Efficient profiling of dimethoate impurities via integrated platform coupling chromatography with mass spectrometry...

Comprehensive profiling of impurities in organophosphorus pesticides, such as dimethoate, remains challenging due to their structural diversity, trace abundance, and analytical constraints. This can be overcome by integrating multiple analytical techniques to enhance impurity profiling of pesticides, particularly dimethoate, but little has so far been carried out in this field. Herein, a novel integrated analytical platform, synergizing high-performance liquid chromatography-diode array/charged aerosol detection (HPLC-DAD-CAD) with Orbitrap high-resolution mass spectrometry, empowered by MS-DIAL/SIRIUS artificial intelligence-driven annotation, was developed. The chromatographic conditions (column, mobile phase additive, organic phase, sample solvent, and gradient program) were optimized. The dual-detector synergy strategy simultaneously captured chromophoric and attenuated chromophoric species. Innovatively coupling MS-DIAL and SIRIUS identified three known impurities and 15 novel structures by a workflow leveraging spectral deconvolution, sub-ppm molecular formula prediction, and fragmentation modeling. Under the optimized setting, the method achieved a detection limit of 0.03 µg g⁻¹ and trace level sensitivity ≥0.01%. The fragmentation pathways were also demonstrated for a total of three key impurity classes (phosphorothioate esters, disulfide-linked compounds, and alkyl-modified derivatives), linking their formation with synthetic routes and storage degradation. Overall, the proposed extensible analytical framework establishes the foundation for pesticide impurity surveillance, strengthening reference material certification, production optimization, and agrochemical safety governance.