出典(authority):フリー百科事典『ウィキペディア（Wikipedia）』「2013/07/07 00:07:50」(JST)
A detergent is a surfactant or a mixture of surfactants with "cleaning properties in dilute solutions."[1] These substances are usually alkylbenzenesulfonates, a family of compounds that are similar to soap but are more soluble in hard water, because the polar sulfonate (of detergents) is less likely than the polar carboxyl (of soap) to bind to calcium and other ions found in hard water. In most household contexts, the term detergent by itself refers specifically to laundry detergent or dish detergent, as opposed to hand soap or other types of cleaning agents. Detergents are commonly available as powders or concentrated solutions. Detergents, like soaps, work because they are amphiphilic: partly hydrophilic (polar) and partly hydrophobic (non-polar). Their dual nature facilitates the mixture of hydrophobic compounds (like oil and grease) with water. Because air is not hydrophilic, detergents are also foaming agents to varying degrees.
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Detergents are classified into three broad groupings, depending on the electrical charge of the surfactants.
Typical anionic detergents are alkylbenzenesulfonates. The alkylbenzene portion of these anions is lipophilic and the sulfonate is hydrophilic. Two different varieties have been popularized, those with branched alkyl groups and those with linear alkyl groups. The former were largely phased out in economically advanced societies because they are poorly biodegradable.[2] An estimated 6 billion kilograms of anionic detergents are produced annually for domestic markets.
Bile acids, such as deoxycholic acid (DOC), are anionic detergents produced by the liver to aid in digestion and absorption of fats and oils.
Cationic detergents are similar to the anionic ones, with a hydrophobic component, but, instead of the anionic sulfonate group, the cationic surfactants have quaternary ammonium as the polar end. The ammonium center is positively charged.[2]
Non-ionic detergents are characterized by their uncharged, hydrophilic headgroups. Typical non-ionic detergents are based on polyoxyethylene or a glycoside. Common examples of the former include Tween, Triton, and the Brij series. These materials are also known as ethoxylates or PEGylates. Glycosides have a sugar as their uncharged hydrophilic headgroup. Examples include octyl-thioglucoside and maltosides. HEGA and MEGA series detergents are similar, possessing a sugar alcohol as headgroup.
Zwitterionic detergents possess a net zero charge arising from the presence of equal numbers of +1 and −1 charged chemical groups. Examples include CHAPS.
See surfactants for more applications.
One of the largest applications of detergents is for cleaning clothing. The formulations are complex, reflecting the diverse demands of the application and the highly competitive consumer market. In general, laundry detergents contain water softeners, surfactants, bleach, enzymes, brighteners, fragrances, and many other agents. The formulation is strongly affected by the temperature of the cleaning water and varies from country to country.
Both carburetors and fuel injector components of Otto engines benefit from detergents in the fuels to prevent fouling. Concentrations are about 300 ppm. Typical detergents are long-chain amines and amides such as polyisobuteneamine and polyisobuteneamide/succinimide.[3]
Reagent grade detergents are employed for the isolation and purification of integral membrane proteins found in biological cells. Advancements in the purity and sophistication of detergents have facilitated structural and biophysical characterization of important membrane proteins such as ion channels,[4] transporters, signaling receptors, and photosystem II.[5]
Soapless soap refers to a soapfree liquid cleanser with a slightly acidic pH.[6] Soapless soaps are used in an array of products.
Phosphates and phosphorus compounds are one of the major chemical components in cleaning products, because these are known to minimize water hardness and to enhance cleaning efficiency. Phosphate-containing compounds are also one of the most commonly used complex agents to enhance the washing process.
Yet, detergents and old cleaning water are often poured out into aquatic bodies through water treatment plants, and phosphates are essential nutrients for aquatic organisms. But excess phosphates into aquatic bodies leads to an excessive amount of nutrients, and eutrophication, a sudden growth of algae leading to an unbalanced aquatic ecology and undesirable water quality. To avoid this problem, countries and economic zones such as the European Union or the United States have proposed or voted regulations to limit the use of phosphates and phosphorus compounds in household as well as industrial detergents.[7].
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