What is Sterile Alcohol (IPA)?

The World Health Organization defines sterility as the absence of living microorganisms. However, achieving complete sterility requires conditions that can often harm active ingredients. Therefore, sterility may be considered different based on the product’s functions. In the pharmaceutical industry, a container of alcohol is sterile if the chance of it being contaminated with replicating microorganisms is less than one in a million.

Sterility testing uses very sensitive methods. These methods typically involve incubating samples in growth media that allow various microorganisms to grow, making it easy to see any growth. Additionally, sterility involves operating procedures and environments that effectively prevent the contamination of alcohol or other products by biological materials. These procedures include using cleanroom spaces, air filtration, barrier-type equipment, and following Good Manufacturing Practices (GMP).

The probability of a product being nonsterile after sterilization is known as the sterility assurance level (SAL). The SAL is a statistical measurement of how likely a sterilized item is to contain a viable microorganism. For example, isopropyl alcohol is to be considered sterile if the SAL is 10−6, which means there is less than a one-in-a-million chance that the product is non-sterile. For manufacturers of sterile alcohol, the sterilization process must be validated to ensure it meets the standards of the American National Standards Institute (ANSI), the International Organization for Standardization (ISO), and the U.S. Food & Drug Administration (FDA).

Several methods are available for sterilizing products, with the two most popular combinations of techniques for producing sterilized isopropyl alcohol (IPA) being micron filtration and gamma irradiation. Isopropyl alcohol should not be sterilized by heating it under pressure in an autoclave. This method is not recommended for flammable liquids like alcohol. Most equipment manufacturers explicitly state that autoclaving flammable, reactive, corrosive, or toxic chemicals, such as alcohol, is unsafe. For example, autoclaving ethanol vapors can pose a significant fire risk.

The first method of sterilizing alcohol properly is sterile filtration. This highly precise process uses specialized filters to remove microorganisms like bacteria and microbial contamination from a liquid. The filters have pores small enough to trap these and other contaminants. Generally, the alcohol is filtered through a 0.2-micron sterile in-line filter, eliminating most bacteria. They are unable to pass through the pores on these filters.

Gamma irradiation is the subsequent method for sterilizing alcohol. This process utilizes high-energy electromagnetic radiation to eliminate microorganisms from products, making it commonly used to sterilize medical devices and pharmaceutical products.

Gamma irradiation damages microorganisms’ DNA, targeting their cell nuclei and causing defects. This method is carried out in approved sterilization facilities using a cobalt-60 radiation source. The amount of radiation applied to a product varies depending on its type and how it is packaged.

Gamma irradiation’s main advantages are that it is both safe and cost-effective, providing a secure and efficient method for sterilizing already-packaged items, such as bottles of alcohol or presaturated alcohol wipes. However, there are some drawbacks. There is a chance that the radiation can damage the materials being sterilized, resulting in unwanted changes to the product’s color, solubility, and texture. Additionally, there are safety concerns regarding the exposure of workers to radiation.

Sterile alcohols typically consist of a mixture of isopropyl alcohol (IPA) and either deionized (DI) water or water for injection (WFI). Sterile isopropyl alcohol is specifically formulated to effectively remove residues and clean and disinfect hard, non-porous surfaces in pharmaceutical manufacturing areas. Regardless of the sterilization method used, sterile alcohols should always be processed in a cleanroom, and all related packaging must undergo terminal sterilization using gamma irradiation. Sterile alcohol is available in various forms, including aerosols, spray bottles, capped containers, and presaturated wipes.

For more information on sterile and filtered alcohol wipes suitable for cleanrooms, we provide various ready-to-use options, including sterile isopropyl alcohol and sterile ethanol.