Vibrational coupling to hydration shell - Mechanism to performance enhancement of qualitative analysis in NIR spectroscopy of carbohydrates in aqueous environment

摘要

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, similar to 0.03 mmol/dm(-3) and 20 mg/L, similar to 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. (C) 2020 The Authors. Published by Elsevier B.V.