| At present the most effective means of controlling postharvest diseases of citrus was still using chemical preservatives. Commonly used in stored Valencia Orange were Carbendazim, Thiabendazole, Prochloraz, Iprodione, Sec-butylamine, Biphenyl, 2,4-Dichlorophenoxyacetic acid, etc. In these agents, some had application guidelines and standard operating procedures, some were common practices but there was no standard in the industry. This article Selected Valencia Orange as test material, established the residue analysis method of 2,4-Dichlorophenow,Carbendazim,Tiabendazole,Iprodione,Prochloraz; studied Carbendazim residue degradation in stored Valencia Orange, preliminary made the safety evaluation of in stored Valencia Orange, in hope to provide theory basis for safe application of Carbendazim.(1)In the present work, a rapid, simple and economic method based on dispersive solid phrase extraction(d SPE) in conjunction with ultrahigh-performance chromatography coupled with tandem mass spectrometry(UPLC-MS/MS) was developed for simultaneous determination of 2,4-Dichlorophenow,Carbendazim,Tiabendazole,Iprodione,Prochloraz in Valencia Orange.The optimum condition as follows: An aliquot(10.0g) of homogenized matrix were weighed into a 50 m L Teflon centrifuge tube with screw caps. Then 10 m L toluene and 10 m L Me CN were added. The mixtures were shaken vigorously for 20 min. Subsequently, 5.0g Na Cl were added into the mixtures. The tubes were capped and immediately intensively shaken for 1min,vortexed for 1min. After centrifuging the tubes at 5000 r/min for 5min, a 1.5m L aliquot was withdrawn gradually into a single-use 5m L centrifuge tube to be dried under a gentle nitrogen stream until dryness and reconstructed with 1.5m L Me OH. The tube was shocked intensively for 1min. Afterwards, the extracts was filtered through a 0.22μm nylon syringe filter and diluted 10 times,then transferred to an autosampler vial for UHPLC-MS/MS injection. The average recovery was between 74.89% and 112.02%;Relative standard deviation is under 10.00%.This method is simple, accurate and low cost, and suitable for the determination of five preservatives residues in Valencia Orange.(2) Based on the established method, aim to evaluate the quality and safety of Carbendazim in Valencia Orange during storage.25% powder of Carbendazim,250 times dilution, mixed into 1000 mg/L solution to soak Valencia Orange for 1 min. Then natural drying, then packaged by simple film, and store at 3℃,85% humidity environment, respectively sampling in 2h(primary sedimentary volume), 1d and 2d, 3d, 5d, 7d, 10 d, 14 d, 21 d, 30 d, 45 d, 60 d. Three samples randomly, chopped and blending, retention samples according to the four points method, take 10.0g each parallel sample. At the same time, make blank control.The results showed that Carbendazim in Valencia Orange during storage has played a good preservation effect. After 45 days, the Carbendazim residue in peel was less than 5.00mg/kg, the maximum residue is 4.46mg/kg; The Carbendazim residue in all fruit was always less than 3.00mg/kg; The Carbendazim residue in pulp was always less than 1.00mg/kg, lower than the maximum residue limits by GB2763-2014. As a result, the 25% powder, soaked by 250 times liquid(1000 mg/kg) for 1min, after 45 days the Carbendazim residue can be reduced to safe levels, can be classified as security interval. |
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