Partitioning behavior of rutin in novel liquid–liquid biphasic systems formed by choline chloride/ maltose natural deep eutectic solvents and n-propanol

The development of promising environmentally friendly extraction tools has been one of the hottest topics in green chemistry. Among these, natural deep eutectic solvents (NADESs) as green extraction media have received widespread recognition. In this paper, with the aim of exploring the potential applications of NADESs in the extraction field, water-soluble n -propanol was used to form liquid–liquid biphasic systems with choline chloride/ maltose NADESs. The phase behavior of those systems was designed by adjusting the molar proportion of the hydrogen bond acceptors (HBA): hydrogen bond donors (HBD) and temperature. This allows for the systems tailored to the specific requirements of the target molecule, as shown by their application in the extraction of rutin. Investigation of the distribution behavior of rutin suggested that the partition coefficient and the extraction efficiency of rutin in the bottom phase increase significantly with decreasing temperature and increasing HBA : HBD molar ratio. And with the temperature of 288.15 K, the highest TLL of NADES (ChCl: Mal = 1:2) + NPA + water system achieved higher E% of 94.27 %. The interaction force between NADES and rutin was studied using the Hansen solubility parameter, it turned out that Δ δ i , j $\mathrm{\Delta }{\delta }_{i,j}$ of the 2:1 and 1:2 M ratio of NADES was only 8.91, 5.12, which meaning that there may be strong interactions between NADES and rutin. In addition, the hydrogen bond ( Δ δ H $\mathrm{\Delta }{\delta }_H$ ) of the NADES (HBA: HBD = 1:2) was 25.47, which is greater than other interaction force, revealing that the hydrogen bond is the maximum force between rutin and the NADES (HBA: HBD = 1:2). The energy ( Δ G T $\mathrm{\Delta }{G}_T$ ), enthalpy ( Δ H T $\mathrm{\Delta }{H}_T$ ) and entropy ( Δ S T $\mathrm{\Delta }{S}_T$ ) calculated from the partition data of rutin was consistent with the free energy ( Δ G C ) $(\mathrm{\Delta }{G}_C)$ , enthalpy ( Δ H C ) $(\mathrm{\Delta }{H}_C)$ and entropy ( Δ S C ) $(\mathrm{\Delta }{S}_C)$ changes of system, which confirmed that the driving force of the phase separation of the system drives the transfer of rutin to the lower phase. In addition, we used eco-friendly water to regenerate NADES. The recovery efficiency of rutin was explored while NADES was reused in three cycles. This result showed there was no change observed in the extraction capability for rutin in those system. Finally, a larger aggregate of size 1315 nm was observed by dynamic light scattering, which furthermore demonstrated that the hydrogen bonding interaction between NADES (HBA: HBD = 1:2) and rutin is the main driving force tool for enhancing rutin partitioning. This method presents a newly system constructed by NADES and NPA for the green extraction, revealing the feasibility of the system for rutin extraction and facilitating industrial applications.