Why Is 70% Isopropyl Alcohol (IPA) a Better Disinfectant than 99% Isopropanol, and What Is IPA Used For?


What Is Isopropyl Alcohol and How Is It Used?

Isopropyl alcohol (2-propanol), also known as isopropanol or IPA, is the most common and widely used disinfectant within pharmaceutics, hospitals, cleanrooms, 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. This post will help you identify key uses, best practices, and proper disinfection with isopropyl alcohol.

Why Is 70% the Most Effective Concentration of Isopropyl Alcohol for Disinfection?

Isopropyl alcohol, particularly in solutions between 60% and 90% alcohol and 10 – 40% purified water, is rapidly antimicrobial against bacteria, fungi and viruses. Once alcohol concentrations drop below 50%, usefulness for disinfection drops sharply. Notably, higher concentrations of alcohol don’t generate more desirable bactericidal, virucidal, or fungicidal properties.

The presence of water is a crucial factor in destroying or inhibiting the growth of pathogenic microorganisms with isopropyl alcohol. Water acts as a catalyst and plays a key role in denaturing the proteins of vegetative cell membranes. 70% IPA solutions penetrate the cell wall more completely which permeates the entire cell, coagulates all proteins, and therefore the microorganism dies. Extra water content slows evaporation, therefore increasing surface contact time and enhancing effectiveness. Isopropyl alcohol concentrations over 91% coagulate proteins instantly. Consequently, a protective layer is created which protects other proteins from further coagulation. Solutions > 91% IPA may kill some bacteria, but require longer contact times for disinfection, and enable spores to lie in a dormant state without being killed. A 50% isopropyl alcohol solution kills Staphylococcus Aureus in less than 10 seconds, yet a 90% solution with contact time of over two hours is ineffective. Some disinfectants will kill spores with exposures times that exceed 3-12 hours, which are classified as chemical sterilants. So why do higher alcohol solutions yield less results for bactericidal and antimicrobial outcomes?

Why Doesn’t Isopropyl Alcohol Kill Bacteria and Fungal Spores?


Some bacteria transform into spore cells when external conditions are unfavorable; the result is reduced metabolic activity, higher cidal resistance, and immunity from alcohol-based disinfectants. Spores lie dormant, and once conditions become favorable again, the microbe converts back to a vegetative state and grows actively. When examining the effectiveness of IPA, accurately translating its benefits and shortcomings require distinctions of identify, purity, sterility, and intended use. Disinfection, unlike sterilization, does not provide sporicidal attributes.

Is Sterilization with Isopropanol (AKA Isopropyl Alcohol or IPA) Possible?

Proper Uses of Isopropyl Alcohol Require Distinction Between Sterilization and Disinfection

Terms like disinfection and sterilization are often misunderstood and used interchangeably. The Center for Disease Control (CDC) defines terminology clearly:

Unlike sterilization, disinfection is not sporicidal. A few disinfectants will kill spores with prolonged exposure times (3–12 hours); these are called chemical sterilants. At similar concentrations but with shorter exposure periods (e.g., 20 minutes for 2% glutaraldehyde), these same disinfectants will kill all microorganisms except large numbers of bacterial spores; they are called high-level disinfectants. Antiseptics are germicides applied to living tissue and skin; disinfectants are antimicrobials applied only to inanimate objects. In general, antiseptics are used only on the skin and not for surface disinfection, and disinfectants are not used for skin antisepsis because they can injure skin and other tissues. Virucide, fungicide, bactericide, sporicide, and tuberculocide can kill the type of microorganism identified by the prefix. For example, a bactericide is an agent that kills bacteria. — CDC

Isopropyl alcohol is excluded from classification as a high-level disinfectant because of its inability to eradicate bacterial spores and hydrophilic viruses such as polio. It’s low-level categorization outlines effectiveness for non-critical patient care devices such as blood pressure cuffs.

Why Not Use Higher Isopropyl Alcohol (91%+) Concentrations?

Isopropyl Alcohol

70% isopropyl alcohol upholds key requirements for use as a bactericidal in cleanrooms or medical facilities, but also for general purposes. 70% IPA/30% water solutions produce less vapor and odor, therefore reducing risks of toxic fumes or combustion. When isopropyl alcohol reacts with air, light, and oxygen, it forms unstable peroxides which increases the likeliness of explosion, especially when heated with aluminum. IPA volatility increases with storage time and alcohol concentration, especially when exposed to light over multiple years after opening. 70% IPA is not only less flammable, but also offers a more economical price point for general wipe down and large-surface disinfection. Likewise, high-moisture alcohols evaporate slower and increase contact time without becoming immediately dry. If 70% IPA is so effective as both a general-purpose cleaner and disinfectant, why use 99% concentrations?

