Why 70 Percent Isopropyl Alcohol is used as disinfectant
Why 70 Percent Isopropyl Alcohol is used as disinfectant

Why is 70% IPA such a popular disinfectant?

General information about Isopropyl Alcohol (IPA)

IPA is a type of alcohol that is a transparent, colorless, mobile, volatile, flammable liquid having a strong odor.


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Synonyms: IPA are 2-propanol, and Isopropanol, isopropanol, sec-Propyl alcohol, IPA, Isopropanol, Isopropyl alcohol

Linear Formula: (CH3)2CHOH

CAS Number: 67-63-0

Molecular Weight: 60.10

Beilstein: 635639

EC Number: 200-661-7

MDL Number: MFCD00011674

PubChem Substance ID: 329760020


Miscibility: Isopropyl Alcohol is miscible with water, alcohol, ether, and chloroform.

Taste: Slightly bitter

Safety information – Pictograms

GHS02:  The GHS hazard pictograms for free download

GHS07:  Wax Melts Manchester - Product Safety - BlueBird Candles

Signal Word: Danger

Hazard Classifications:

Eye Irrit. 2 – Flam. Liq. 2 – STOT SE 3

Target Organs: Central nervous system

Storage Class Code: 3 – Flammable liquids


Flash Point(F): 53.6 °F – closed cup

Flash Point(C): 12.0 °C – closed cup

How is 70% isopropyl alcohol (IPA) prepared?

Take 100 ml of the measuring cylinder, fill it with 70 ml of 100% pure IPA, and then fill the remaining space with filtered or distilled water. It states that there are 70 ml of IPA and 30 ml of water in the 100 ml solution.

Isopropyl alcohol (IPA) is used for a variety of purposes.

As a disinfectant, IPA is utilized. 70% IPA is typically used for sanitization in sectors like pharmaceutical, healthcare, medical devices, etc.

IPA is employed as a solvent for the granulation, coating, or purification of active pharmaceutical ingredients (APIs) in the production of pharmaceutical formulations. It is also utilized as a washing agent during raw material manufacturing.

IPA is also employed as an antiseptic to stop the spread of infection from burns, scrapes, and other wounds. IPA is effective against many viruses, fungi, and most bacteria, but not bacterial spores.

The CDC recommends 70% for disinfecting one’s household and routine cleaning (CDC, 2020)

Why 70% IPA is effective as a disinfectant?

A plasma membrane is present in bacteria, and it shields the cell from its surroundings. In 70% IPA, the cell plasma membrane is soluble. 70% IPA penetrates the cell once the cell membrane dissolves and destroys the germs there. Thus, 70% IPA functions as a bactericidal substance. In other words, 70% IPA kills organisms by causing their lipids and proteins to denature.

The ideal bactericidal concentration is 60%-90% solutions in water (volume/volume), and their cidal action declines significantly below 50% concentration.

Source: https://www.cdc.gov/infectioncontrol/guidelines/disinfection/disinfection-methods/chemical.html

The mode of action

The most reasonable explanation for alcohol’s antibacterial activity is protein denaturation. This process is confirmed by the fact that pure IPA, a dehydrating agent, is less bactericidal than alcohol-water combinations because proteins denature faster in the presence of water. Protein denaturation is also compatible with data that alcohol kills Escherichia coli dehydrogenases, enhancing the lag phase of Enterobacter aerogenes. This may be reversed by adding specific amino acids. The bacteriostatic activity was thought to be produced by suppressing the generation of metabolites required for fast cell division.

Why is 70% IPA used so frequently as a disinfectant rather than 90% or 100%?

Increases evaporation time:

Since 100% isopropanol (IPA) evaporates quickly, it is less effective in penetrating bacterial cell walls to destroy them and disinfect surfaces.

In other words, it degrades before entering the cell and attacking the infection.

In contrast to 70% IPA, it prolongs the evaporation process. Increase the amount of time that 70% IPA is in touch with the germs; this will improve the disinfectant’s effectiveness.

Coagulation of protein:

Utilizing the 100% concentrated solutions will almost immediately cause the proteins on the cell wall or surface to coagulate, blocking the entry of alcohol into the cell. Coagulation of the outer membrane prevents the virus or bacterium from allowing the isopropyl alcohol to pass through (Widmer and Frei, 2011). 

