The Difference Between Isopropyl Alcohol (IPA) 99% and 70%

Isopropyl Alcohol or 2-Propanol is a very commonly used disinfectant within pharmaceutical companies, hospitals and cleanrooms. It is even used in the purification of electronics and medical device manufacture. It has a number of different purity grades and they are designed for different use. They are beneficial cleaning chemicals and disinfectants, and depending on how concentrated they are, they can get rid of all sorts of bacteria and impurities. 

The two that this article will focus on are the concentrations of 70% and 99% Isopropyl alcohol. 

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70% Isopropyl Alcohol


Between the concentrations of 60% and 90%, Isopropyl alcohol is a very effective agent against microbial bacteria, fungi, and viruses. Higher concentrations don’t generate a much more desirable effectiveness against bacteria, fungi and viruses. This is because, there has to be a significant enough presence of water with the Isopropyl alcohol in order to be effective. And this percentage of water needs to be at least more than 10% within the solution. And the mixture of 30% water with 70% Isopropyl alcohol works best

The reason water is so important is because it acts as a catalyst and has a major role in denaturing the proteins of cell membranes of vegetative cells. 70% IPA solutions are very effective in breaching the cell wall fully. Also, the presence of water slows down evaporation and increases the surface contact time with the membrane. With 91% IPA, the evaporation is instant and protein coagulates, rendering the effect of the IPA greatly reduced.

This means that 91% IPA takes a greater time to act and doesn’t kill as much bacteria as 70% IPA. The latter is also cheaper.

99% Isopropyl Alcohol


This concentration of IPA is not as commonly used as a disinfectant, but as a solvent or cleaning agent for industries that produce products that are sensitive to water. Hence, it makes sense to use a hydrophobic solvent. It also has a very low flash point and hence, evaporates rapidly. 

This is useful in computer and electronics manufacturing industries that prefer immediate evaporation of cleaning agents for their work. During the design work for chips and circuit boards and integrated circuits, there needs to be a quick clean up if something is spilled and the work area needs to be devoid of any contaminants or obstructions as soon as possible; 99% IPA ensures that happens.

Rapid evaporation has a downside to it since it reduces shelf life, but on the other hand, it ensures little to no dilution in alcohol content, and hence it is preferred for great consistency. 

Both these materials are non corrosive to metals and are plastic safe as well. They are ozone safe and have a low impact on the climate. They are both flammable, the 99% variant much more so because of its high flash point so they need to be stored in places without any danger of fire. 

Note: These chemicals are meant to be used for research, industrial work, cleaning or disinfecting, hence they shouldn’t be toyed with or kept near young children or infants. 

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