The Analysis Of Thidiazuron Residue In Strawberry And Its Effect On The Activity Level Of Related Enzymes In Strawberry

A liquid chromatography with tandem mass spectrometry(LC-MS/MS)method was established for the determination of thidiazuron in strawberry.The dissipation dynamics and terminal residues of thidiazuron in strawberry were carried out in several locations of China at 2017 and 2018.Strawberry samples were extracted with acetonitrile,salted out by sodium chloride,purified by ostadecylsilane,and detected by LC-MS/MS.The lineary of thidiazuron in strawberry was good with correlation coefficient > 0.99.Recoveries of thidiazuron in strawberry were 76.21%-105.08% with relative standard deviation of 1.09%-5.11%.The limit of detection was 0.001 mg/kg.In field and indoor trials,the half-lives of thidiazuron in strawberry were 3.96-5.56 d and 3.2-3.6 d,respectively,which indicated that thidiazuron was an easily-degraded pesticide.In the terminal residue trails,the residue concentrations of tthidiazuron were <0.001-0.028 mg/kg at harvest with spraying at two dosages of 0.75-1.125 g a.i./ha twice(interval of 7 d).The frozen storage stability results showed that the degradation rates of thidiazuron in strawberry under-20 ℃were less than 10% during 360 d.Another indoor simulation experiment was carried out to demonstrate the effect of thidiazuron on the related enzyme activities of strawberry.During the growth stage of strawberry,different concentrations(2,4,6,8,10 mg/kg)of thidiazuron were sprayed.The samples were collected at 2 h,1,2,3,5,7,10,14 and 21 d,and their antioxidant enzyme activities were determined.The results showed that the ascorbic acid content in strawberry increased significantly when the dose of thidiazuron was 2 mg/kg;the peroxidase activity increased in the strawberry sample treated with 2 mg/kg of thidiazuron on the first day after the application of thidiazuron,which was higher than the peroxidase activity in the controlled sample;in the first five days,the superoxide dismutase activity of the strawberry in the dose of 2 mg/kg was significantly lower than that of the controlled sample.