Essential oil components as GC-compatible hydrophobic deep eutectic solvents to extract regulated compounds from water-based fragrances

Objective Essential oils (EOs) are an excellent source of compounds that can be used in several fields. They belong to different chemical classes (mono- and sesquiterpenes and terpenoids, phenols, ...) and are generally hydrophobic. Therefore, they are optimal candidates for the preparation of hydrophobic natural deep eutectic solvents (NADES), i.e. solvents formed by a combination of a hydrogen bond acceptor (HBA) and a hydrogen bond donor (HBD) with a lower melting point than one of the two components and characterized by low toxicity and envıronmental ımpact, ease of preparation, wide range of applications and low raw material costs. They have been widely applied as extraction phases [1] but few studies report the combination of NADES-based extraction and gas chromatographic analysis [2]. Indeed, GC analysis of regulated substances and possible cross-contamination in perfumes is the approach of choice in fragrance quality control laboratories. Conventional analytical methods require either large amounts of organic solvents or a direct injection of samples, which imply possible interferences and/or frequent maintenance of the chromatographic system, especially for fragrances with high water content. This research work aims to develop a more environmentally friendly NADES based approach using essential oil components to extract and enrich volatile compounds from water-based perfumes. Methods Thymol, eugenol, 1,8-cineole, and nootkatone isolated from different EOs and mixed in the appropriate molar ratio were used to prepare NADES. The NADES were dispersed in water-based fragrances by dispersive liquid-liquid microextraction (DLLME) to isolate a set of suspected allergens and cross-contaminants. Thanks to the volatile nature of the adopted terpenoids and phenolic compounds, the enriched NADES were directly analyzed by GC-FID and GCMS. Results After optimization of the NADES composition and extraction conditions, the investigated EO component-based solvents were succesfully applied to recover the target volatile components from water-based perfumes with good figures of merits (accuracy, precision, enrichment factor, recovery, linearity). Direct analysis of the enriched NADES is possible not only via GC-FID but also via GC-MS. The solvent components must be chosen to avoid interference with the elution of the target analytes since MS acquisition has to be interrupted during HBA and HBD elution. Conclusions Natural resources have recently become very important in terms of sustainable growth and development. This study shows that EOs are a valuable source of phytochemicals that can also be used to generate green solvents for several applications, including analytical scale extraction.