Keeping the tiger in your tank – not on your hands!
The FDA has acknowledged that there has been a recent increase in methanol contamination in alcohol-based hand sanitizers. Methanol, also known as Carbinol, Methyl Alcohol or Wood Alcohol is an additive that is commonly used in gasoline and even a component in rocket fuel! Basically, there are 2 main ways for Methanol to find its way into hand sanitizing products:
- As a byproduct of Ethanol when Ethanol is used as one of the main ingredients to produce a hand sanitizing product.
- Or if Methanol as an ingredient was deliberately introduced during the production of a hand sanitizer product.
Methanol is poisonous and potentially deadly and should never be deliberately introduced as an ingredient in the production of hand sanitizers. However, its inclusion can occur when manufacturers unknowingly purchase an inappropriate alcohol raw material; whether the alcohol is contaminated or the wrong type, either could compromise the integrity of the hand sanitizer and result in methanol contamination. Conversely, Ethyl alcohol or Ethanol is widely accepted as a safe and potent virucidal ingredient in hand sanitizers. In fact, the only alcohols that should be used for hand sanitizers are Ethyl alcohol and Isopropyl alcohol. What follows are some definitions and key considerations for properly testing hand sanitizers for the presence of Methanol.
What concentration of alcohol should be used?
70% concentrations of either ethanol or isopropyl alcohol has been demonstrated to be the most effective. Water acts as a catalyst and plays a key role in denaturing the proteins of vegetative cell membranes. The water content slows evaporation, therefore increasing surface contact time and enhancing effectiveness. At concentrations higher than 80-85% the effectiveness of a sanitizer as a disinfectant decrease.
Is it effective to use ethanol or isopropyl alcohol as a disinfectant?
–Ethyl alcohol (ethanol), at concentrations of 60%–80%, is a potent virucidal agent inactivating all of the enveloped viruses (e.g., herpes, vaccinia, and influenza virus) and many nonenveloped viruses (e.g., adenovirus, enterovirus, rhinovirus, and rotaviruses but not hepatitis A virus (HAV) or poliovirus). It has also been demonstrated to be effective against human immunodeficiency virus (HIV), rotavirus, echovirus, and astrovirus. -Isopropyl alcohol, based on some studies, at concentrations of 60%-80% is not as active against the nonenveloped enteroviruses but is fully active against the enveloped viruses. Studies also have demonstrated the ability of both ethyl and isopropyl alcohol to inactivate the hepatitis B virus (HBV) and the herpes virus. Sars CoV2 is an enveloped virus.
Enveloped vs. nonenveloped viruses
A virus encased within a lipid bilayer is called an enveloped virus. On the other hand, a virus lacking a lipid bilayer is called a non-enveloped virus. The distinction is important because the additional bilayer is readily denatured by alcohol, making enveloped viruses more susceptible to hand sanitizers than nonenveloped viruses.
What amount of contact time should be used?
The concentration of ethanol or isopropyl alcohol determines the amount of contact time needed; the higher the concentration (>70%) the longer the contact time required for disinfection. Recommending at least 2-10 minutes of contact time for 70% concentration and 5- 15 minutes if using greater concentrations of alcohol are used (not to exceed 80%).
Purity of Ingredients:
Strength of Ethyl alcohol Should be determined by compendial methods before it goes into the final product. Also, the impurities in the Ethanol should be accounted for to have confidence in the raw material. Main impurity of Ethanol is Methanol for raw material it should be NMT 200ppm or 200µl/liter.
Strength of Isopropyl alcohol should be determined by compendial methods. Also, organic impurities should be accounted for as part of test.
Most common excipients are Glycerin, Vitamin E (Alpha tocopheryl acetate), Carbomer and the most importantly Water.
Glycerin: The limit of Ethylene glycol and Diethylene glycol should be accounted for during testing.
Carbomer: This excipient works as thickening agent in the hand sanitizer. There are different grades of the carbomer available. Each carbomer should be tested for the residual solvents. Depending on the grade most common residual solvents are Ethyl acetate, Cyclohexane, Benzene and Acrylic acid.
Vitamin E: Strength of Vitamin E is optional.
Water: The Water used in final product should be sterile water. pH, TOC, Conductivity or Resistivity and microbiology testing should be performed prior to manufacturing the final product.
Final product should be tested for Strength of alcohol for effectiveness of the sanitizer.
Assay for Alcohol: (V/V %) in final product.
These are still open to debate but following table from the CDC can provide some guidance:
|10 min||30 min||60 min||4 hr.||8 hr.|
(discomfort, non-disabling) – ppm
|670 ppm||670 ppm||530 ppm||340 ppm||270 ppm|
(irreversible or other serious, long-lasting effects or impaired ability to escape) – ppm
|11,000 ppm||4,000 ppm||2,100 ppm||730 ppm||520 ppm|
(life-threatening effects or death) – ppm
|**||14,000 ppm*||7,200 ppm*||2,400 ppm||1,600 ppm|
The limit of methanol in hand sanitizers is the most important consideration when it comes to choosing the safest sanitizing product. Hand sanitizers will be effective and safe if the raw materials (ingredients) have been properly tested for impurities. But it is always recommended that samples of the actual finished product be tested as well. Intentional or unintentional introduction of methanol in the hand sanitizers could have devastating effects ranging from simple discomfort to potentially becoming deadly.
About the author:
Maussamkumar Patel is a Chemistry Supervisor at NJ Labs. He is an expert in GC and HPLC analysis with emphasis on method development and validation experience. He brings over 8 years of analytical chemistry experience in dietary supplements and pharmaceutical products to NJ Labs. Noteworthy in Maussamkumar’ s background is his recent method development and validation in accurately quantifying Alcohol content and methanol in Alcohol‐based sanitizers. He holds a BS degree from Saurashtra University in India.