Quaternary ammonium compounds

Chemical structure
By reason of their chemical structure, QAC’s belong to the surfactants. They are characterized by a (polar) ammonium group, whose four hydrogen atoms are replaced by organic moieties like more or less long alkyl moieties (apolar groups).

Benzalkonium chloride (BAC) belongs to the quaternary ammonium compounds (QAC) and is characterized by following chemical structure:

Characteristics
Surface active substances are tensides (detergents), which have a deterging molecule structure. They possess both lipophilic and hydrophilic parts. By concentrating on surfaces and edge surfaces between aqueous and non-aqueous media, quaternary ammonium compounds decrease the surface energy.

Amines and quaternary ammonium compounds (QAC), which belong to the cationic tensides, rank among the surface active substances, which play a role in disinfection.

QAV
The best known quaternary ammonium compound used for disinfection is alkyl dimethyl benzyl ammonium chloride (benzalkonium chloride). An antimicrobial effect is only given, when at least one of the four moieties possesses a chain length of 8-18 atoms.

Effect mechanisms
The QAC’s antimicrobial characteristics are a consequence of the cationic charge, which electrostatically bonds to the negatively charged parts of the cell wall. Firstly, QACs attach to the cell surface, then they penetrate the cell wall, bond to the cytoplasm membrane and destroy it. The cytoplasm’s parts are resolved and flushed out. In addition the semi-permeability of the cell membrane is disturbed and the cell membrane is dissolved respectively. The destruction of the intact cell structure finally results in the cell’s death.

Fields of application
As tensides QACs have both a detergent and disinfecting effect. The QACs’ limited spectrum of effect is restricted to vegetative bacteria and enveloped, lipophilic viruses (incl. HIV). QACs feature many advantages, e.g. minor human toxicity, skin and material compatibility as well as odorlessness. In combination with other disinfecting agents the QACs’ positive application characteristics synergetically unite with the superior spectrum of effect of other substances. Together with alcohols and aldehydes, QACs can for example achieve an increase and prolongation of activity. Formulations in combination with QACs are used for hand disinfection, preliminary instrument cleaning, surface disinfection and skin disinfection.

Amines
Amines are the organic derivates of ammonia. Alkyl amines (also referred to as fatty amines) are generally made of fatty acid. If the hydrogen atoms are replaced by further alkyl moieties in the alkyl amine, one gets a secondary or tertiary alkyl amine. Substances, which contain two or three amine groups, are referred to as diamine or triamine, whereas the chemical moieties at the nitrogen atom can be of aliphatic or aromatic nature.

Effect mechanisms
As surface active substances, amines concentrate on the surfaces of two media and decrease their surface energy. Thus the media can better interlink. The effect mechanism corresponds with the one of QACs (see above). Among the different amines, alkyl amines possess a broad antimicrobial spectrum of activity and a rapid effect.

Fields of application
Due to their characteristics such as microbiological efficacy, material compatibility, cleaning performance and foaming characteristics, amines are used for surface and instrument disinfection, in pharmaceuticals and colorings, as wetting and emulsifying agent or detergent. By combining almines among themselves or with other disinfecting agents, synergetic effects are achieved with regard to the optimization of application characteristics.