When Is 99% Isopropyl Alcohol Used?

99% isopropyl alcohol is ideal as a solvent or cleaning agent for industries that produce water sensitive items, therefore rapid evaporation and low water content is favorable. 99% IPA provides the lowest presence of adulterants and is free from denaturants. Computer technicians, medical device manufacturers, printed circuit board manufacturers, and soldering and rework technicians prefer immediate evaporation for work with sensitive devices such as integrated circuit adapters, computer chips, and circuit boards. 99% IPA evaporates cleanly, and minimizes residual substances. Rapid evaporation reduces shelf life, but ensures unchanging alcohol concentration. Alcohol evaporates faster than water when exposed to air; over time the alcohol concentration is diluted by excess water which yields unpredictable effectiveness and results. This degradation is avoided with pure isopropyl alcohol. It’s more effective against sticky residues, grease, and grime than 70% concentrations, but because isopropanol is hydroscopic, acetone may yield better grime fighting results.

What’s the Difference Between Types of Isopropyl Alcohol?

What Is USP-Grade Isopropyl and What Is It Used For?

The United State Pharmacopeial Convention (USP) is a nonprofit scientific organization that develops and disseminates public quality standards for medicines, food, and supplements. USP-grade certification ensures that both the isopropyl alcohol and any additives are of the highest purity, potency, and accurate concentration. Manufacturing, packaging, and storage must adhere to strict guidelines, and all production facilities must uphold FDA registration and inspection. These specifications improve consistency and safety for industrial, pharmaceutical, flavor & fragrance, or lab use.

What Is Pure Isopropyl Alcohol?

Pure isopropyl alcohol is manufactured and processed without common additives such as denaturants, which discourage human consumption. Pure isopropyl alcohol is not interchangeable with sterile or USP-grade isopropyl alcohol, but misnomers occur frequently because USP-grade alcohol is always in a pure state.

What Is Industrial Grade Alcohol?

Industrial grade isopropyl alcohol is used most commonly for non-critical manufacturing and processing purposes such as removing ionic salts from PCBs, thermal paste from heatsinks and IC packages, or dissolving the organic acids in rosin-based soldering fluxes. It’s an economic option for disinfection of large surface areas, and mitigation of general contaminants such as dust, debris, grease, and adhesives present from other manufacturing processes.

What Is Sterile Isopropyl Alcohol?


Sterile Isopropyl Alcohol meets the highest standards of purity in aseptic environments. Sterile certification ascertains 0.22-micron filtering, gamma irradiation between 25kGy – 50kGy and compliance of modified AAMI/ANSI/ISO 11137:2006 guidelines. Sterile IPA is packaged in a cleanroom and commonly used within the same environment for wipe down of pass-throughs, cleanroom furniture, laminar flow hoods, cleanroom furniture, and tables or work surfaces.

Is Isopropyl Alcohol the Same as Rubbing Alcohol?

Rubbing alcohol is a antiseptic which U.S. Pharmacopeia standards defines as containing not less than 68% and not more than 72% of isopropyl alcohol, by volume, the remainder consisting of water, with or without suitable stabilizers, perfume oils, and color additives certified by the FDA for use in drugs. The difference between rubbing alcohol and more pure forms, is that rubbing alcohol contains denaturants which make the solution unpalatable for human consumption. Technically, all grades of rubbing alcohol containing 68% -72% isopropyl alcohol fall under the “rubbing alcohol” namesake for household use. Isopropyl alcohol concentrations >91% volume fail to provide bactericidal efficiency and are less effective for antiseptic use, thus its distinction as “rubbing alcohol” is not warranted and may cause confusion.

For more information, continue with suggested reading below, or contact us about ordering in bulk, hazmat requirements, or for further questions on best usage and results.

Additional sources:




Leave a Reply

Please log in using one of these methods to post your comment:

WordPress.com Logo

You are commenting using your WordPress.com account. Log Out / Change )

Twitter picture

You are commenting using your Twitter account. Log Out / Change )

Facebook photo

You are commenting using your Facebook account. Log Out / Change )

Google+ photo

You are commenting using your Google+ account. Log Out / Change )

Connecting to %s

Create a website or blog at WordPress.com

Up ↑

%d bloggers like this: