Terahertz and infrared characteristic absorption spectra of aqueous glucose and fructose solutions

Chao Song,Ling Ding,Ze-You Chen,Wen-Hui Fan,Kai Wang,Xu Chen

doi:10.1038/s41598-018-27310-7

Abstract

In this paper, the terahertz (THz) and infrared (IR) characteristic absorption spectra of aqueous glucose solutions and aqueous fructose solutions with different concentrations were measured and studied. The absorption spectra of these two molecules in solid-state and in aqueous solutions were compared and analyzed, the significant effect of molecular adjacent environment on the molecular structure and vibrational mode was revealed. In addition, the THz and IR absorption spectra of these two isomers’ aqueous solutions were also compared and explored. No obvious differences were found from their IR absorption features measured at room temperature, while their THz absorption spectra do have the differences, indicating THz characteristic absorption spectra more suitable for the detection and identification of aqueous glucose and fructose solutions. The results are helpful to understand the influence of aqueous solutions environment on the molecular structures and vibrational modes of the materials, and also provide a theoretical reference for the quantum chemical calculation of biological macromolecules.

Highlights

As the important biological molecules consisting of carbon (C) atom, hydrogen (H) atom and oxygen (O) atom, saccharides normally can be classified as four chemical groups: monosaccharides, disaccharides, oligosaccharides, and polysaccharides
In the practical applications, the main functions of biomolecules are realized in aqueous solutions rather than in solid-state environment, some researchers have achieved some advancements in characterization and quantification of glucose or fructose contents in fruits and biomedical applications[9,10,11,12], the direct identification of aqueous glucose solutions and aqueous fructose solutions by using THz time-domain spectroscopy (THz-TDS) was studied much less due to the strong water absorption
The absorption of both aqueous glucose solutions and aqueous fructose solutions is stronger, and the absorption intensities increase with the concentrations increasing, indicating clearly the THz absorption spectra of aqueous glucose solutions and aqueous fructose solutions affected by the amount of glucose or fructose molecules involved

Summary

Introduction

As the important biological molecules consisting of carbon (C) atom, hydrogen (H) atom and oxygen (O) atom, saccharides normally can be classified as four chemical groups: monosaccharides, disaccharides, oligosaccharides, and polysaccharides. Glucose and fructose are two kinds of monosaccharides required in human daily life Both of them are white crystals at room temperature and have been used widely in the food industry. There are four glucose molecules in the unit cell of glucose and four fructose molecules in the unit cell of fructose, respectively They have different symmetry, which affect the number of infrared (IR) vibrational mode and the characteristic absorption spectra in terahertz (THz) region. As the THz spectra is quite sensitive to the difference in organic molecular structure and their surrounding environment[4,14,15], THz time-domain spectroscopy (THz-TDS) can be used as a new non-destructive detection technique to realize rapid and effective detection as well as qualitative identification of materials[16,17,18,19,20]. The combination of FTIR and THz-TDS technology is valuable in studying the characteristic absorption spectra of materials, which can effectively achieve technical complementarities and improve the characteristic absorption spectra information on the corresponding materials

Methods

Results

Conclusion