Isopropyl Alcohol: 70% versus 99%
In the typical craft beverage laboratory setting, isopropyl alcohol (IPA) is used to eliminate microbes (molds, bacteria, and yeast) so they do not contaminate the samples being collected or processed and, in turn, adversly impact the reliability of the tests being performed.
When deciding which concentration of isopropyl alcohol (IPA) to use for disinfecting surfaces and sterilizing equipment in a craft beverage laboratory setting, the question natually arises whether 99% is “better” than 70%.
Using 70% alcohol is generally recommended for a few key reasons:
- A 70% solution penetrates the cell wall more completely, thereby killing the microorganism by denaturing and coagulating proteins in the cell membrane
- The 30% concentration of water slows evaporation, increasing surface contact time
- It produces less vapor and odor than higher concentrations, reducing the risk of toxic fumes or combustion
Should it, however, be more convenient to procure 99% IPA, use the table below and a graduated cylinder to make a 70% solution from a mixture of 99% alcohol and distilled water.
|Target Volume||Target Concentration||Volume of 99% IPA||Volume of Distilled Water|
|1000 ml||70% (.70)||700 ml||300 ml|
|500 ml||70% (.70)||350 ml||150 ml|
|450 ml||70% (.70)||315 ml||135 ml|
SAFETY NOTE: In order to protect skin, eyes, and other vulnerable mucuous membranes, always wear appropriate personal protective equipment (PPE) when mixing chemicals.
Also, remember to add the correct volume of distilled water into the cylinder first, then pour the alcohol into the water. Following this sequence minimizes the likelihood that alcohol will be displaced from the cylinder should any splashing occur.
Isopropyl alcohol is highly flammable and can easily ignite. It should be kept away from heat, sparks, flames, and other sources of ignition. A flammable safety cabinet is a good storage option.
Consult the manufacturer’s Safety Data Sheet in order to become familiar with all the hazards of any particular IPA product.
Spray and Wash Bottles
For convenient use when disinfecting a work area or preparing a piece of equipment to be sterilized, working concentrations of IPA should be stored in appropriate containers, either spray bottles or wash bottles made of a material suited to the nature of the chemical.
When selecting a container, it is essential to check the compatibility between various materials, including plastics, and chemicals such as isopropyl alcohol.
Chemicals removed from their original containers and placed in spray or wash bottles must be labelled in accordance workplace safety rules, such as those spelled out by OSHA (Occupational Safety and Health Administration).
This OSHA document addresses the labelling rules pertaining to secondary containers, also known as workplace containers. Consult you own country’s rules if your buisness is located outside OSHA’s jurisdiction.
Before placing any label into service, confirm that it meets all relevant requirements related for the situation in which it will be used.
Here are some labels that meet current OSHA standards (as of March 2021).
Label source: https://www.mysafetylabels.com/isopropanol-labels
NOTE: Chemicals such as isopropyl alcohol can have a variety of names for the same substance. PubChem is a reputable source for cross-referencing such synonyms.
The National Institute for Occupational Safety and Health (NIOSH) Pocket Guide to Chemical Hazards has additional safety information about isopropyl alcohol.
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