Amphoteric surfactants are most commonly found inshampoos and bodywashes. These are the least potent surfactants, and are found in personal care products designed for sensitive skin. Nonoinic surfactants contain no charge. They are commonly found in laundry and dishwasher detergents. They are the second most widely used surfactants after anionic. They are generally less effective than anionic, but for some people cause less skin irritation. If anionic are the most popular surfactants, nonionic are a close second, widely used in a range of cleaning, personal care, and disinfectant products as well as industrial processes.
The most common anionic surfactants are:. In areas with hard water high mineral content , nonionic surfactants are more heavily marketed, as they are less likely to form a soap scum . The nonionic surfactants are less likely to cause skin irritation, but this is associated with a less potent cleaning ability.
Most cleaning products blend anionic and nonionic surfactants to balance cleaning potential with the risk of skin irritation. In most countries, there is no legal requirement for cleaning products to specify which surfactants they use including the US and EU. We will only review products that have full ingredient disclosure. The following are examples of common cleaning product labels — showing the extent of available information in mainstream laundry detergents.
Surfactants are used in cleaning products to reduce surface tension, helping to wash away oil and grease. There are four main categories of surfactant, ionic anionic, cationic, and amphoteric and nonionic. Anionic are the most widely used and potent, but they are associated with skin irritation. Very few cleaning products list their surfactants and are not currently compelled to do so by law in either the US or EU. Instead, ingredient label list the overall blend of surfactants, making it impossible to avoid particularly harsh or allergenic ingredients.
So stick with us for now. There is change afoot with legistlaion, but in the meantime, we will only review products that have full ingredient disclosure. We will give our opinion on these ingredients, and we will tell you how well they clean.
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Surfactants in consumer products: Theory, Technology and Application. Biodegradability, toxicity and mutagenicity of detergents: integrated experimental evaluations. Ecotoxicology and Environmental Safety, 84, Cleansers and their role in various dermatological disorders. Indian Journal of Dermatology, 56 1 , 2. Our resident pharmacist.
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This site uses Akismet to reduce spam. Historically these included branches in the side chains with the result that they biodegrade very slowly and lead to foaming in rivers and sewage plants. By law, in most countries today, the surfactant must have side chains which are not branched so they degrade more rapidly. Straight chain alkenes for the above process can be produced from ethene using a Ziegler catalyst triethyl aluminium. Triethyl aluminium reacts with ethene at ca K and atm to form aluminium alkyls, for example:. When heated in excess ethene, straight chain alkenes, with the double bond at the end of the chain an a-alkene , are produced:.
The mixture is then separated into fractions by distillation, the fraction of alkenes containing 10 to 14 carbon atoms being used to make the surfactants. These are used together with other surfactants in powder and liquid laundry detergents such as Ariel, Daz, Persil and Surf. Many detergent products, particularly liquids, contain other synthetic anionic surfactants such as alkyl sulfates, esters of linear alcohols C 10 -C 18 and sulfuric acid.
The alkyl sulfates are also used in personal care products such as toothpaste and are manufactured by treating the alcohol with sulfur trioxide. The product is then neutralised with aqueous sodium hydroxide solution to form a sodium alkyl sulfate:. The alcohols are either produced from carboxylic acids obtained from oils, obtained naturally, for example from palm kernel oil or coconut oil, or alternatively from long-chain alkenes, manufactured from ethene.
There are two processes for making the alcohols from ethene. As described above, aluminium triethyl reacts with ethene to produce compounds such as:. Instead of heating with excess ethene to produce a-alkenes, the aluminium alkyl is treated with oxygen and then water to produce long chain alcohols:.
In the first stage, ethene is passed, under pressure of ca atm, into a solvent usually a diol, such as butane-1,4-diol containing a nickel salt at K. It yields a mixture of a-alkenes which are separated by fractional distillation. These are reacted with carbon monoxide and hydrogen hydroformylation to yield straight-chain aldehydes, which on reduction form alcohols. For example:. It is possible to convert the other a-alkene fractions C 4 -C 10 and C 14 -C 40 into the more desirable C 10 -C 14 fraction.
