Why 70% IPA is widely used as a disinfectant?

Why 70% IPA is widely used as a disinfectant rather than 100% pure IPA in the pharmaceutical, healthcare industries. 70% IPA (Isopropyl Alcohol) is commonly used for disinfection purposes. The range of 50% to 91% IPA is more effective than 100% IPA. 70% IPA is universally accepted as a disinfectant. To disinfect equipment surface, hand, area, etc. 70% IPA is used.

1.0 What is Isopropyl Alcohol (IPA)?

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

  • Synonym – 2-propanol, Isopropanol
  • Chemical formula- CH3CHOHCH3
  • Miscibility – Isopropyl Alcohol is Miscible with water, alcohol, ether and chloroform.
  • Taste – Slightly bitter
2.0 How to prepare 70% IPA?

Take 100 ml of measuring cylinder put 70 ml of IPA (100% pure) into the cylinder and make up the volume with purified or distilled water. It means 70 ml IPA and 30 ml water.

3.0 Use of Isopropyl Alcohol (IPA)

3.1 IPA is used as disinfectant. In most industries like pharmaceutical, healthcare, medical devices, etc. 70% IPA is used for sanitization purposes.

3.2 IPA is used as a solvent for many products, materials.

3.3 IPA acts as local anesthetics (not widely used)

3.4 IPA is used as antiseptic to prevent infection occur due to cuts, burn, scrapes.

4.0 How 70% IPA work as a disinfectant

4.1 Bacteria contain a plasma membrane and this plasma membrane is protecting the cell from the outer environment.

4.2 Cell plasma membrane is soluble in the 70% IPA.70% isopropyl alcohol, 70% IPA, Why 70% IPA is widely used as a disinfectant?

4.3 After the dissolution of the cell membrane 70% IPA enters into the cell and kills the bacteria. Hence, 70% IPA acts as a bactericidal agent.

5.0 Why 70% IPA is widely used as a disinfectant
5.1 Increases evaporation time

100% pure Isopropyl Alcohol evaporates faster than 70% Isopropyl Alcohol because of water is delaying the evaporation rate of Isopropyl Alcohol. Ultimately, increases the evaporation time. Also, increase contact time of 70% IPA with the bacteria. Which shows better results as a disinfectant.

5.2 Coagulation of protein:

100% IPA is instantly coagulating the protein due to this protein produce protecting layer which protects the remaining amount of the protein from coagulation. Bacteria adapt to the dormant stage (temporarily stop the growth and physical activity of bacteria) in which bacteria are not killed. In case of 70% IPA the rate of coagulation of protein is slowed down.

5.3 Water acts as a catalyst:

Water acts as a catalyst in 70% IPA which increases the penetration rate of the cell membrane. Hence, increases the killing rate of bacteria.

5.4 Cost-effective

30% water is used for the preparation of 70% IPA which is more cost-effective than 100% IPA.

6.0 Most effective range of Isopropyl Alcohol (IPA)

6.1 Most effective range of Isopropyl Alcohol is 50% to 91%.

6.2 It is experimentally proved that the Staphylococcus aureus is killed in case of below concentration range:

  • 50% Isopropyl Alcohol – less than 10 seconds
  • 90% solution – not killed in 2 hours

6.3 50% IPA is more effective than 90% IPA. It proves the importance of water in killing microorganisms.

6.4 Another range of IPA 10%, 20%, 30%, 100% fails to kill the microbes.

6.5 While 70% IPA is effective on broad spectrum of microbes.

6.6 The killing time of microbes is vary based on type of microbes. Refer page no. 238 for more details about the killing time of microbes.

7.0 Evaluation method for Validity of 70% Isopropyl Alcohol Solution:

7.1 Validity of 70% IPA is decided based on the hold time study conducted by the manufacturing site. A study should be conducted for 0 hr, 24 hrs, 48 hrs, 72 hrs, 96 hrs likewise. Based on the study manufacturing site decide the validity for 70% IPA.

7.2 Generally, for nonsterile area 70% IPA is used within 7 days and for sterile area 70 % IPA is used within 24 hrs (prepare on daily basis) and discard remaining 70% IPA at the end of the day.

8.0 Permissible limit of 100% Isopropyl Alcohol:

Average daily permissible limit for pure Isopropyl alcohol is 0.6 mg/m3 .


Disinfection, Sterilization, and Preservation – Google Books, Page no. 238

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