72 JOURNAL OF COSMETIC SCIENCE SUPERCRITICAL FLUIDS: INNOVATIONS IN MATERIALS PROCESSING Anthony M. Gudinas • and Yelena Zolotarsky 2 •Phasex Corporation and 2 Lavipharm Labs Supercritical fluids (SCFs) are currently being applied in diverse industry segments and areas of research. The increasing applications have been driven by tighter restrictions on solvent use worldwide and the benefits delivered by processing with SCFs. They have been used for more than twenty years for processing of coffee, tea, spices, hops, and other foods to produce improved and solvent free products. The use of these high pressure gases, especially carbon dioxide, as extraction solvents was put into industrial use in the late 1970s, first in Germany where restrictions on certain organic solvents used in coffee decaffeination forced manufacturers to seek alternatives. The combination of technical success and the proliferating knowledge of operating large industrial processes have proved that processing with SCFs is a viable and scaleable industrial process. Supercritical fluids are defined by a unique temperature and pressure above which they cannot be liquefied no matter what the pressure, viz., the critical point. Hannay and Hogarth first reported the phenomenon of SCF solubility over 100 years ago. These researchers found that when the pressure and temperature of ethanol was raised above its critical point, the fluid could dissolve a solid having no measureable vapor pressure, and when the pressure was lowered (but pressure still above the critical point), the solid "precipitated as a snow". Although the findings of Hannay and Hogarth were of significant fundamental interest, it was not until 1955 that Todd and Elgin first suggested that SCFs could represent a useful extraction technique. In their studies of phase equilibria of a number of solutes in supercritical ethylene, Todd and Elgin described a new process for separating mixtures "wherein the nonideality is intentionally created" for effecting separation. They compared the technique to liquid-liquid extraction, describing the concept of selectively dissolving one compound from a mixture under supercritical conditions, and recovering the solute by decompression. The implications of their statements were not fully realized for more than a decade, but today the concept has evolved into a broad discipline of processing technology. Supercritical fluids have an interesting combination of liquid-like and gas-like properties that make them uniquely suited for carrying out a variety of operations. The diffusivity of a solute in a supercritical fluid is one or two orders of magnitude higher than in liquid solvent, which translates to higher extraction rates where the major resistance is at the solid-solvent interface. The viscosity of a supercritical fluid is much lower than that of a liquid, and a low viscosity and additionally no surface tension limitations allows the extraction of materials from pores and cell structures with dimensions much less than one micron. Conversely, materials can be infiltrated and deposited in small pores because of the absence of surface tension. The most important feature of SCFs that is exploited for processing operations is their pressure dependent dissolving characteristics. Unlike liquid solvents whose solubility properties can be manipulated only by temperature changes, SCFs have the additional "tunable" parameter of pressure. As Todd and Elgin had pointed out in 1955, because of such solubility characteristics it is possible to design industrial processes to extract, purify, and fractionate materials based on changes in pressure o• a SCF. SCFs offer advantages over traditional organic solvents for several technical and regulatory reasons. Replacing organic solvents with carbon dioxide, for example, eliminates many FDA, EPA, and OSHA issues. Gases leave no solvent residues and thus provide a cleaner, purer product. Often times, only mild operating temperatures are required allowing heat labile materials to be processed. SCFs have the ability to selectively extract a compound from a substrate and can thus separate and purify in one step. The applications of SCFs have gone beyond the traditional areas of hops extraction and coffee decaffeination to include the pharmaceuticals, polymers, surfactants, intermediate and fine chemicals, nutraceuticals, and cosmetics industries, and most recently supercritical fluids are proliferating in metals degassing and dry cleaning. SCFs are used in the pharmaceuticals area for small particle formation and combining a drug and excipient to form a homogeneous composite material. Polymers such as polyolefins, polysiloxanes, fluoropolymers, and polyols can be fractionated to obtain a certain MW fraction with desired properties or to remove impurities. Actives from botanical substrates can be extracted at higher concentrations and purity, examples are lycopene, astaxanthin, and fish oils for use in nutraceuticals. The cosmetics industry is another area where SCFs can be applied with success. Essential oils and fragrances can be extracted for use as excipients and additives. Surfactants can be purified and the color bodies removed for a more desireable product.

2001 ANNUAL SCIENTIFIC MEETING 73 The presentation will highlight the history of SCFs and how they evolved from a laboratory curiosity to a multimillion pound per year processing technology. A technical description of how SCFs work and can be applied to different processes will be given. Finally, and most relevant for this audience, the applications of SCFs in the cosmetics industry will be presented..