Systemic insecticides such as neonicotinoids are widely used in seed coating practices for pest control in many crops, e.g., corn. Their success is due to their ability to protect the whole plant, from the roots to the upper leaves, but their use at high amounts is causing possible adverse effects on non-target animals exposed to contaminated pollen, nectar, leaves, and dust emitted during sowing. In 2018, the European Union banned some neonicotinoids and fipronil as seed coating insecticides in open fields. Consequently, the methylcarbamate methiocarb and less-toxic neonicotinoids, e.g., thiacloprid, have been authorized and largely used as alternative pesticides for corn seed coating. Here, an analytical protocol based on QuEChERS extraction/purification procedure and analysis by liquid chromatography-mass spectrometry has been optimized for the identification and the quantification of methiocarb, thiamethoxam, thiacloprid, and their metabolites in guttation drops, the xylem fluid excreted at leaf margins, and in leaves of corn plants grown from coated seeds. Although methiocarb is a non-systemic pesticide, we unexpectedly found high concentrations of its metabolites in both guttations and leaves, whereas methiocarb itself was below detection limits in most of the samples. The methiocarb main metabolite, methiocarb sulfoxide, was found at a mean concentration of 0.61 ± 1.12 µg mL⁻¹ in guttation drops and 4.4 ± 2.1 µg g⁻¹ in leaves. Conversely, parent compounds of neonicotinoids (thiamethoxam, thiacloprid) are systemically distributed in corn seedlings. This result raises safety concerns given that methiocarb sulfoxide is more toxic than the parent compound for some non-target species.

诸如新烟碱之类的内吸性杀虫剂广泛用于种子包衣实践中，以控制许多作物（例如玉米）中的害虫。它们的成功归功于它们从根部到上部叶片都能保护整个植物的能力，但是大量使用它们会对暴露于受污染的花粉，花蜜，叶子和粉尘的非目标动物造成可能的不利影响。播种。2018年，欧盟禁止在露天田地使用一些新烟碱和氟虫腈作为种子包衣杀虫剂。因此，氨基甲酸甲酯，甲硫威和毒性较小的新烟碱（如噻虫啉）已被批准，并广泛用作玉米种子包衣的替代农药。这里，已优化基于QuEChERS提取/纯化程序和液相色谱-质谱分析的分析规程，用于鉴定和定量滴定滴中的甲硫威，噻虫嗪，噻虫啉及其代谢产物，木质素液在叶边缘排泄，以及从被覆种子生长的玉米植物的叶子中。尽管甲硫威是一种非系统性农药，但我们出乎意料地在肠道和叶片中发现了其代谢产物的高浓度，而在大多数样品中甲硫威本身的含量都低于检测极限。甲硫威的主要代谢产物甲硫威亚砜的平均浓度为0.61±1.12 µg mL 木质部流体在叶边缘和从被覆种子生长的玉米植株的叶片中排出。尽管甲硫威是一种非系统性农药，但我们出乎意料地在肠道和叶片中发现了其代谢产物的高浓度，而在大多数样品中甲硫威本身的含量都低于检测极限。甲硫威的主要代谢产物甲硫威亚砜的平均浓度为0.61±1.12 µg mL 木质部流体在叶边缘和从被覆种子生长的玉米植株的叶片中排出。尽管甲硫威是一种非系统性农药，但我们出乎意料地在肠道和叶片中发现了其代谢产物的高浓度，而在大多数样品中甲硫威本身的含量都低于检测极限。甲硫威的主要代谢产物甲硫威亚砜的平均浓度为0.61±1.12 µg mL滴状滴为^-1，叶子滴为4.4±2.1 µg g ^-1。相反，新烟碱类的母体化合物（噻虫嗪，噻虫啉）全身分布在玉米幼苗中。鉴于甲硫碳亚砜比母体化合物对某些非目标物种的毒性更大，因此该结果引起了安全隐患。