Surfactant-Free Microemulsions in Fragrance Tinctures PERICA BOŠKOVIĆ, VESNA SOKOL, MATEA DUJMOVIĆ, MARTINA GUDELJ, and ANTE PRKIĆ, Faculty of Science, Ruđera Boškovića 33, Split 21000, Croatia (P.B., M.G.), Facult y of Chemistry and Technology, Ruđera Boškovića 33, Split 21000, Croatia (V.S., M.D., A., P.) Accepted for publication February 11, 2021. Synopsis Tinctures are alcoholi c or hydroalcoholic solutions prepared from vegetable or chemical substances. The concentration of the solute varies up to a maximum of 50%, e.g., vanilla tincture. Tinctures are very useful in the perfume industry because they contain ethanol, which can dissolve molecules such as fragrant molecules, and consequently form hydroalcoholic formulations together. Recently, we have shown that nanostructures exist in the monophasic water–ethanol–citronellol system, and it is therefore a question whether such nanostructures exist in a system where a perfume molecule of citral is present as the oil component instead of citronellol. In this study, the single-phase region was mapped conductometrically and then measured by Dynamic Light Scattering (DLS) and UV/Vis spectroscopy to determine the presence of nanostructures similar to classical microemulsions. In early 1970s, Barden ’ s group began working on microemulsions without the presence of a surfactant. They were the fi rst to characterize such solutions with many methods and experiments (1). Later, microemulsions without the presence of a surfactant become a signifi cant medium for various enzyme-catalyzed reactions as well as other chemical reac- tions. For example, Zoumpanioti et al. (2) studied the catalytic activity of lipases trapped in ternary systems without surfactants, consisting of water, short-chain alcohol, and hex- ane. Both enzymes effectively catalyze the esterifi cation of acids. The authors have shown that the stability of encapsulated enzymes at low water contents in the system is higher than that found in microemulsions with classical surfactants. We have recently shown that nanostructures exist in microemulsions without surfactants based on fragrance tinctures, composed of monophasic water–ethanol–citronellol mixtures (3). Consequently, the question of the existence of such nanostructures in other perfume tinctures arises. To answer that question, we have formulated tinctures with citral mole- cules that are structurally very similar to citronellol molecules. In recent years, stati c and dynamic percolation models for describing the microstructure of microemulsions have become very common. In the static percolation theory, the result Address all correspondence to Perica Bošković at pboskovic@pmfst.hr. J. Cosmet. Sci., 72, (May/June 2021) 292–297 292