QuEChERS结合UPLC-ESI-MS/MS分析吡蚜酮和异丙威SC在稻田中的残留特征

采用改良Qu ECh ERS法结合超高效液相色谱-电喷雾串联质谱法(UPLC-ESI-MS/MS)建立了吡蚜酮和异丙威在稻田环境中的残留分析方法,并通过田间模拟试验研究了吡蚜酮和异丙威悬浮剂(SC)在稻田中的残留沉积及持留特性。于稻田空白样品中添加吡蚜酮和异丙威至0.001~1 mg·kg-1的浓度进行添加回收率试验,样品采用乙腈提取和盐析净化,UPLC-MS/MS测定,分析结果表明,方法的平均回收率为75.2%~115.9%,相对标准偏差为2.6%~19.1%,两者在田水和植株(土壤)最低检测浓度(LOQ)分别达到0.001 mg·kg-1和0.005 mg·kg-1,说明该方法可用于检测稻田中痕量水平的吡蚜酮和异丙威。田间模拟试验结果表明,吡蚜酮·异丙威SC在稻田环境中的消解动态曲线符合一级动力学方程,吡蚜酮的半衰期为0.7~12.6 d,异丙威的半衰期为0.4~5.2 d,表明两者在环境中均属于易降解化合物。此外,与WG剂型相比,SC剂型的吡蚜酮·异丙威在植株上表现出更高的消解速率,而在土壤中则较低,显示剂型对农药的持留性具有显著影响。

Analysis of Residual Profiles of Pymetrozine and Isoprocarb SC in Paddy Field by QuEChERS Combined with UPLC-ESI-MS/MS

In this work, a rapid, accurate and sensitive method for determining the residues of pymetrozine and isoprocarb by UPLC-ESI-MS/MS combined modified-QuEChERS was developed, and was then applied to investigate the residual deposition and persistence of pymetrozine and isoprocarb SC in paddy soils under field conditions. The reliability of the method was evaluated by extracting the pesticide-free paddy samples spiked with authentic pesticides at various concentrations with acetonitrile, and purifying the extracts by salting-out and then analyzing pesticides by UPLC-ESI-MS/MS combined with external standard method. The recovery percentages of the pesticides ranged from 75.2% to 115.9% with the relative standard deviation(RSD) from 2.6% to 19.1%. The limit of quantification(LOQ) of both pesticides was 0.001 mg·kg^-1 in paddy field water and 0.005 mg·kg^-1 in rice-plant/soil, respectively, indicating that this method could be used to determine the trace amount of residual pymetrozine and isoprocarb in paddy field. In the field trial, the degradation curves of the pesticides fit the first-order kinetics. The half-life was 0.7~12.6 days for pymetrozine and 0.4~5.2 days for isoprocarb, suggesting that both pesticides were easily degradable compounds in the environment. In contrast to its WG-formulation, pymetrozine and isoprocarb SC showed relatively high dissipation rates in plant tissue, but relatively low in soil, showing the profound influence of formulation type of pesticides on their persistence in the agricultural ecosystem.