Non-targeted Screening of Phenylurea Pesticides in Apples by Ultra-high Performance Liquid Chromatography£­Quadrupole/Electrostatic Field Orbitrap High Resolution Mass Spectrometry

KeyWord:phenylurea herbicides  benzoylurea insecticides  electrostatic field orbitrap high resolution mass spectrometry  fragmentation pathway  non-targeted screening

Abstract:

      An ultra-high performance liquid chromatography£­quadrupole/electrostatic field orbitrap high resolution mass spectrometry£¨UPLC£­Q/Orbitrap HRMS£© was established for the non-targeted screening of phenylurea herbicides and benzoylurea insecticides in apples. Apple samples were extracted with acetonitrile£¬then purified by QuEChERS method. The purified solution was separated on an Acquity BEH C18 column£¨100 mm ¡Á 2.1 mm£¬1.7 ¦Ìm£© using a gradient mobile phase consisting of water£¨containing 0.1% formic acid £© and methanol£¬then analyzed by HRMS with electrospray ion source under positive ion mode. The 13 phenylurea herbicides and 9 benzoylurea insecticides were divided into four groups based on their structural differences. The secondary mass fragments of four typical standards in the four groups of phenylurea herbicides and benzoylurea insecticides were analyzed£¬and then£¬the regularities of the characteristic fragment ions and neutral loss fragments produced by collision induced dissociation of the phenylurea herbicides and benzoylurea insecticides were summarized. The main characteristic fragment ions of 9 herbicides such as chlorotoluron are m/z 72.044 59£¬and fragments can also be produced by neutral loss of dimethylamine£¨m/z 45.058 03£©. Four herbicides such as monolinuron lose neutral methanol £ÛCH3OH£Ý m/z 23.025 59 or hydrogen halide £ÛHR1£Ý£¨R=Cl£¬Br£¬F£©to produce fragment ions.The main characteristic fragment ions of seven fluorine atom substituted benzoylurea insecticides such as diflubenzuron are m/z 158.040 47 and m/z 141.015 00£¬and the neutral loss of 2£¬6-fluorobenzamide structure£ÛC8H3F2O2NH2£Ý£¨m/z 183.013 21£© can produce characteristic fragment ions. The main characteristic fragment ions of triflumuron and chlorobenzuron£¬which were chlorine atom substituted benzoylurea insecticides£¬are m/z 156.020 25£¬m/z 138.993 76 and m/z 113.015 28. A total of 12 apple samples collected from local supermarket in Beijing were screened by this non-targeted method. Chlorotoluron was identified and confirmed in one apple sample£¬which demonstrated that the method could achieve rapid and accurate non-targeted screening of phenylurea pesticides in apples. The proposed mass spectrometry fragmentation pathway in this study provides an important basis for the rapid identification and analysis of phenylurea and benzoylurea compounds with similar structural characteristics in complex systems.