Investigating the Water State in Saccharide Solutions by Infrared/Far-Infrared Spectra in the 1000–100 cm–1 Region Combined with Bands in the 4000–3000 cm–1 Region

TL;DR

This study uses infrared and far-infrared spectra to explore how saccharides affect the structure of water molecules in solution.

Contribution

The study introduces new spectral indices to analyze water structure changes in saccharide solutions using IR and IR/FIR spectra.

Findings

The ratio indices Ahigh/Alow and A3210/A3374 increased with saccharide concentration, indicating stronger water structures.

Saccharide molecules were found to strengthen the hydrogen-bonding network in water.

Differences in water state were observed between IR and IR/FIR spectra, suggesting complementary use of both methods.

Abstract

Water molecules are arranged as tetrahedral structures,
owing to
the hydrogen-bonding network in solution. However, many aspects of
their actual state remain unclear. This study analyzed saccharide
solutions of various concentrations by infrared/far-infrared (IR/FIR)
spectra in the 1000–100 cm–1 region and IR
spectra in the 4000–3000 cm–1 region. The
relationship between the second-derivative intensities of bands at
3210 and 3374 cm–1 attributed to strong and weak
hydrogen bonds, for glucose, maltose, sucrose, and NaCl solutions
at different concentrations, was described by the same straight line.
Two bands were also extracted from the IR/FIR region, which are attributed
to the ordered and distorted structures of the water. The ratio indices
Ahigh/Alow and A3210/A3374 were developed using the intensities of the bands at 673 and 403
cm–1 and at 3210 and 3374 cm–1, respectively. Both indices increased with the saccharide concentration.
The results show that saccharide molecules contributed to the strengthening
of the water structure. Moreover, the change in Ahigh/Alow was small compared to that in A3210/A3374 at high saccharide concentrations. Therefore, a difference in the
state of water possibly exists between those expressed by IR and IR/FIR
spectra, and the complementary use of these spectra is effective
in clarifying the state of water in solution.

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