More widely used than simple alkyl sulfates are various types of sodium alkyl ether sulfates SLES. In the manfacture of SLES the primary alkyl alcohol from a synthetic or natural source and typically a blend based around dodecanol is first ethoxylated with 1 to 3 molar equivalents of epoxyethane as described below for the manufacture of nonionic surfactants. The product is then sulfated using sulfur trioxide and neutralized with alkali to form the alkyl ether sulfate:. These materials are preferred by product formulators for many applications dishwashing liquids, shower gels, shampoo, etc because they are milder to the skin than alkyl sulfates.
They also generate less foam which is an advantage in the formulation of laundry machine products. Although they are produced in much smaller quantities than the anionics, there are several types, each used for a specific purpose. An alkyl quaternary nitrogen system has alkyl groups attached to the nitrogen atom.
An example is:. The directly quaternised fatty acid surfactants described above have been replaced for laundry applications by more complicated structures in which there is an ester linkage between the alkyl chains and the quaternary head-group as these are more biodegradable and less toxic. They are known as esterquats. These surfactants do not bear an electrical charge and are often used together with anionic surfactants. An advantage is that they do not interact with calcium and magnesium ions in hard water. The major group of nonionics are the ethoxylates made by condensing long chain alcohols with epoxyethane ethylene oxide to form ethers, for example:.
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Although they do not contain an ionic group as their hydrophilic component, hydrophilic properties are conferred on them by the presence of a number of oxygen atoms in one part of the molecule which are capable of forming hydrogen bonds with molecules of water. As the temperature of the surfactant solution is increased the hydrogen bonds gradually break causing the surfactant to come out of solution. This is commonly referred to as the cloud point and is characteristic for each nonionic surfactant.
Nonionics are more surface active and better emulsifiers than anionics at similar concentrations. They are less soluble than anionics in hot water and produce less foam. They are also more efficient in removing oily and organic dirt than anionics. Depending on the type of fibre, they can be active in cold solution and so are useful in countries which lack hot water supplies and in developed countries where there is a desire to lower the wash temperatures either to save energy or because of the type of fabric being washed.
Nonionics are used in fabric washing detergents both powders and liquids , in hard surface cleaners and in many industrial processes such as emulsion polymerization and agrochemical formulations. Amphoteric or zwitterionic surfactants are so called because the head-group carries both a negative and positive charge.
A range of methods is used to produce such materials, almost all of which contain a quaternary ammonium ion a cation. One such well-used class is the alkyl betaines which have a carboxyl group. A long-chain carboxylic acid reacts with a diamine to form a tertiary amine. On further reaction with sodium chloroethanoate, a quaternary salt is formed:.
Measuring Anionic Surfactants
Betaines are neutral compounds with a cationic and an anionic group which are not adjacent to one another. Amphoteric surfactants are very mild and are used in shampoos and other cosmetics. They are said to be pH balanced. A detergent is made up of many ingredients, some of which are surfactants.
What are surfactants and how do they work?
An example of the mixture of compounds in a detergent is shown in Table 1. In this formulation there are seven surfactants, two anionic, three non-ionic and two soaps. However, there are other ingredients, each with specific functions:. Some detergents need anti-caking agents, for example aluminium silicate, which keep the powder dry and free-flowing.
Builders , usually sodium aluminosilicates, a type of zeolite , remove calcium and magnesium ions and prevent the loss of surfactant through scum formation. Stains can be bleached with oxidizing agents such as sodium perborate NaBO 3. However bleach activators are needed for low temperature washes. Sodium perborate and sodium percarbonate do not liberate hydrogen peroxide in cool water. A compound is added to react with them to liberate a peroxycarboxylic acid, RCO 3 H, which oxidizes stains readily.
The most commonly used activator is:. It is known by its trivial name, TAED, and reacts with the oxidizing agent to form peroxyethanoic acid:. Sequestrants - to react with free metal ions which might otherwise cause problems with appearance or scum formation. Enzymes - to remove specific stains: proteases to remove proteins , amylases to remove starches , lipases to remove fats.
Domestic automatic machine laundry liquids are formulated using blends of anionic, nonionic and soap surfactants and various other functional substances. Bleach systems are not compatible with the higher water temperature and cannot be used above ca K. For hand washing used for delicate fabrics such as wool or silk , foam-stabilisers are included, to maintain foam.
Related Anionic surfactants
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