Molecular detection of sodium nitrate and sodium nitrite based on THz-TDS system

摘要

Terahertz spectroscopic characteristics are related to the large amplitude vibration of molecules and their interaction, soit can be used for molecular detection. Sodium nitrate and sodium nitrite are two very important salts in people's lives.Sodium nitrate is usually used as quick-acting fertilizer in acidic soil, but excessive use will cause certain pollution to theenvironment. If sodium nitrate is heated, it becomes very stable sodium nitrite, which is usually added to food as apreservative and colorant, but excessive consumption of nitrite can lead to food poisoning and even death. Therefore, itis necessary to detect sodium nitrate and sodium nitrite. Based on THz-TDS system, the spectral characteristics ofsodium nitrate and sodium nitrite in 0.1-1 THz band were studied. Polyethylene, sodium nitrate and sodium nitrite weremixed in proportion of 1:1, 1:2, 1:3, 1:4 and 1:5, respectively. The mixture was evenly grinded and stirred, and thenpressed. The prepared samples were tested in THz-TDS system, and the time-domain spectra of the samples withdifferent proportions were obtained. The terahertz frequency spectrum and absorption spectra of the two samples atdifferent ratios were obtained by Fourier transform. After comparing spectra of the two samples, it is found that theyhave their own absorption peaks, and their peak positions are obviously different. Therefore, it is very important to studythese two substances by terahertz technology.