Tang Shouying, Meng Xiurou, Wang Yongkang, Shi Xueqin, Feng Tianyou, Hu Deyu, Zhang Yuping
State Key Laboratory Breeding Base of Green Pesticide and Agricultural Bioengineering, Key Laboratory of Green Pesticide and Agricultural Bioengineering, Ministry of Education, Guizhou University, Guiyang 550025, China.
Clinical Laboratory, Qufu City Center for Disease Control and Prevention, Jining 273100, China.
Foods. 2021 Oct 28;10(11):2615. doi: 10.3390/foods10112615.
Dimethacarb is a carbamate insecticide developed in China that contains 3,5-dimethylphenyl methylcarbamate (XMC) and 3,4-dimethylphenyl methylcarbamate (MPMC) isomers. Dimethacarb has been registered for use in rice in China, but no residue or degradation of dimethacarb in rice has been reported and the maximum residue limits (MRLs) for rice have not been established. A versatile high-performance liquid chromatography-tandem mass spectrometry (HPLC-MS/MS) method was developed with modified QuEChERS sample preparation to determine two isomers of dimethacarb in rice. The average recovery of XMC and MPMC in brown rice, rice husk, and rice straw ranged from 71.69 to 100.60%, with spike levels of 0.01 to 1 mg/kg and relative standard deviations (RSDs) of 0.21 to 8.41%. Field experiments showed that the half-lives of XMC and MPMC in rice straw were 4.08 to 4.23 days and 3.48 to 3.69 days, respectively. Final residues of XMC and MPMC in rice husk after 21 days of spraying at six sites ranged from 0.23-2.65 mg/kg and 0.06-1.10 mg/kg, and <0.01-0.16 mg/kg and <0.01-0.04 mg/kg in brown rice. The ratio of XMC to MPMC content in the rice husk differed from the original 50% dimethacarb EC, indicating the difference in the degradation rate of XMC and MPMC. The estimated risk quotient (RQ) for both XMC and MPMC was less than 30%. These data for residues from six representative locations could provide a reference for establishing the MRL of dimethacarb in rice.
速灭威是中国研发的一种氨基甲酸酯类杀虫剂，含有3,5-二甲基苯基甲基氨基甲酸酯（XMC）和3,4-二甲基苯基甲基氨基甲酸酯（MPMC）两种异构体。速灭威已在中国登记用于水稻，但尚未见有关其在水稻中的残留或降解报道，也未制定水稻中的最大残留限量（MRLs）。本文建立了一种通用的高效液相色谱-串联质谱（HPLC-MS/MS）方法，结合改进的QuEChERS样品前处理方法，用于测定水稻中速灭威的两种异构体。糙米、稻壳和稻草中XMC和MPMC的平均回收率在71.69%至100.60%之间，加标水平为0.01至1 mg/kg，相对标准偏差（RSDs）为0.21%至8.41%。田间试验表明，稻草中XMC和MPMC的半衰期分别为4.08至4.23天和3.48至3.69天。在六个地点喷施21天后，稻壳中XMC和MPMC的最终残留量分别为0.23 - 2.65 mg/kg和0.06 - 1.10 mg/kg，糙米中分别为<0.01 - 0.16 mg/kg和<0.01 - 0.04 mg/kg。稻壳中XMC与MPMC含量之比与原50%速灭威乳油不同，表明XMC和MPMC的降解速率存在差异。XMC和MPMC的估计风险商（RQ）均小于30%。来自六个代表性地点的这些残留数据可为制定水稻中速灭威的最大残留限量提供参考。
