The identification and quantification of free fatty acids (FFA) in edible and non-edible vegetable oils, including waste cooking oils, is a crucial index to assess their quality and drives their use in different application fields. NMR spectroscopy represents an alternative tool to conventional methods for the determination of FFA content, providing us with interesting advantages. Here the approaches reported in the literature based on ¹H, ¹³C and ³¹P NMR are illustrated and compared, highlighting the pros and cons of the suggested strategies.

The consideration towards waste cooking oils is changing from hazardous waste to valuable raw material for industrial application. During the last 5 years, some innovative processes based on the employment of recycled waste cooking oil have appeared in the literature. In this review article, the most recent and innovative applications of recycled waste cooking oil are reported and discussed. These include the production of bioplasticizers, the application of chemicals derived from waste cooking oils as energy vectors and the use of waste cooking oils as a solvent for pollutant agents.

Unlike the archetypal deep eutectic solvent (DES) choline chloride:urea (ChCl:U), fundamental knowledge of the intermolecular network in choline acetate (ChOAc) DESs and how they change upon dilution is still missing. Here we jointly use UV resonance Raman (UVRR) and NMR spectroscopy to comparatively explore how the strength and distribution of hydrogen bonding and the solvation of the components are modified in ChOAc:U and ChCl:U with increasing hydration. Overall, Raman and NMR data indicate that ChOAc:U is continuously affected by hydration and, even at low water concentrations, undergoes a breakage of DES–DES interactions, with rapid solvation of the urea portion and full exchange of mobile protons. On the contrary, ChCl:U seems to maintain its structure as small interplays gradually occur between urea in the DES and the surrounding water molecules. The combined approach provides a multifaceted consistent description of the systems, outlining the crucial role of the anion in driving the structure and dynamics of the materials and then yielding valuable data toward the exploitation of DESs as tunable systems.

The Deep Eutectic Solvents (DESs) choline chloride:urea (x_ChCl= 0.33) and choline chloride:glycolic acid (x_ChCl= 0.5) were studied using viscosity-corrected³⁵Cl NMR and MD simulations to probe the role of chloride as a function of water content.