## 3 Results and Discussion
### Physicochemical Properties  
#### 3.1.1 FTIR Analysis  
In the case of NADES, it is critical to investigate the strength of hydrogen bond interactions between HBD and HBA. FTIR spectrometry is one of the widely used methods for analyzing the interaction of different groups and identifying the structure of a material [33; 34]. Due to its sensitivity to the change of microstructure [35], FTIR is suitable for characterizing the hydrogen bond interactions. The FTIR spectra were recorded for HBD, HBA, and NADES1 (LA:ChCl), NADES2 (LA:SL), and NADES3 (LA:GL:W), and NADES diluted with 10-40% water (Figures S1-S3). The FTIR spectra of lactic acid, choline chloride, sorbitol, and glucose (Figures S1-S3) agree with those reported in the literature [36; 37; 38; 39]. According to the FTIR spectra (Figures S1-S3), it is evident that the NADES spectra overlap the spectra of respective HBA and HBD with slight differences. In the spectra of all NADESs, peak broadening and shifting are observed. The most pronounced differences are observed in the region corresponding to the stretching vibrations of the O-H bond (3200-3600 cm\({}^{-1}\)). A peak around 1730 cm\({}^{-1}\) is ascribed as C=O stretching vibrations, while the signals in the 1000-1300 cm\({}^{-1}\) region can be related to C-O, C-C-O, and C-O-C stretching vibrations, and C-O-H bending vibrations. The shift and the broadening of the peaks indicate the formation of hydrogen bonds between molecules, which confirms intermolecular bonding between components. Regarding NADES1 (Figure S1), the shift of O-H stretching in FTIR spectra was observed after the formation of the NADES to higher wavenumber (3323 cm\({}^{-1}\)). The hydroxyl groups of lactic acid were attracted to chlorine anion in choline chloride, consequently producing an O-H-Cl bond. It was also observed that the C=O bond and C-O stretching shifted to the lower wavenumber with increasing the ratio of water in the NADES. The FTIR spectral analysis of NADES2 revealed several deviations from the spectra of the individual components (Figure S2). The broadening of all signals in the NADES spectra suggests a more complex hydrogen-bonding network within the NADES, as multiple functional groups from both components interact more extensively. Originally, a characteristic peak for lactic acid at 1727 cm\({}^{-1}\) was associated with C=O stretching vibrations. The decrease in intensity suggests a possible interaction or reaction involving the carboxylic group, potentially through hydrogen bonding with hydroxyl groups of sorbitol. Additionally, a deviation in the signal at 1217 cm\({}^{-1}\) is typically noted in lactic acid spectra for C-O stretching. It indicates altered molecular environments, likely due to interactions with sorbitol. This shift not only supports the presence of altered bonding but also may influence the reaction dynamics and solvation capabilities of the NADES. The peak at 1122 cm\({}^{-1}\), typically a sharp feature due to lactic acid's C-O stretching, shows a notable decrease in intensity. This alteration suggests a modification potentially influenced by the interaction with sorbitol. In the FTIR spectra of NADES3 (Figure S3), several deviations from the spectra of individual components were also observed. A new peak at 1650 cm\({}^{-1}\) likely represents the formation of complex intermolecular hydrogen bonds between the hydroxyl groups of lactic acid and the anomeric center of glucose. The broadening signal at 1028 cm\({}^{-1}\) could reflect a change in the environment around the C-O stretching vibrations in glucose and the C-OH groups in lactic acid. It will be possible due to the formation of a more complex hydrogen-bonding network. Peak disappearance at 838 cm\({}^{-1}\) and 612 cm\({}^{-1}\) on glucose FTIR spectra typically associated with specific vibrational modes of glucose suggests significant alterations in its structural conformation or interactions that prevent these vibrations within the NADES matrix. The impact of water addition on the stability of hydrogen bonds in NADESs was examined.