THz properties of two food additives sodium solution based on microfluidic chips

Abstract

The vibration and rotation energy levels of many molecules are in the terahertz (THz) band, so THz spectroscopy can be used to qualitatively identify substances. However, the terahertz spectrum of most molecules in aqueous solution is completely different from that of solid molecules, and they have strong absorption characteristics for terahertz waves. Therefore, how to reduce the absorption of water for THz wave has become an urgent problem to be solved. Food additives are our daily necessities. They can extend the shelf life of food. In this study, a microfluidic chip with very low THz wave absorption was designed, and the THz transmission spectra of food-additive sodium hexametaphosphate solution and sodium pyrophosphate solution were measured using THz time domain spectroscopy (THz-TDS) system. The experimental results show that the THz spectral intensity of the two sodium salt solutions increases with the increase of solution concentration, which is completely contrary to the phenomenon of common sodium salts, such as sodium chloride. It shows that the process of ion hydration affects the hydrogen bond between water molecules and changes the absorption of THz waves by water. This method lays a foundation for further study of the THz characteristics of electrolyte solutions.