Why 70% IPA is widely used as disinfectant? Why not 100% IPA not used ?
The most common using disinfectant in the pharmaceutical industries, hospitals and other health care facilities is 70% isopropyl alcohol. It is is used for disinfection of hands and equipment surface and surgical devices.
The important thing is that only 70% solution of IPA acts as a disinfectant killing all surface microorganisms and bacteria. 70% IPA solution kills microorganisms by dissolving the plasma membrane of the cell wall. Plasma membrane of gram negative bacteria consist of a thin layer of peptidoglycon that easily destroyed by the alcohol.
Water is plays key important role which used to denature the proteins of cell membrane and acts as a catalyst in the reaction. Contact time of the alcohol with the organism also play an important role. IPA are volatile in nature they are easily exposed or evaporate in envoirment when it open conditions. A 70% IPA takes more time in evaporation from the surface and increasing the contact time. Therefore, 70% IPA fulfills the both requirements.
The 100% isopropyl alcohol denature the cell wall of bacteria and coagulates the proteins instantly by creating a protein layer that protects the other proteins from further coagulation. Due to this microbes are not killed completely but it remains in dormant stage.
While 70% IPA solution penetrates in the cell wall at slower rate and coagulates the all protein of the cell wall and microorganism are completely dies.