非衍生化分散固相萃取结合液相色谱-串联质谱测定茶叶和花椒中草铵膦、草甘膦及其代谢物残留

Non-derivatized dispersive solid-phase extraction coupled with LC-MS/MSfor the determination of residues of glufosinate,glyphosate and theirmetabolites in tea and Zanthoxylum bungeanum

本研究建立了一种无需衍生化、采用分散固相萃取(d-SPE)结合液相色谱-串联质谱(LC-MS/MS)检测茶叶和花椒中草铵膦及其代谢物NAG和MPPA、草甘膦及其代谢物AMPA残留的方法。样品经10 m L水+10 m L 1%甲酸-甲醇提取后,利用复合型多壁碳纳米管(C-MWCNTs)为核心净化材料的d-SPE技术进行处理,以提高目标化合物与基质的分离效率,减少基质干扰,结合液相色谱-串联质谱(LC-MS/MS)检测。以0.7%甲酸溶液和0.7%甲酸-乙腈作流动相,阴离子极性色谱柱(2.1 mm×100 mm,5μm) 40℃分离,负离子模式下动态多反应监测(d MRM),基质外标法定量。结果显示:5种化合物在该仪器条件下峰形尖锐,分离良好,在0.01~2μg/m L范围内线性良好,在茶叶和花椒中的决定系数(R2)分别为R2﹥0.9987和R2﹥0.9992,定量限(LOQ)分别在0.03~0.10 mg/kg之间和0.03~0.16 mg/kg之间。在0.25、0.50、1.0 mg/kg 3个添加水平下,草铵膦、草甘膦及3种代谢物在茶叶(藏茶)中的平均回收率为61%~105%,相对标准偏差(RSD)为0.22%~13%;在花椒(红花椒)中的平均回收率为78%~115%,RSD为0.12%~7.5%。该方法前处理过程无需衍生,净化步骤简单,仪器检测时间短,回收率和精密度均符合方法验证要求,适用于大批量茶叶和花椒中草铵膦、草甘膦及3种代谢物的快速检测。

An analytical method without the need for derivatization was established in this study,employing dispersive solid-phase extraction(d-SPE)combined with liquid chromatography-tandem mass spectrometry(LC-MS/MS)for the direct determination of residues of glufosinate,glyphosate and their metabolites(NAG,MPPA,AMPA)in tea and Zanthoxylum bungeanum.After extraction with 10 mL of deionized water and 10 mL of 1%formic acid-methanol solution,samples were processed using d-SPE with composite multi-walled carbon nanotubes(C-MWCNTs)as the core purification material to enhance the separation efficiency between the target compounds and the matrix and to reduce matrix interference.Finally,detection of five target compounds was achieved using LC-MS/MS.The mobile phases were water with 0.7%formic acid and acetonitrile with 0.7%formic acid.The separation was performed on an anionic polar column(5μm,2.1 mm×100 mm)at 40℃.The final extracts were detected using the dynamic multiple reaction monitoring(dMRM)method in negative mode and were quantified using external matrix-matched calibration curves.The results showed that the five analytes had sharp peak shapes and good separation under the instrument conditions,and the linearity was good in the range of 0.01-2μg/mL.The coefficients of determination(R2)were higher than 0.9987 and 0.9992 for tea and Z.bungeanum,respectively.The limits of quantification(LOQ)of the five compounds in tea and Z.bungeanum were 0.03-0.10 mg/kg and 0.03-0.16 mg/kg,respectively.At three spiked levels of 0.25,0.50 and 1.0 mg/kg,the average recoveries of glufosinate,glyphosate and their metabolites in tea(Tibetan tea)ranged from 61%to 105%with relative standard deviations(RSD)from 0.22%to 13%,and were 78%-115%in Z.bungeanum(red Z.bungeanum)with RSD of 0.12%-7.5%.The sample preparation process of this method does not require derivatization,the cleanup steps are simple,the instrumental running time is short,and the recoveries and precision met the requirements of method validation.It is suitable for the rapid determination of glufosinate,glyphosate and their metabolites(NAG,MPPA,AMPA)in large quantities of tea and Z.bungeanum.