关键词: 高分辨气相色谱质谱联用, 基质辅助激光解吸电离质谱成像, 抑霉唑, 农药残留, 时空分布

Abstract: A multidimensional analytical method based on high-resolution gas chromatography-mass spectrometry (GC-MS) combined with matrix-assisted laser desorption ionization mass spectrometry imaging (MALDI-MSI) was established for the systematic analysis of the spatiotemporal migration and distribution characteristics of the triazole fungicide Imazalil within root tuber crops. Using cherry radish as the model crop, a quantitative analysis was first performed through fine layer-by-layer sectioning (approximately 1.5 mm per layer), combined with the QuECHERS pretreatment technique and a matrix-matched external standard method. The results revealed significant differences in the depth distribution of Imazalil in radishes depending on the exposure time: after 2 h of exposure, a high concentration (approximately 30.6 mg/kg) was detected in the surface layer, decreasing rapidly inward. As the exposure time extended to 5 h, 10 h, and 24 h, Imazalil gradually penetrated into deeper tissues, with the inner layer concentration increasing significantly and the overall concentration gradient becoming more gradual, demonstrating a dynamic migration characterized by"epidermal adsorption; layer-by-layer penetration". Furthermore, MALDI-MSI was utilized for high spatial resolution imaging analysis of radish cross-sections, visually presenting the two-dimensional distribution characteristics of Imazalil within the tissue structure. The imaging results showed the strongest signals in the epidermis and cortex regions, gradually weakening inward, reflecting the slow diffusion and accumulation process of Imazalil in the tissues. The spatial distribution trend obtained from MALDI imaging was highly consistent with the quantitative results from GC-MS. Together, these two approaches validated the migration mechanism of Imazalil in radish from both quantitative and spatial dimensions, characterized by "from surface to inside, decreasing layer by layer, and gradually penetrating." This study achieved the dynamic visualization and in-depth quantitative analysis of the spatiotemporal distribution of pesticides in root crops, providing a new technical approach and experimental basis for revealing pesticide migration behavior in plants, and offering scientific support for agricultural product safety assessment and pesticide residue risk control.

Key words: High-resolution gas chromatography-mass spectrometry, Matrix-assisted laser desorption/ionization mass spectrometry imaging, Imazalil, Pesticide residues, Spatial and temporal distribution