Development of essential oil diffusion matrices using non-ionic surfactants-supported NADES and hydrophobic NADES†

Abstract

Natural deep eutectic solvents (NADES) represent a significant advance in green chemistry, offering an eco-friendly alternative to conventional organic solvents for applications in extraction, reaction media, and formulations. This study explores the application of NADES in essential oil formulations, using lavender essential oil (LEO) to investigate the solubilization and release of volatile organic compounds (VOCs). Two distinct NADES formulations were evaluated: hydrophilic NADES combined with surfactants, and hydrophobic NADES. The results show that hydrophilic NADES, when combined with non-ionic surfactants, form stable emulsions that effectively solubilize and release LEO's VOCs, overcoming the high hydrophilicity limitation of NADES. Headspace analysis and gas chromatography-mass spectrometry (GC-MS) identified 25 VOCs, with differential components analyzed through orthogonal partial least-squares discriminant analysis (OPLS-DA). VOCs were well-clustered in OPLS-DA and principal component analysis (PCA), with five clearly differentiated groups (C, N1, N3, N5, and N9). However, challenges remain, particularly in the solubilization and gradual release of VOCs. In contrast, hydrophobic NADES demonstrated a controlled release mechanism, effectively encapsulating and steadily releasing VOCs, making them advantageous for sustained fragrance delivery. The study further emphasizes the importance of the Hydrophilic–Lipophilic Balance (HLB) in NADES formulations, showing that adjusting HLB through surfactant concentrations significantly influences VOC release dynamics. In conclusion, this research highlights the potential of NADES as efficient, eco-friendly solvent systems for essential oil applications. By providing insights into optimizing NADES compositions for specific solubility and release profiles, the study identifies both challenges and opportunities, paving the way for further advancements in green chemistry.