The Postharvest Disease Control And Residue Degradation Of Citrus Fruits Treated With New Fungicides

The determination of azoxystrobin, fludioxonil and imazalil residues in citrus fruit, decay control and residue levels during 447 Jinchen orange fruit with the treatment of three fungicides were conducted in this paper in order to provide a theoretical basis for the standard-setting of azoxystrobin and fludioxonil and pesticide storage citrus disease prevention, the main findings are as follows:1. A gas chromatography-electron capture detection (GC-ECD) method for determiniong azoxystrobin residue in Citrus is here presented, azoxystrobin residue was extracted by oscillation from citrus samples added n-hexane/ethyl acetate(1:1,v/v), without purification, extract solution being concentrated was injected in the GC column, quartz capillary column DB-5MS was used as separation column. Sample pre-treatment method is simple, The average recovery in orange pulp at fortification levels of 0.1-1.0mg/kg Azoxystrobin were in the range 78.4%-86.4% with relative standard deviations(RSD) between 1.7% and 4.5%. In Orange peel, the average recovery were 81.6%-90.2%, RSD 4.3%-13.9%, The minimum detectable concentration of azoxystrobin was 0.001mg/kg in orange samples, The method accords with the standards of determination of pesticide residues.2. A gas chromatography-electron capture detection (GC-ECD) method for determiniong imazalil residue in Citrus is here presented, imazalil residue was extracted by oscillation from citrus samples added n-hexane/ethyl acetate(1:1,v/v), without purification, extract solution being concentrated was injected in the GC column, quartz capillary column DB1701 was used as separation column. Sample pre-treatment method is simple, The average recovery in orange pulp at fortification levels of 0.1, 0.5, 1.0mg/kg imazalil were in the range 87.6%-102.2% with relative standard deviations(RSD) between 4.3%-7.6%. In Orange peel, the average recovery were 83.5%-96.2%, RSD 2.3%-14.5%, The minimum detectable concentration of imazalil was 0.01mg/kg in orange samples, The method accords with the standards of determination of pesticide residues.3. A liquid chromatographic method with ultraviolet detector(HPLC-UV) method has been established for the determination of fludioxonil residue in citrus. The determination of fludioxonil retention time was 5.10min using high-performance liquid chromatography with UV detection at 280nm, The mobile phase was methanol/water (75:25,v/v) with gradient elution. Samples added extracted acetone were shaked twice, after hexane liquid-liquid extraction, the extract was purified through Florisil-SPE column. The recoveries in orange peel, at spiked concentrations between1.0 and 5.0mg/kg, were between 69.7% and 78.0% with relative standard deviations ranging from 2.2 to 6.3%. The average recovery in orange pulp was 65.7%-73.0%, RSD 3.2%-5.8%. The minimum detectable concentration of fludioxonil in orange flesh and orange peel was 0.02mg/kg. The accuracy of the method is higher, the minimum detection limit of the requirements in line with demands for the determination of pesticide residues.4. The Fungistatic Test results indicate that the concentration 25-500mg/L pilot, the strongest fungicides against citrus Blue and Green Mold was fludioxonil and azoxystrobin/fludioxonil mixture the inhibitory rate of 100mg/L, 250 mg/L fludioxonil and 100mg/L, 250mg/L azoxystrobin/fludioxonil mixture to citrus Green Mold all amounted to 100%, azoxystrobin, Imazalil, Second. Under the same concentration 250 mg/L, the inhibiting effect of fludioxonil and azoxystrobin/fludioxonil mixture to citrus Blue Mold are the best, Imazalil, Second, Azoxystrobin, again.5. 447 Orange separately soaked with different concentrations fludioxonil, azoxystrobin, imazalil fungicides were stored in Ventilated Storage House more than three months, test results indicated that 250mg/L azoxystrobin, 500mg/L or 800mg/L fludioxonil immersion treatment can preferably control the occurrence of 447 Orange rot disease; The disease incidence of stem end rot and Brown rot, etc. for 500mg/L or 800mg/L fludioxonil immersion treatment are respectively 39.28%, 59.89%, They all lower than that of other treatment. It is visibile that fludioxonil on have better control effect on stem-rot, brown rot, etc.6. The residue-dynamics results of this fungicides indicated that azoxystrobin and imazalil can intake into the pulp through the peel, and the residual levels on peel is higher than the flesh; fludioxonil residue was not determined in pulp, it is probably related with non-system of Fludioxonil. The ultimate residual levels of the edible part are all very low after storage for 100 days, it is safety to eat. azoxystrobin and fludioxonil residue levels in 447 Orange peel also do not exceed the MRLs of foreign oranges, and the peel materials are suitable for peel integrated processing for raw materials.7. Fungicide residue degradation dynamics results in orange storage show that azoxystrobin and imazalil residue in citrus peel and flesh, fludioxonil residue in peel overall slow decreased at different degrees with the progress of the time. The half-life for Imazalil in pulp, the longest, was 55d, fludioxonil and azoxystrobin, the second, is respectly 50.6d 33.6d. The half-life for imazalil and fludioxonil in pulp was respectly 36.9d ,26.8d.