三聚氰胺和三聚氰酸的太赫兹光谱研究

Terahertz Spectroscopic Study on Melamine and Cyanuric Acid

[目的]用太赫兹时域光谱技术(THz-TDS)研究三聚氰胺的波谱特征,以鉴别乳品中是否添加三聚氰胺。[方法]采用THz-TDS技术测量了室温下三聚氰胺和三聚氰酸在0.3～2.5 THz的吸收谱和折射率谱。[结果]2种样品在0.3～2.5 THz波段各有明显的特征吸收峰,三聚氰胺在1.98和2.24 THz,三聚氰酸在1.27和2.37 THz,这是用THz-TDS技术进行鉴别的基础。密度泛函理论计算和晶体数据表明,2种样品的THz吸收光谱主要来源于分子间的与氢键相关的集体振动模式。三聚氰胺在该波段的吸收谱,可用于奶粉中不同含量三聚氰胺的定量分析,也可用于研究三聚氰胺和三聚氰酸形成的1∶1网状结构。[结论]太赫兹光谱不仅是鉴别三聚氰胺与三聚氰酸的有效手段,而且为研究它们之间的复合物结构提供了新的思路。

[ Objective ] Spectroscopic character of melamine was investigated with Terahertz time-domain spectroscopy in order to identify melamine in dairy. [ Method]The spectra of absorption and refractive index of melamine and cyanuric acid at 0.3 - 2.5 THz were measured in room temperature by using THz-TDS technology. [ Result ] The each of two samples had obvious characteristic absorption peak at wave band of 0.3 -2.5 THz, the melamine had absorption peaks at 1.98 and 2.24 THz and cyanuric acid at 1.27 and 2.37 THz, which was the foundation for identification with THz-TDS technology. The Density Functional Theory （DF＇I＇） calculation and crystal data showed, the THz absorption spectra of 2 samples were mainly come from collective vibration modes related with hydrogen bonds between molecules. The absorption spectrum of melamine at this wave band could be used for quantitative analysis of melamine with different contents in milk powder, and also could be used for study on 1：1 reticular structure formed by melamine and cyanuric acid. [ Conclusion] THz-TDS was not only the effective means of identification of melamine and cyanuric acid,but also supplied a new thought for research of the complex structure between them.