Abstract
Vibrational coupling between carbohydrates and the hydration shell is unveiled as the underlying mechanism that improves wavenumber-selectively the carbohydrate discrimination performance by near-infrared (NIR) spectroscopy. The investigation is based on measurement of six carbohydrates (fructose, glucose, mannose, ribose, xylose and sorbitol) in aqueous solution in different concentration levels (5 mg/L, ~0.03 mmol/dm-3 and 20 mg/L, ~0.1 mmol/dm-3). The results of multivariate classification are interpreted by quantum mechanical NIR spectra simulations. The simulation unveils that the phenomenon is vibration-selective and thus wavenumber-selective, and leads to an enhancement of the qualitative information contained in the specific spectral regions. The location of these regions and the related performance correspond fully to the appearance and magnitude of the unveiled cooperative vibration effect.
Highlights
The coherent nature of vibrational modes of water is an intensively studied topic [1,2]
Due to the complete absorption of the incident NIR light by the combination band of water centered at 5200 cm−1, obvious artifacts occurred in that region. This can be avoided by utilizing cells with a lower pathlength [34,40,41], previous studies have demonstrated the great suitability of a 1 mm cell pathlength for aqueous carbohydrate systems [17,42,43]
This is further illustrated by a magnification of the two wavenumber regions of interest shown in Fig. 2b and Fig. 2c
Summary
The coherent nature of vibrational modes of water is an intensively studied topic [1,2]. Based on non-linear IR spectroscopy investigations and theoretical calculations, it has been evidenced that the intermolecular vibrational coupling between water molecules acts as a perturbation delocalized over a volume [3,4,5]. A recent investigation suggested that this phenomenon may enhance the sensitivity of spectroscopic analyses, and proposed that the interaction between a target molecule and its first hydration shell is further propagated through consecutive hydration shells. This interaction and propagation acts as a perturbation that effectively increases the amount of molecular oscillators sensed in a spectroscopic measurement [7]. The influence of the vibrational coupling occurring in the analyte-hydration shell system on analytical spectroscopy has not been fully understood
Sign-in/Register to view highlights & summary Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callMore From: Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy
Disclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
