Vapour pressure of a fragrance ingredient during evaporation in a simple emulsion S.E. FRIBERG*, M. SZYMULA, L. FEI, J. BARBER and A. AL-BAWAB Center for Advanced Materials Processing, Clarkson University, Potsdam, NY 13699-5814, USA P.A. AIKENS ICI Surfactants, Concord Plaza, Bedford Bldg, 3411 Silverside Road, Wilmington, DE 19850-5391, USA Received 14 April 1997 Accepted 30 July 1997 Keywords: fragrances; emulsions; evaporation; phase equilibria; liquid crystals; detergents; association structures Synopsis The phase diagram water, phenethyl alcohol and laureth 4 was determined and the variation of the vapour pressure of the alcohol was determined during evaporation using gas chromatographic head-space analysis. The phase changes during evaporation were estimated from the phase diagram and compared to the appearance of the emulsion using optical microscopy. The transfer of the fragrance ingredient between different phases during the process was estimated and its measured vapour pressures compared to those calculated from values of earlier determination in different phases in the system. The agreement was good. R´ esum´ e On a ´ elabor´ e le diagramme de phase eau, alcool ph´ en´ ethylique et laureth 4 et on a d´ etermin´ e la variation de la tension de vapeur de l’alcool durant l’´ evaporation en utilisant l’analyse par chromatographie gazeuse ` a injection directe en tˆ ete de colonne. Les changements de phase durant l’´ evaporation sont estim´ es ` a partir du diagramme de phase et compar´ es ` a l’aspect de l’´ emulsion par microscopie optique. On a estim´ e le transfert de l’ingr´ edient parfum´ e entre les diff´ erentes phases durant le processus et ses tensions de vapeur mesur´ ees ont ´ et´ e compar´ ees ` a celles calcul´ ees ` a partir de valeurs d´ etermin´ ees ant´ erieurement dans diff´ erentes phases du syst` eme. La concordance est satisfaisante. Introduction Fragrances are an essential part of personal-care formulations – especially skin lotions – and it is well known that fragrance perception is a decisive element in consumers’ selection of products. With this in mind, the evaluation of fragrance materials has developed into a highly sophisticated art executed by highly trained and skilful persons with a vast knowledge of useful combinations of different compounds. The analysis of fragrance combinations has taken a large step forward with the application of the gas chromatography/mass spectrometer combination, and the literature in this field is now vast, providing exact information about the composition of natural *To whom correspondence should be addressed. 0142–5463 © 1997 International Journal of Cosmetic Science International Journal of Cosmetic Science 19, 259–270 (1997)