Lopes Renata P, de Urzedo Ana P F M, Nascentes Clésia C, Augusti Rodinei
Department of Chemistry, Federal University of Minas Gerais, Belo Horizonte/MG, Brazil, 31270-901!
Rapid Commun Mass Spectrom. 2008 Nov;22(22):3472-80. doi: 10.1002/rcm.3749.
The degradation of thiamethoxam (1) and imidacloprid (2), prototype neonicotinoid insecticides bearing a characteristic N-NO2 moiety in their structures, promoted by a number of zero-valent metals (Fe, Sn, Zn) upon ultrasonic irradiation in acidic aqueous solution (pH 2) was investigated. It was verified that thiamethoxam (1) and imidacloprid (2) are quickly and almost completely consumed under these experimental conditions (degradation >90% after a reaction time of 30 min) and that ultrasonic irradiation strongly enhances the degradation rate for both insecticides, especially when zinc and tin are employed. Based on the results from electrospray ionization mass (and tandem mass) spectrometry in the positive ion mode, degradation routes for both insecticides, comprising an initial NO2 --> NH2 reduction, were proposed. In addition, products from the dehydrochlorination of imidacloprid were also found to be formed under these conditions.
研究了在酸性水溶液（pH 2）中超声辐照下，多种零价金属（铁、锡、锌）对噻虫嗪（1）和吡虫啉（2）的降解作用。噻虫嗪（1）和吡虫啉（2）是结构中带有特征性N-NO₂部分的新型烟碱类杀虫剂原型。结果表明，在这些实验条件下，噻虫嗪（1）和吡虫啉（2）能快速且几乎完全被消耗（反应30分钟后降解率>90%），并且超声辐照显著提高了两种杀虫剂的降解速率，尤其是使用锌和锡时。基于正离子模式下的电喷雾电离质谱（和串联质谱）结果，提出了两种杀虫剂的降解途径，包括初始的NO₂→NH₂还原。此外，还发现吡虫啉在这些条件下会形成脱氯化氢产物。
