UPLC-MS/MS测定菠萝中除草定的残留行为

为了明确除草定在菠萝上的残留行为，以及为中国制定除草定在菠萝上的最大残留限量提供数据支撑，笔者采用田间试验方法研究了除草定在菠萝和土壤中的残留与降解行为，采用UPLC-MS/MS进行定性定量分析，研究了前处理方法中不同的净化条件（液液分配萃取溶剂、固相萃取小柱、淋洗液、淋洗体积）对除草定检测分析的影响，并确定最优前处理方法条件。除草定的最小检出量为1×10^-12 g，菠萝和土壤中的最小检出浓度为5×10^-3 mg/L。当添加浓度为0.01~1 mg/L时，在菠萝和土壤中的平均添加回收率分别为85.1%~86.5%、84.0%~85.5%；相对标准偏差分别为3.46%~6.78%、2.74%~4.54%，符合农药残留分析检测要求。田间试验结果表明，除草定在土壤中的降解符合一级动力学方程，其降解半衰期为8.2~11.1天（小于30天），属于易降解农药；按低剂量（有效成分4800 g/hm²）施药1、2次，收获期菠萝全果中除草定的残留量为＜0.01~0.01 mg/kg，菠萝果肉中除草定残留量均＜0.01 mg/kg。在菠萝中的最终残留量均低于日本和澳大利亚规定的最大残留限量(0.05、0.04 mg/kg)。

Determination of Bromacil Residues in Pineapple by UPLC-MS/MS

In order to evaluate the environmental behavior of bromacil in pineapple, and provide the date of the MRL of bromacil in pineapple in China. Residue dynamics of bromacil in pineapple and soil was studied by field trial, and made qualitative and quantitative analysis by UPLC- MS/MS. In order to optimize the experimental conditions, the effects of different clenaning conditions (extraction solvent, SPE, elution solvent, elution volume) were investigated. The limit of detection was estimated to be 1×10^-12 g. The minimum concentration of detection in pineapple and soil was 5×10^-3 mg/L. The average recoveries of bromacil in pineapple and soil were 85.1%-86.5%, 84.0%-85.5% with relative standard deviation were 3.46%-6.78%, 2.74%-4.54%，respectively when the fortified concentration was 0.01-1 mg/L. It was fitted for the demand of pesticide residue analysis and detection. The trial results showed that the dissipation of bromacil in soil was in conformity with the first- order dynamic equation, the half- lives were 8.2- 11.1 days in soil. The terminal residues of bromacil in the whole fruits and flesh were＜0.01-0.01 mg/kg and＜0.01 mg/kg, respectively when the pineapple was sprayed once to twice according to the recommended dosage 4800 g/hm². The terminal residues of bromacil were all below the MRLs of Japan (0.05 mg/kg) and Austiralian (0.04 mg/kg) at harvest time.