leaves and plants of celery were 10.05 d,4.15 d,4.81 d and 4.42 d,respectively.When the dose of fenpyroximate was 375 g a.i./hm2,the half-lives of fenpyroximate in the roots,stems,leaves and plants of celery were 10.97 d,3.97 d,4.91 d and 5.72 d,respectively.The half-lives of imidacloprid and fenpyroximate in celery root were significantly longer than those in the stems,leaves,and plants of celery and those in celery stems were the shortest.3.The effect of imidacloprid and fenpyroximate on physiological and biochemical indexes of celery was studied.The celery was sprayed with imidacloprid and fenpyroximate,respectively.After 2 hours of the application,the content of soluble protein in celery increased by 1.04%-78.94%,the activity of peroxidase(POD)in celery increased by 7.36%-132.22%,the activity of superoxide dismutase(SOD)in the stems of celery increased by 11.22%-43.83%,and the activity of superoxide dismutase(SOD)in the leaves of celery decreased by 3.81%-34.26%compareing with the control group.The content of soluble protein,POD activity,and SOD activity were still significantly different from those of the control group on the 28th day,which indicated that imidacloprid and fenpyroximate had stress effect on celery.4.The effects of washing methods on the removal of imidacloprid and fenpyroximate in celery were studied.The results showed that the solution of water,salt,vinegar,bicarb,cleaning agents had removal effects on imidacloprid and fenpyroximate in celery.In general,the removal rate of imidacloprid was in order:cleaning agents>vinegar>salt>water>bicarb.The removal rate of fenpyroximate was in order:cleaning agents>vinegar>bicarb>salt>water.Considering the residue of the cleaning agent,vinegar was chosen as the best cleaning method.The best cleaning conditions for vinegar were A2B3C1,i.e.the cleaning time is 10 min,the temperature is 40 ℃,and the concentration of vinegar is 0.1%.