Hydrogen peroxide (H202) is a familiar household antiseptic. It was discovered in 1818 and was early recognized as possessing antibacterial properties. These were extensively investigated in 1893 by Traugott. Hydrogen peroxide is available as a solution designated as 20- or 10-volume, a means of indicating its strength by describing the volume (20 or 10, respectively) of oxygen evolved from 1 volume of the peroxide solution. Strengths for industrial use of 35, 50 or 90% are available. Hydrogen peroxide solutions are unstable, and benzoic acid or another suitable substance is added as a stabilizer.
Hydrogen peroxide solutions possess disinfectant, antiseptic and deodorant properties. When in contact with living tissue and many metals they decompose, evolving oxygen. Hydrogen peroxide its bactericidal and sporicidal (Russell, 1982, 1990a,b, 1991a,b; Baldry, 1983; Baldry & Fraser, 1988). It is believed to act as a generator of free hy-droxyl radicals, which can cause DNA strand breakage in growing bacteria but the mechanism of action of hydrogen peroxide on spores is not the same. The current hypothesis is that hydrogen peroxide treatment results in spores which cannot swell properly during spore germination (Melly et al., 2002). It is an oxidizing agent and reacts with oxidizable material, for example alkali nitrites used in anticorrosion solutions. It is environmentally friendly because its decomposition products are oxygen and water (Miller, 1996) and has been investigated as a potential sanitizing agent in the food industry (Shin et al., 2001; Melly etal, 2002).
Hydrogen peroxide has been used in aseptic packaging technology and also for disinfecting contact lenses as it has been shown to be effective against the opportunistic pathogen Acanth-ameoba, the causative agent of Acanthameoba keratitis. This is a potentially blinding infection which contact lens users are more susceptible to (Hughes & Kilvington, 2001). The use of hydrogen peroxide as a contact-lens disinfectant has been reviewed (Miller, 1996) and is further described in Chapter 8.1.
Microbial inactivation is more rapid with liquid peroxide than with vapour generated from that liquid acting at the same temperature (Sintim-Damoa, 1993). However, the vapour can be used for the purposes of sterilization, where, at a concentration of 1-5 mg/L, it generally shows good penetration.
Attention has recently been devoted to developing a plasma-activated peroxide vapour process, in which radio waves produce the plasma. This is believed to be microbicidal by virtue of the hydroxyl ions and other free radicals that are generated (Groschel, 1995; Lever & Sutton, 1996).
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