The application of in-source fragmentation in ultra-high performance liquid chromatography-electrospray ionization -tandem mass spectrometry for pesticide residue analysis

Abstract

In this study, in-source fragmentation in ultra-high performance liquid chromatography-electrospray ionization-tandem mass spectrometry (UHPLC-ESI-MS/MS) was investigated and applied for pesticide residue analysis. Over 400 pesticides were tested, among which 26 pesticides were found to be sensitive to in-source fragmentation, producing 33 in-source fragments. The fragment pathways were studied and severe in-source fragmentation was observed due to the cleavage of C-O bond of carbamate, phosphate, ester, and ether groups, especially for isocarbophos and methoprene, leading to false negative results. High source temperatures could significantly increase the extent of in-source fragmentation. A multiple reaction monitoring (MRM) based multiresidue method was established for the pesticide residue analysis in vegetables and fruits, applying both pesticides and in-source fragments as precursors. The quantification ability of the method was validated and compared in terms of recovery, linearity, and the limit of quantification. In-source fragmentswere found to be more suitable than their parent pesticides as precursor ions for MRM analysis.