Quaternary ammonium compounds are a family of antimicrobial compounds that are strong cationic active agents in terms of their powerful disinfectant activity since they eliminate gram-positive and gram-negative bacteria (although the latter to a lesser degree.) They are bactericidal, fungicidal and virucidal. These compounds are active in both acidic and alkaline forms, although the alkaline is more effective. They are compatible with cationic surfactants, but not ionic and amphoteric ones.
Quaternaries are generally colorless or yellowish, and are not irritants or deodorants. Because of their chemical structure they tend to gel at low temperatures but become liquid again as they warm. They also have a detergent action and are soluble in water and alcohol. Quaternaries have the basic structure of the ammonium ion (NH4) which, when modified, give rise to different generations.
Benzalkonium chloride was the first compound of the derivatives of quaternary ammonium introduced in the market. Also known as N-Alkyl Dimethyl Benzyl Ammonium Chloride, this alkyl chain may have composition variations in the carbon number. The alkyl chains of twelve and fourteen carbons are the more powerfully antibacterial. This molecule is widely used as a hospital and veterinary disinfectant, as well as for bactericidal deodorant foot powder and topical disinfectants.
Quaternary ammonium compounds called second generation (ethylbenzyl chloride) and third generation (mixed first and second generation, i.e., benzalkonium chloride and alkyldimethylbenzylammonium chloride) are the compounds that remain most active in the presence of hard water. Their bactericidal action is attributed to the inactivation of enzymes, denaturation of essential proteins and cell membrane rupture. They are usually regarded as a disinfectant in concentrations of 0.25% to 1.6% for disinfecting surfaces such as floors and walls. The quaternary third generation have an increased biocidal activity detergency and increased bacterial resistance to constant use of a single molecule.
The fourth generation quaternaries are known as "Twin or Dual Chain Quats" or "twin chain" quaternaries, with chains that are dialkyl linear and without the benzene ring. These include Dimethyl Ammonium Chloride, Dioctyl Dimethly Ammonium Chloride, Didecyl Dimethyl Ammonium Chloride, each one isolated. These quaternaries have superior germicidal activity, are low foaming and have a high tolerance to protein loads and hard water. They are recommended for disinfection in the food and beverage industry, given their low toxicity.
Finally, the fifth generation quaternaries are mixtures of the fourth generation with the second generation, i.e., didecyldimethylammonium chloride, alkyldimethylbenzylammonium chloride, ammonium chloride, alkylbenzyldimethylammonium chloride, and other varieties according to the formulations. The fifth generation has a greater germicidal performance in unfavorable conditions and is safe to use.
Quaternaries have diverse uses, which include the following:
- General sanitation of utensils and equipment
- Disinfection in hospitals, and for toilets and medical instruments
- Disinfection in processing plants for meat and food, milk products and related industries
- Disinfection of clothing in laundries, hospitals, homes, etc.
- Control and prevention of mold in foot baths
- Control of algae in pools and in industrial water recirculation systems
- Antiseptics to disinfect skin and udders of cows and the hands of personnel involved in milking
- Control of slime caused by bacteria commonly found in industrial processes
- Textile and paper industries, in order to impart bacteriostatic properties by controlling and inhibiting microbial growth
- Control of microorganisms found in the injection water used in secondary oil recovery
Organo Sintesis, S. A. de C. V., (OSSA) is a company focused on research, development, distribution and sale of fine chemicals, meeting the demands of the pharmaceutical, cosmetics, soaps and detergents, and water treatment industries. Among its leading products are quaternaries of ammonium (first through fifth generation) and benzalkonium chloride.
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