Yang Shuiping, Ding Jianhua, Zheng Jian, Hu Bin, Li Jianqiang, Chen Huanwen, Zhou Zhiquan, Qiao Xiaolin
Department of Applied Chemistry, East China Institute of Technology, Fuzhou, 344000 PR China.
Anal Chem. 2009 Apr 1;81(7):2426-36. doi: 10.1021/ac900063u.
Without any sample pretreatment, trace amounts of melamine in various milk products were rapidly detected noting the characteristic fragments (i.e., m/z 110, 85, and 60) in the MS/MS spectrum of protonated melamine molecules (m/z 127) recorded by using surface desorption atmospheric pressure chemical ionization mass spectrometry. Signal responses of the most abundant ionic fragment (m/z 85) of protonated melamine were well correlated with the amounts of melaime in milk products, showing a dynamic range about 5 orders of magnitude. The limit of detection (LOD) was found to be 3.4 x 10(-15) g/mm(2) (S/N = 3) for the detection of pure melamine deposited on the paper surface, which was much lower than that for detection of melamine in powdered milk (1.6 x 10(-11) g/mm(2), S/N = 3) or liquid milk (1.3 x 10(-12) g/mm(2), S/N = 3). The significant difference in LOD was ascribed to the relatively strong molecular interactions between melamine and the matrix such as proteins in the milk products. As demonstrated using desorption electrospray ionization (DESI) for melamine detection, weakening the molecular interaction between analytes and proteins is proposed as a general strategy to improve the sensitivity of ambient mass spectrometry for direct detection of analytes bound in protein matrixes. The relative standard deviation (RSD) and the recovery of this method were found to be 5.2 approximately 11.9% and 87 approximately 113%, respectively, for the detection of melamine in milk products. A single sample analysis was completed within a few seconds, providing a particularly convenient way to rapidly screen melamine presence in milk products.
在不进行任何样品预处理的情况下，通过表面解吸常压化学电离质谱法记录质子化三聚氰胺分子（m/z 127）的二级质谱图中的特征碎片（即m/z 110、85和60），可快速检测各种奶制品中的痕量三聚氰胺。质子化三聚氰胺最丰富的离子碎片（m/z 85）的信号响应与奶制品中三聚氰胺的含量具有良好的相关性，动态范围约为5个数量级。对于沉积在纸表面的纯三聚氰胺的检测，检测限（LOD）为3.4×10⁻¹⁵ g/mm²（S/N = 3），这远低于奶粉（1.6×10⁻¹¹ g/mm²，S/N = 3）或液态奶（1.3×10⁻¹² g/mm²，S/N = 3）中三聚氰胺的检测限。检测限的显著差异归因于三聚氰胺与奶制品中蛋白质等基质之间相对较强的分子相互作用。正如使用解吸电喷雾电离（DESI）检测三聚氰胺所证明的那样，削弱分析物与蛋白质之间的分子相互作用被认为是提高常压质谱直接检测蛋白质基质中结合分析物灵敏度的通用策略。该方法用于奶制品中三聚氰胺检测的相对标准偏差（RSD）和回收率分别为5.2%至11.9%和87%至113%。单个样品分析可在几秒钟内完成，为快速筛查奶制品中三聚氰胺的存在提供了一种特别便捷的方法。
