SCF has been used since the late 1970s for the large-scale decaffeination of coffee and tea and the extraction of flavors from hops and other natural sources. But Dupont's recent announcement that it will construct a $40 million pilot plant to explore the commercial feasibility of Teflon manufacture in supercritical CO₂ reflects a growing awareness of the technology's broader applicability.

Supercritical fluids are gases that have been heated above their critical temperature and compressed. The resulting fluid, which is not a true liquid, has a dissolving power that is pressure-dependent. This property can be used for the extraction, fractionation, or purification of complex chemical mixtures based on the differential solubility of their components.

Environmental friendliness is a major driver in SCF, but Phasex has always had a different emphasis, says Mr. Krukonis. Rather than sell SCF for what it doesn't do, Phasex sells SCF for what it can do- especially to improve an existing product or produce a product that cannot be achieved by any other technology.

One example he offers is the formation of nanoparticles of the anticancer agent paclitaxel. Extracted from the yew tree, it must be administered intravenously in a hospital setting due its large particle size.

Precipitation from SCF, however, allows for the careful control of particle size to yield uniform nanoparticles that can be injected intramuscularly at a doctor's office.

The same principle can be applied to many other drugs, and Phasex is working with a Montreal company, RTP Pharma, on the production of nanoparticles of hydrophobic drugs.

Another example is the purification of a polymer used in a medical device. The polymer had an impurity deleterious to the body.

"Using SCF, we process tens of thousands of pounds of this polymer to remove the impurity, which is present at only one-tenth of one percent of the total weight," says Mr. Krukonis.

Phasex has also used SCF for many other applications that benefit from selective extraction, fractionation, ultra-fine particle formation or surface modification. It is even possible to run reactions in SCF.