Sterility is required for medical devices use in invasive medical procedures, and for some situations in the food industry. Sterilization of heatsensitive or porous materials or devices, such as endoscopes, porous implants, liquid foodstuff, and liquid medicine, poses a challenge to current technologies. There has been a steady interest in using high-pressure carbon dioxide as a process medium for new sterilization technology. Among the potential advantages are that CO 2 may sterilize at low temperatures. This paper is a review of the technical and patent literature, including analysis of the microorganisms studied, important operating parameters, and deactivation mechanisms. The current research status and challenges are summarized at the end of this paper.
The superoxide ion (O 2 •-) has been generated electrochemically from oxygen dissolved in two different solvent systems: (1) acetonitrile with tetraethylammonium perchlorate (TEAP) as the supporting electrolyte at elevated pressure and (2) in a room-temperature ionic liquid, 1-n-butyl-3-methylimidazolium hexafluorophosphate ([bmim][HFP]), at atmospheric pressure. A highpressure electrochemical cell with a quasi reference electrode was developed for elevated pressure tests. Increasing the partial pressure of oxygen in the first system increased the rate of superoxide generation because of the increased solubility of oxygen according to Henry's law. The subsequent addition of gaseous carbon dioxide enhances the rate of oxygen reduction in both systems but inhibits the reverse (oxidation) reaction of O 2 •to O 2 . This later observation is consistent with the irreversible formation of a peroxydicarbonate ion, as has been postulated by others.
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