Why Is 70% IPA a Better Disinfectant than other concentrations?
What is Isopropyl Alcohol (IPA)?
Isopropyl alcohol or 2-propanol is an isomer of 1-propanol. It is a colorless, flammable, chemical compound with a strong odor having disinfectant properties. As an isopropyl group linked to a hydroxyl group, Isopropyl alcohol is the simplest example of a secondary alcohol, where the alcohol carbon atom is attached to two other carbon atoms. It is used in the manufacture of acetone and its derivatives and as a solvent. Tropically, it is used as an antiseptic. Small amounts of this alcohol are produced naturally by gut microbial flora. IPA widely used disinfectant within pharmaceutics, hospitals, clean rooms, and electronics or medical device manufacturing. Different solutions, purity grades, concentrations, and alcohol types yield beneficial cleaning and disinfection properties when applied correctly; or dangerous consequences when used improperly.
Properties of IPA:
Isopropyl alcohol, synonymous with 2-propanol, sec-propyl alcohol, IPA, isopropanol, or rubbing alcohol is miscible in water, ethanol, ether, and chloroform. It will dissolve ethyl cellulose, poluvin butyral, many oils, alkaloids, gums, and natural resins. Unlike ethanol or methanol, isopropyl alcohol is not miscible with salt solutions and can be separated from aqueous solutions by adding a salt such as sodium chloride. The process is colloquially called salting out and causes concentrated Isopropyl alcohol to separate into a distinct layer.
Isopropyl alcohol forms an azeotrope with water, which gives a boiling point of 80.37 °C (176.67 °F) and a composition of 87.7 wt% (91 vol%) isopropyl alcohol. Water-isopropyl alcohol mixtures have depressed melting points. It has a slightly bitter taste and is not safe to drink.
Isopropyl alcohol becomes increasingly viscous with decreasing temperature and will freeze at −89 °C (−128 °F).
Isopropyl alcohol has a maximum absorbance at 205 nm in an ultraviolet-visible spectrum.
Why Is 70% IPA a Better Disinfectant than other concentrations?
The optimum concentration for disinfection purposes is between 60%-90% solution in water v/v. typically 70% of solutions are used. Higher concentrations of alcohol are in fact less effective at killing bacteria. There is a number of reason for the use of 70% IPA.
1. Longer Evaporation Time:
100% IPA takes a longer time to evaporate from any surface hence get enough contact time and in this meantime, it shows its efficacy but in case of 100% IPA, evaporation will be very fast, the contact time will be less and it will not be so effective against microbes. Methyl alcohol has three times the vapor pressure than that of IPA. This means even at room temperature methyl alcohol will evaporate at a much more rapid pace, making it difficult to keep cleanroom damp enough to efficiently remove surface particles. A problem with methyl alcohol having a higher vapor pressure, more of the alcohol will be in the vapor state. This means the cleanroom operator would be exposed to stringent alcohol fumes.
2. Dissolve the plasma membrane of the cell wall:
The important thing is that only a 70% IPA solution of acts as a disinfectant killing all surface microorganisms. 70 % IPA solution kills microorganisms by dissolving the plasma membrane of the cell wall. The plasma membrane of gram-negative bacteria consists of a thin layer of peptidoglycan that easily destroyed by alcohol.
3. Denature the proteins:
100% IPA can’t denature the proteins Water plays a key important role which used to denature the proteins of the cell membrane and acts as a catalyst in the reaction. The contact time of the alcohol with the organism also plays an important role. A 70% solution of alcohol takes more time in evaporation from the surface, increasing the contact time. Therefore, “70% IPA” fulfills both requirements. The 100% isopropyl alcohol coagulates the proteins instantly by creating a protein layer that protects the other proteins from further coagulation. Due to this microbes are not killed but remain in the dormant stage.
4. Penetration Power:
Other concentration IPA cannot be entered into the cell completely. 70% IPA solutions penetrate the cell wall more completely which permeates the entire cell, coagulates all proteins, and therefore the microorganism dies.
These are the main causes of “Why Is 70% IPA a Better Disinfectant than other concentration?”
References:
1. “Disinfection & Sterilization Guidelines”. Guidelines Library: Infection Control. CDC. 28 December 2016. Archived from the original on 12 January 2018. Retrieved 12 January 2018.
2. Tortora, G.J., Funke, B.R., Case, C.L. and Johnson, T.R., 2004. Microbiology: an introduction (Vol. 9). San Francisco.
3. Soaking in 70% solution 15 minutes destroyed vegetative bacteria on endotracheal tube cuffs (Zieglar & Jacoby, 1956)
3. “Spaulding who demonstrated using the mucin-loop test that 70% isopropyl alcohol destroyed 104 M. tuberculosis in 5 minutes” (Rutala et al., 2008)
These are the main causes of “Why Is 70% IPA a Better Disinfectant than other concentration?”
References:
1. “Disinfection & Sterilization Guidelines”. Guidelines Library: Infection Control. CDC. 28 December 2016. Archived from the original on 12 January 2018. Retrieved 12 January 2018.
2. Tortora, G.J., Funke, B.R., Case, C.L. and Johnson, T.R., 2004. Microbiology: an introduction (Vol. 9). San Francisco.
3. Soaking in 70% solution 15 minutes destroyed vegetative bacteria on endotracheal tube cuffs (Zieglar & Jacoby, 1956)
3. “Spaulding who demonstrated using the mucin-loop test that 70% isopropyl alcohol destroyed 104 M. tuberculosis in 5 minutes” (Rutala et al., 2008)
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Is 70 percent isopropyl alcohol still effective after expiration date
Great discussion…