Construction of Non-Target Screening Method for Pesticides in Milk and Dairy Products Based on Mass Spectrometry Fracture Mechanism

A method for non-target screening of pesticide residues in dairy products by ultra-high performance liquid chromatography-hybrid quadrupole-Orbitrap mass spectrometry ( UHPLC-Q-Orbitrap MS ) was developed. A database of pesticide residue standards was established for the experimental application of data-dependent acquisition mass spectrometry technology. Subsequently, the fragmentation mechanism of eight classes of 100 pesticides was studied , and the characteristic fracture fragments of different classes of pesticides were obtained. By combining pesticide fragmentation with the pesticide residue standard database , a nondirectional screening method based on data-independent acquisition mass spectrometry was developed. Finally , the established method was applied to the non-directional analysis of pesticide residues in 93 batches of pasteurized milk and ultra-high temperature instant sterilized milk. As a result, pre-undetected azoxystrobin (2. 3 mu g/kg) and chlorthiamide (6. 1 mu g/kg) were detected in the samples , with the relative standard deviations of 2. 3% and 1.2% . The high-resolution non-target screening analysis method established here can provide effective technical means for rapid screening and identification of pesticides in dairy products.