Abstract
Natural Deep Eutectic solvents (NADES) are green, ionic solutions prepared by mixing vegetal cellular constituents. They are renewable and biodegradable solvents composed of hydrogen bonded donor and acceptor compounds. NADES have a wide range of applications, mainly as solvents for extraction of plants, biocatalysis, and nanoparticle synthesis. Water content is very critical, impacting significantly on NADES properties. Therefore, controlling H2O concentration appears essential for optimal use of NADES. In the present study, Attenuated Total Reflectance - infrared spectroscopy (ATR-IR) coupled to multivariate analysis, namely Partial Least Square s regression (PLSR), was investigated as a rapid, label free and cost-effective tool for measuring the water concentration of NADES. Betaine_Glycerol (BG), Choline Chloride_Glycerol (CCG) and Glucose_Glycerol (GG) were the selected model systems, each over a range of concentrations between 0% (w/w) and 40% (w/w). PLSR results demonstrate the robustness of the analysis, yielding R-2 values of 0.99 and Root Mean Square Error of Cross Validation (RMSECV) of respectively 02602% w/w, 0.6883% w/w and 0.7034% w/w. Moreover, the % relative error achieved is below a 5% threshold, further highlighting the suitability of ATR-IR for water content monitoring. This preliminary work demonstrates the appropriateness of developing easily accessible analytical tools to support the development of green chemistry solvents, which currently represent a major focus of interest in both research and industrial environments. (C) 2020 Elsevier B.V. All rights reserved.