In Situ Water Quantification in Natural Deep Eutectic Solvents Using Portable Raman Spectroscopy

Area of Science:

• Analytical Chemistry
• Green Chemistry
• Spectroscopy

Background:

• Natural Deep Eutectic Solvents (NADES) are sustainable alternatives to traditional organic solvents.
• Water content critically impacts NADES properties and applications.
• Portable Raman devices offer convenient, on-site analysis but require performance validation.

Purpose of the Study:

• To compare the performance of a portable Raman system against a research-grade microscope for water content determination in NADES.
• To evaluate the feasibility of in-situ, through-glass quantification of water in NADES using portable Raman spectroscopy.
• To assess the accuracy and reliability of portable Raman for NADES analysis in laboratory and industrial settings.

Main Methods:

• Analysis of three NADES systems (Betaine Glycerol, Choline Chloride Glycerol, Glucose Glycerol) with varying water content (0-28.5%).
• Utilized portable Raman spectroscopy coupled with Partial Least Squares Regression (PLSR) for quantification.
• Direct comparison of results with data obtained from a research-grade Raman confocal microscope.

Main Results:

• PLSR models demonstrated high reliability with R² values exceeding 0.99 for all NADES systems.
• Portable Raman achieved prediction errors (RMSEP) below 5% for water content determination.
• Accurate quantification of water content was achieved directly through glass vials, without sample removal.

Conclusions:

• Portable Raman spectroscopy is a reliable and accurate tool for in-situ water content determination in NADES.
• The method eliminates the need for sample preparation, solvents, and consumables, supporting green chemistry principles.
• Portable Raman offers a promising solution for high-throughput monitoring and quality control of NADES in research and industry.