Sodium perborate (SPB) is a white, crystalline, inorganic chemical compound. It functions primarily as a stable source of active oxygen, making it a powerful oxidizing agent. Its stability in a dry, powdered form allows for easy incorporation into various dry-mix formulations. The compound commonly exists as a hydrate and is leveraged across several industries requiring controlled oxidation.
Chemical Composition and Mechanism of Action
Sodium perborate is a true chemical compound containing a peroxyborate anion. When dissolved in water, this compound undergoes hydrolysis, which breaks it down to release hydrogen peroxide and borate. The hydrogen peroxide is the active component, acting as a bleaching and cleaning agent by releasing “active oxygen.”
The controlled release of hydrogen peroxide offers a solid-form alternative to handling unstable liquid hydrogen peroxide. Sodium perborate is commercially available in two primary forms: the tetrahydrate and the monohydrate. The monohydrate is preferred in modern formulations because it has a higher percentage of available active oxygen and dissolves more quickly in water.
The oxidizing action is relatively slow at lower temperatures, becoming much more rapid above 60 degrees Celsius. For lower-temperature activation, manufacturers often include an additive like tetraacetylethylenediamine (TAED). This activator reacts with the released hydrogen peroxide to generate a peroxyacid, a stronger oxidant that allows the cleaning process to work effectively between 40 and 60 degrees Celsius.
Common Commercial Applications
Historically, sodium perborate was a widely used component in North American and European laundry detergents, functioning as a non-chlorine bleach. It was less aggressive than traditional sodium hypochlorite bleach, resulting in less damage to fabric dyes and fibers. This made it a fundamental ingredient in many powdered laundry and dishwashing detergents.
The oxidizing properties also made it an effective ingredient in personal care products, particularly oral hygiene items. It was commonly found in powdered denture cleaners and certain oral antiseptic rinses, where the release of active oxygen provided both bleaching and disinfectant effects. Dental professionals still use it for the internal bleaching of non-vital, root-treated teeth, placing the powder directly inside the tooth cavity.
The compound’s capacity to deliver a stable, solid source of peroxide has been applied to other areas, including use as a “disappearing” preservative in some ophthalmic solutions. In these eye drops, the perborate breaks down upon contact with the eye’s natural enzymes, leaving behind only water and oxygen. This ensures the solution remains sterile in the bottle without introducing persistent chemical preservatives to the eye.
Safety Considerations and Regulatory Status
While sodium perborate is an effective and stable cleaning agent, its safety profile has led to significant regulatory changes in many regions. The substance is classified as a reproductive toxicant, meaning it may damage fertility and the unborn child. This classification is primarily due to the borate component released upon hydrolysis in water.
In the European Union, sodium perborate is listed as a Substance of Very High Concern (SVHC) under the REACH regulation. This designation has led to its restriction and near-elimination from most consumer products, such as laundry detergents, throughout the EU. The restriction forces manufacturers to seek alternative ingredients.
The industry has largely transitioned to using sodium percarbonate in its place, particularly for cleaning applications. Sodium percarbonate also releases hydrogen peroxide when mixed with water, but it breaks down into sodium carbonate and hydrogen peroxide, avoiding the borate component. Although sodium percarbonate was historically less stable in detergent formulations than sodium perborate, advances in coating technology have made it a viable and safer substitute.