电喷雾质谱中β-羟基诱导偶氮裂解机理研究及在食品偶氮染料筛查鉴定中的应用

食品的偶氮染料污染是当前危害人体健康的一项重要风险，裂解机理是ESI-MS鉴定有机分子结构的核心内容和研究热点，而研究偶氮裂解机理是ESI-MS分析鉴定偶氮染料污染种类，控制风险的关键步骤。本课题提出了“腙式-偶氮式”竞争性断裂的偶氮裂解机理，拟以苏丹红和偶氮磺酸类染料为模板分子，使用密度泛函理论计算、Q-trap MS和Orbitrap HRMS质谱，研究ESI-MS中β-羟基诱导偶氮裂解的质子化位点，碎片结构和键断裂位置，归纳裂解规律，验证这一新颖的裂解机理；再通过氢/氘交换、同位素标记试验，取代基效应研究和理论计算的方法，进一步阐明偶氮竞争性裂解的平衡过渡态和影响因素。本项目即丰富了偶电子离子的裂解机理和规律，加深了对离子裂解过程中基本反应推动力的认识，也为建立食品中偶氮染料的裂解模型和质谱快速检测方法奠定了理论和实验基础。

It is significant and necessary to explore and summary the fragmentation mechanism of protonated or de-protonated molecules in ESI-MS for the structural analysis of organic compounds. Azo dyes contamination is one of the major food pollutions now. The study on fragmentation mechanism of azo double bond in ESI-MS will improve and promote the identification of illegal azo dyes in foods. This research proposed a new fragmentation mechanism of azo dyes induced by β-hydroxy, namely the competitive “azo-hydrozone” tautomeric cleavage. Based on a series of sudan and sulphonated azo dyes as models, the fragmentation pathways and characteristic ions of these compounds will be explored and summarized using Q-trap MS and Orbitrap HRMS. The “azo-hydrozone” competitive cleavage model will further be witnessed by H/D exchange, D-labeling experiments, substituent effects and DFT theoretical calculation. These researches will provide a basis for developing MS-based methods of detecting or screening a class of azo dyes in foods.