噻虫嗪及其代谢物噻虫胺在节瓜中的消解动态及初步膳食风险评估

为明确噻虫嗪在节瓜上的残留行为，于2015年在广东和上海两地进行了噻虫嗪在节瓜上的规范田间残留试验，建立了节瓜中噻虫嗪及其代谢物噻虫胺残留量的高效液相色谱-串联质谱 (HPLC-MS/MS) 检测方法。样品用乙腈提取，经氨基固相萃取小柱净化，HPLC-MS/MS 检测，外标法定量。结果表明:噻虫嗪在节瓜上的消解半衰期为4.98~5.84 d；采用25%噻虫嗪水分散粒剂 (WG)，分别按有效成分75和112.5 g/hm2 的剂量于幼果期开始施药，施药2~3次，每次施药间隔期为7~10 d，距最后一次施药后3、5、7 d 采样测定，节瓜中噻虫嗪和噻虫胺的残留量分别为0.010~0.422 mg/kg和 <0.010~0.020 mg/kg。膳食摄入风险初步评估结果显示:其风险商值 (RQ) 为0.044，表明噻虫嗪的长期膳食摄入风险较低。目前中国尚未制定噻虫嗪在节瓜上的最大允许残留限量 (MRL) 标准，根据试验结果，建议中国可将噻虫嗪在节瓜上的MRL值暂定为1 mg/kg。

Dissipation dynamics and preliminary dietary risk assessment of thiamethoxam and clothianidin in Benincasa hispida

The residue behaviors of thiamethoxam in Benincasa hispida Cogn. var. chieh-qua How (chieh-qua) were investigated. The residue field trials of thiamethoxam were designed and conducted in Guangdong and Shanghai in 2015. An effective method was developed for the determination of the thiamethoxam and clothianidin. The chieh-qua samples were extracted by acetonitrile, purified with aminopropyl solid phase extraction and detected using HPLC-MS/MS (high performance liquid chromatography-tandem mass spectrometry). The dissipation and terminal residues of thiamethoxam and clothianidin in chieh-qua samples in Guangdong and Shanghai were determined based on the above analytical method. The results indicated that the half-lives of thiamethoxam in chieh-qua was 4.98-5.84 d. The chieh-qua was sprayed 2 to 3 times with 7-10 days spray interval using 25% WG at the dosage 75 and 112.5 g/hm² during the young fruit period. The samples were collected 3 to 7 days after the last spray. The terminal residues of thiamethoxam and clothianidin were 0.010-0.422 mg/kg and <0.010-0.020 mg/kg, respectively, which were determined by the conditions above. The risk quotients (RQ) was 0.044, which revealed its low risk. According to the results, it is suggested that the MRL of thiamethoxam in chieh-qua in China should be set as 1 mg/kg.