Why not we are using 60%,80% or other concentrations of IPA?
Due to the concentration difference of water and alcohol on either side of the cell wall, 70% alcohol enters the cell to denature both enzymatic and structural proteins.
Isopropyl alcohol (IPA) is widely used as a disinfectant in pharmaceutical companies. IPA is very effective on gram-positive as well as gram-negative bacteria. Most of the hand disinfectants available in the market contain IPA as an active component just because of its effectiveness. IPA is very effective and kill the microbial cell within a few seconds. But one limitation of IPA is that it is not effective against bacterial and fungal spores. Disinfectant efficacy depends upon two factors. First is concentration of disinfectant solution and second is contact time. Disinfectant validation activity also depends upon these two factors. In pharmaceuticals, that’s why validation activity must be performed to validate its effective concentration and contact time. Different guidelines and pharmacopeias recommend 70% IPA solution because at this particular concentration, IPA is very effective. But why 70% IPA is effective and recommended by pharmacopeias and guidelines why not 100 %? The reason is behind the mode of action of 70% IPA. Bacterial cells have proteins in their cell wall and when this protein comes in contact with the 70% IPA during disinfectant application, coagulation of proteins takes place in which denaturation of proteins occurred, and after that IPA penetrates the interior of the cell which causes lysis or death of the cell. Protein coagulation also happens in the case of 100% IPA but at a very fast rate and because of this very fast protein coagulation process denatured protein forms a protective layer outside of the cell. When this happens, 100% can not penetrate inside the cell and is not able to kill the microbe. Microorganisms become dormant in that conditions. In the case of 70% IPA protein coagulation takes place at a slow rate and due to this 70% IPA gets enough time to penetrate the cell and kill the microorganism. Another factor is contact time, 70% IPA takes a longer time to evaporate from any surface and hence gets enough contact time and in this meantime it shows its efficacy but in the case of 100% IPA, evaporation will be very fast, and contact time will be less and it will not be so effective against microbes. That’s why 70% IPA solution is used as a disinfectant in pharmaceutical industries.
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