As a result, the virus or bacteria become more resistant to isopropyl alcohol due to the stronger isopropyl solution protecting them from its antiseptic qualities. In other words, at larger concentrations, external harm results in forming a shielding wall around the organism. The less efficient alcohol is as a disinfectant, the greater the concentration, the more diseases it can destroy.

Water acts as a catalyst:

In 70% IPA, water functions as a catalyst to speed up cell membrane penetration. They are increasing the rate at which germs are killed.


30% water is used to prepare 70% IPA, which is more cost-effective than 100% IPA.

In summary, 70% isopropyl alcohol is effective because it crosses the cell membrane, attacking the entire cell and killing the bacteria.

Reference: The Centers for Disease Control and Prevention (CDC) researched disinfecting and sanitizing methods and published the Guideline for Disinfection and Sterilization in Healthcare Facilities.

The following are the advantages of using 70% alcohol.

  • The alcohol is able to enter the cell because surface proteins coagulate more slowly.
  • Being a dilution of pure alcohol, 70% alcohol contains water, which is necessary for denaturing proteins.
  • 70% of the alcohol enters the cell to denature both enzymatic and structural proteins because of the differential in water and alcohol content on each side of the cell wall. This strengthens its antibacterial effects of it.

What are the Types of Isopropyl Alcohol?

Isopropyl alcohol (IPA) is available in various grades on the market. This comprises pharmaceutical (Pharmacopeial), ACS (Spectrophotometric grade), and industrial/ technical grade.

Pharmacopeial / Medical / Pharmaceutical Grade IPA

This IPA covers a wide range of uses, such as the manufacture of drugs, the production of medical wipes, cosmetics, and personal care items (toiletries). It is anticipated that its purity would be slightly greater than that of industrial grade.

All production facilities must maintain health authority registration and inspection, and rigorous regulations must be followed while manufacturing, packing, and storing products. These requirements increase reliability and security for usage in industrial, pharmaceutical, flavour and fragrance, or lab settings.

Industrial/ Tech Grade IPA

This kind of IPA is frequently used as a cleaning, industrial/technical solvent, and a starting point for derivatives. It has several non-medical uses, including general wiping and cleaning, printed circuit boards (PCBs), surface coatings, cleaning inks, and numerous household/commercial cleansers.

Industrial or Tech-Grade IPA is not permitted for use in food, medicine, or other products since it is subject to lesser purity regulations.

It’s a cost-effective solution for cleaning large surfaces and removing general pollutants like dust, dirt, oil, and adhesives from other production operations.

ACS (Spectrophotometric grade)

Compared to USP grade, ACS IPA adhered to a higher purity level. It is frequently used in products like rubbing alcohol, cosmetics, and personal care items (toiletries).

Disinfectant efficacy studies, also known as disinfectant validation studies

Disinfectant efficacy studies, also known as disinfectant validation studies, are carried out to show that the disinfectants used on surfaces in manufacturing areas, laboratories, and other facility areas effectively inactivate or remove microorganisms. 

The microorganisms include bacteria, fungi (Yeast and molds), bacterial spores, viruses, and mycoplasma.

What should be covered to perform Disinfectant Studies

i. Study Planning and Protocol Development: Identify the surfaces, pathogens, disinfectants, and testing conditions.

ii. Studies on surface efficacy: Analyze the efficacy of disinfectants on the relevant surfaces in inactivating the dehydrated microorganism.

iii. Studies on suspension-Efficacy: Analyze the disinfectant’s efficacy while it is in suspension (this is an optional test). This test gives pertinent information on the product’s effectiveness against non-dried microorganisms. Desiccated microorganisms could be under stress and present distinct difficulties.

iv. Use-Dilution Expiration Studies: Check the disinfectant’s efficacy before and after the specified expiration date.

The following controls are part of these studies

Controls for recovery: Determine how well the organisms applied to the surfaces can be recovered (conducted prior to or simultaneously with efficacy studies).

The controls for disinfectant neutralization, toxicity, and interference ensure that the sample matrix and disinfectants do not affect the assay’s performance for the organisms under investigation.


Simply explained, larger doses result in an exterior harm that creates a shielding wall around the organism. For this reason 70% IPA is most popular as it is effective at optimum concentration as well as cost effective.

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