This chapter is part of the series ‘Detection of hydrogen peroxide with Prussian Blue’. In this chapter, we explain what hydrogen peroxide is and why we detect it.
Hyrdogen Peroxide
Most likely hydrogen peroxide (H2O2) is best known for its use in hair bleach. It is the simplest peroxide (a compound with an oxygen-oxygen single bond). It is also a strong oxidizer. Due to its oxidizing properties, hydrogen peroxide is often used as a bleach or cleaning agent. It is used for bleaching hair, fabrics as well as teeth, disinfection of food packaging, medical equipment or to remove fungus. The artificial word “active oxygen” in advertisem*nts for detergents usually indicates hydrogen peroxide mixtures. In many drugstores hydrogen peroxide solutions are available for removing blood stains or similar stains.
The oxidizing capacity of hydrogen peroxide is so strong that it is considered a highly reactive oxygen species. Concentrated hydrogen peroxide, or “high-test peroxide”, is therefore used as a propellant in rocketry.
In fuel cells, hydrogen peroxide is an unwanted side product. To achieve a high energy yield oxygen should be reduced directly to water, consuming four electrons. If the reaction stops at hydrogen peroxide, only two electrons are accepted.
Organisms also produce hydrogen peroxide naturally as a by-product of the oxidative metabolism. A well-known enzymatic reaction is the oxidation of glucose by glucose oxidase. The produced hydrogen peroxide can be used to detect glucose indirectly. Oxidases use the normally present oxygen as an electron acceptor and thus produce hydrogen peroxide after oxidizing their substrate. Consequently, nearly all living things (specifically, all obligate and facultative aerobes) possess enzymes known as catalase peroxidases, which harmlessly and catalytically decompose low concentrations of hydrogen peroxide to water and oxygen.
Accordingly, hydrogen peroxide detection is useful for fuel cell catalyst research, for controlling the number of disinfectants used, for wastewater control and as a basis for a biosensor with a hydrogen peroxide producing enzyme.
Downsides of hydrogen peroxide
Hydrogen peroxide has two disadvantages: Its high oxidative power makes it unstable and corrosive. Because of these characteristics it qualifies as a propellant, but it also can lead to an explosion of highly-concentrated hydrogen peroxide. Additionally, hydrogen peroxide can also damage the skin. Its corrosive influence can be easily identified by white spots on your skin accompanied by a burning or stinging feeling. Washing the skin with a lot of water is advised. After a short period of time, the pain should disappear, but the white spots may remain for a few days. The instability is an issue as well, despite the fact that many hydrogen peroxide solutions have additives to stabilize the peroxide, hydrogen peroxide solutions should be stored cold and dark, otherwise the peroxide might decompose fast. This has the advantage that hydrogen peroxide can easily be removed from any solution by boiling it for several minutes.
