乙二胺四乙酸二钠的太赫兹及拉曼光谱研究

doi:10.3964/j.issn.1000-0593(2020)09-2707-06

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Abstract Disodium ethylenediaminetetraacetate (EDTA-2Na) is a chelating agent containing carboxyl and amino groups, which has a wide range of coordination properties. EDTA-2Na is often widely added to food as a color protection agent, quality improver and synergistic antioxidant. However, the excessive or improper use of EDTA-2Na will harm human health; even cause temporary blood pressure drop, kidney disorders, etc. Therefore, it is necessary to propose a rapid method of food EDTA-2Na detection. The process of the traditional detection method is complex, time-consuming and labor-consuming. THz time-domain spectroscopy and Raman spectroscopy have good fingerprint characteristics for EDTA-2Na. The advantages of safe and fast detection make it have great application potential. At present, the theoretical and experimental study of EDTA-2Na detection by THz-TDS and Raman spectroscopy has not been reported. EDTA-2Na crystalline powder was detected for the first timer by using THz time domain spectroscopy and Raman spectroscopy. The characteristic absorption and Raman scattering spectra of EDTA-2Na crystal powder in 0.2～2.6 THz band and 10～4 000 cm^-1 band were obtained. Based on density functional theory, the vibration frequency of EDTA-2Na molecule was optimized and calculated by B3LYP/6-31G* group. The corresponding vibration modes were assigned and analyzed. The results showed that there is obvious terahertz vibration absorption at 0.88, 1.40, 1.73 and 2.32 THz for EDTA-2Na, which is basically consistent with the abnormal dispersion frequency of the refractive index spectrum. Moreover, there are obvious Raman characteristic peaks at 921，963，990，1 081，1 336，1 428 and 1 614 cm^-1, which are in good agreement with the experimental results and can be used as the characteristic peaks for identification and detection. In particular, the low-frequency Raman spectrum and THz spectrum in the range of 6.7～85.8 cm^-1 (0.2～2.6 THz) were compared, and the mechanism of characteristic peaks generation was analyzed with density functional theory. The results showed that there is a strong complementarily and consistency between THz spectrum and low-frequency Raman spectrum, which can be used as an effective complementary means of spectrum technology to detect EDTA-2Na, and the results were reliable. The study provides experimental reference and theoretical basis for the detection of food additive EDTA-2Na and the establishment of the database.

Key words：EDTA-2Na; THz spectrum; Raman spectrum; Density functional theory

Received: 2020-02-07 Accepted: 2020-06-02

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https://www.gpxygpfx.com/EN/10.3964/j.issn.1000-0593(2020)09-2707-06 OR https://www.gpxygpfx.com/EN/Y2020/V40/I09/2707