超高效液相色谱-串联质谱法分析茶叶生长加工冲泡过程中螺螨酯的残留迁移降解

茶叶是我国重要的经济作物之一，随着产业规模不断扩大和病虫害频发，化学农药多用于快速防治茶园病虫害。但是，茶园登记使用的农药种类较少，长期单一频繁使用后，茶园害虫易产生抗药性，防治效果降低，导致农药用量增加，由此带来的茶叶中农药残留问题引起广泛关注。因此，寻找并评估新的茶园替代农药在茶叶上的残留行为和最大残留限量标准具有重要意义。本文将优化的QuEChERS前处理方法与超高效液相色谱-串联质谱（UPLC-MS/MS）相结合，建立了茶鲜叶、红茶、绿茶、红茶汤和绿茶汤中螺螨酯的残留分析方法。结果表明：在0.005~2.5 mg/L浓度范围内，不同基质的螺螨酯标准曲线相关系数R²在0.993 6以上，检出限（LODs）均小于0.002 mg/L；4个不同添加水平下，螺螨酯的平均回收率为78.8%~107.5%，相对标准偏差 (RSD)为1.3%~13.9%，在茶鲜叶、红茶和绿茶、红茶汤和绿茶汤中的定量限（LOQ)分别为0.002 mg/kg、0.005 mg/kg和0.000 2 mg/L。利用该方法研究了螺螨酯在茶叶生长加工及冲泡过程中的迁移降解规律发现，螺螨酯在浙江茶鲜叶上的降解半衰期为3.29天；从茶鲜叶经过加工后到红茶和绿茶的螺螨酯残留量显著降低，分别降低33.6%~51.8%和22.7%~63.4%；螺螨酯在红茶汤和绿茶汤中的浸出率较低，3次总浸出率分别为1.8%~4.3%和1.5%~2.8%。通过膳食风险评估发现，人体饮茶中的螺螨酯最大摄入量为0.000 069 mg/kg·d bw，仅为螺螨酯ADI值的0.69%；全膳食风险评估表明，螺螨酯的国家估算每日摄入量（NEDI）是0.362 2 mg，日允许摄入量0.63 mg，风险概率57.49%。因此，将我国茶叶中螺螨酯的最大残留限量值设定为10 mg/kg，对人体膳食摄入风险较低。

Residual Migration and Degradation of Spirodiclofen During Tea Growing,Processing and Brewing by Ultra-Performance Liquid Chromatography-Tandem Mass Spectrometry

Tea is one of important economic crops in China. With the continuous expansion of its planting scale and frequent occurrence of diseases and insect pests, chemical pesticides are mostly used to quickly prevent and control diseases and insect pests in tea gardens. However, there are a few kinds of pesticides registered in tea garden. After long-term of single and frequent usage, pests in tea garden are easy to produce resistant, resulting in the control effects reduced and the pesticide usage increased, and a widespread concern is attracted for the pesticide residues in tea. Therefore, it is of great significance to find a new pesticide in tea garden and to evaluate the residue behavior of the pesticide and to set the maximum residue limit standard on tea. In this study, a residue analysis method of spirodiclofen in fresh tea leaves, black tea, green tea, black tea infusion and green tea infusion was established by an optimized QuEChERS pretreatment combined with ultra-performance liquid chromatography-tandem mass spectrometry (UPLC-MS/MS). The correlation coefficient (R²) of spirodiclofen in the standard curves of solvent and different matrices were above 0.993 6 at the concentration range of 0.005-2.5 mg/L, and the detection limits (LODs) were all less than 0.002 mg/L. The recoveries of spirodiclofen ranged from 78.8% to 107.5%, and the relative standard deviations (RSDs) were 1.3%-13.9% for four different spiked concentrations, the quantification limits (LOQs) of spirodiclofen in fresh tea leaves, black tea and green tea, and black tea infusion and green tea infusion were 0.002 mg/kg, 0.005 mg/kg and 0.000 2 mg/L, respectively. This method was used to analyze the migration and degradation of spirodiclofen during tea growing, processing and brewing, it was found that the degradation half-life of spirodiclofen on fresh tea leaves in Zhejiang was 3.29 day, after processing, from fresh tea leaves to black tea and green tea, the residues of spirodiclofen were significantly reduced 33.6%-51.8% and 22.7%-63.4%, respectively. The leaching rates of spirodiclofen in black tea infusion and green tea infusion were very low, with the total leaching rates were 1.8%-4.3% and 1.5%-2.8%, respectively. The dietary risk assessment showed that the maximum intake of spirodiclofen in human drinking was 0.000 069 mg/kg·d bw, which was only 0.69% of the ADI value of spirodiclofen, and the national estimated daily intake (NEDI) of spirodiclofen was 0.362 2 mg, the acceptable daily intake was 0.63 mg, so the risk probability was 57.49%. Thus, the maximum residue limit (MRL) of spirodiclofen in tea can be set at 10 mg/kg in China, which has only a lower risk for human tea intake.