PDF《RESIDUE AND ANALYTICAL ASPECTS》

Difenoconazole

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10 DIFENOCONAZOLE (224) RESIDUE AND ANALYTICAL ASPECTS Difenoconazole was evaluated for the first time by JMPR

2007 when an acceptable daily intake (ADI) of 0C0.01 mg/kg bw and an acute reference dose (ARfD) of 0.3 mg/kg bw were established. In 2007, 2010,

2013 and

2015 the JMPR evaluated the compound for residues and recommended a number of maximum residue levels. The definition of the residue for compliance with MRL and for dietary intake for plant commodities is parent difenoconazole, while for animal commodities it is defined as sum of difenoconazole and 1-[2-chloro-4-(4-chloro-phenoxy)-phenyl]-2-(1,2,4-triazol)-1-yl-ethanol (CGA205375), expressed as difenoconazole. The residue is fat-soluble. The current Meeting received additional analytical methods, storage stability data for dried beans and oranges, processing data for rice, GAP information and residue trial data for uses on pome fruits (apples, pears), blueberries, strawberries, guava, dragon fruit, watermelon, chili peppers, sweet corn, pulses (beans, peas (except soya bean) and chickpeas), ginseng, globe artichoke, rice and coffee beans. Methods of analysis The Meeting received additional information on analytical methods for difenoconazole in plant matrices. Method AG-676 employs refluxing with methanol/conc. ammonium hydroxide (8:2 v/v). Clean-up is performed by liquid-liquid partitioning against hexane followed by acetonitrile and SPE on silica and phenyl. Residues are determined by GC-NPD with a LOQ of 0.01 mg/kg. The QuEChERS method employs shaking with acetonitrile/water (1/1, v/v) and clean-up by dispersive SPE with PSA. Residues are determined by LC-MS/MS using the ion transitions m/z 406→251, 406→337 with a LOQ of 0.005 mg/kg. Method REM 147.08 employs refluxing with methanol/conc. ammonium hydroxide (8:2 v/v). Clean-up is performed by SPE on a HLB cartridge. Residues are determined by LC-MS/MS using the ion transition m/z 406→251 with a LOQ of 0.01 mg/kg. The Modified Korean Food Code Method employs homogenization with acetone and clean- up by liquid-liquid partitioning against dichloromethane followed by SPE on a silica column. Residues are determined by LC-UV and LC-MS/MS using the ion transitions m/z 406→251, 406→337 with a LOQ of 0.03 mg/kg. The Meeting concluded that the presented methods were sufficiently validated and are suitable to measure difenoconazole in plant commodities. Stability of pesticides in stored analytical samples Information provided for the

2007 JMPR indicated that difenoconazole residues were stable at approximately -20 °C for

2 years in matrices with high oil content, high water content matrices, high starch matrices and wheat forage and straw. The Meeting received additional information on storage stability of difenoconazole in acidic and high protein content matrices, demonstrating a storage stability of at least

9 months. Results of supervised residue trials on crops Pome fruits Difenoconazole is registered in the USA for use on pome fruit (apple and pear). The critical GAP involves five pre-harvest foliar applications at a rate of

77 g ai/ha with a

7 day interval and

14 days Difenoconazole

120 PHI. After harvest, subsequent post-harvest treatments using either dip or drench at

30 g ai/hL or spraying at 1.3 g ai/tonne are applied. The Meeting received supervised field trial data from the USA on apples and pears matching the cGAP. In pome fruit (apples and pears) the ranked residues of difenoconazole following GAP treatment (±25%) were: Dip treatment (n=9): 0.59, 0.66, 0.85, 0.90, 0.93, 1.0, 1.1(3) mg/kg. Drench treatment (n=9): 0.56, 0.76, 0.85, 0.86, 1.1(2), 1.2, 1.3, 2.6 mg/kg. Spray treatment (n=9) 0.39, 0.56, 0.59, 0.60, 0.63, 0.66, 0.78, 1.1, 1.4 mg/kg. The Meeting estimated a maximum residue level of