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

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 THz spectrum of most molecules in aqueous solution is completely different from that of solid molecules, and they have strong absorption characteristics for THz waves. 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). The results show that the THz transmission spectral intensity of the two sodium salt solutions increases with the increase of solution concentration, which is due to the influence of ion hydration process on hydrogen bonds 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.