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Sanitizer Formulation (Comments & Suggestions Please)
Dumb
MechE here whose learned formulating basics from formulating water-based
adhesive for tissue/towel market (i.e. glue holding last sheet of the roll down).
Looking for comments / suggestions on hand sanitizer formulation to help fight
COVID-19 pandemic. Spray formula listed below (still working on gel):76. %
Isopropyl Alcohol (99%)2.5% D - Sorbitol
[Humectant 01]0.20%
Sodium PCA – Ajidew NL-50 [Humectant 02]0.30% Glucam
P-20 (PPG-20 Methyl Glucose Ether) [Humectant 03]1.5%
Isopropyl Myristate [Emollient]0.15% Tocopheryl
Acetate [Skin Conditioner: Vitamin E]0.15% Potassium
Sorbate [Preservative]q.s. to
100 = H2O: Distilled WaterNOTE:
Opted to NOT use glycerin as humectant. We use Glycerin Kosher 99.7% in our
transfer glues (adhesive applied to the brown core designed to grab 1st
sheet of paper towel/toilet paper during mfg process) and I DON NOT like the
stickiness feeling. Went with a skin moisturizing humectant package instead.Reviewed
basic patent information & discussion post comments (thank you @Perry,
@Pharma, @em88, @Belassi to name a few) for guidance. I think it’s a solid
formula but will test this and other options once our lab opens back up. Please
educate me if I’m heading down the wrong path. -
9 Replies
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Also, I left out a fragrance as I wanted product to be “unscented”.
Should I add? If so, anything other than essential oil recommended to
test? -
“Also, I left out a fragrance as I wanted product to be “unscented”. Should I add? If so, anything other than essential oil recommended to test?”
- Hospital sanitisers are usually unfragranced, ones you find in stores may or may not have fragrance. My own thoughts as follows:
1. Fragrance oil. I cannot see this adding to or even maintaining the antiviral efficacy, so, no.
2. EO. Many EOs eg Lavender, Tea Tree, have antibacterial effects at an MIC around 0.1%. I’m using DI water to hydrate the carbomer so I think spores are not a problem. For my family and friends I formulated initially with 0.1% of lavender oil, primarily for fragrance. This proved too much; now, I use 0.05% lavender oil.
3. As noted by others (@Perry) you can use 1.1% Benzalkonium chloride, a cationic antiseptic, as a useful inclusion and that would allow the use of unpurified water (e.g. as a field prep)
4. 70% V/V alcohol is generally available but it’s a lot more difficult to obtain higher percentages, and such are more dangerous to handle, too. I found it not difficult to prepare a 63% V/V ethanol gel using 70% V/V ethanol, 940 carbomer neutralised with TEA. Not quite as crystal clear as Ultrez 21 but pretty good nevertheless. -
I like sorbitol and PCA, way nicer feeling than glycerol. How they will affect antimicrobial efficacy remains to be tested.IPM is also nice and, like Glucam P-20, might actually boost antiviral activity (sorbitol and PCA might however reduce it). But this is only an educated guess!Ditch the sorbate, it’s useless (you have a hand sanitiser and if that one needs preservation, you’re doing it wrong :smiley: ). Also ditch toco, it’s useless and adds uncertainty.If you want to give your product an additional edge, lower pH somewhat below skin pH. -
You should keep the formulation as simple as possible unless you test your formulation efficacy. What’s the preservative doing there? Tocopheryl is not needed. I think that 0.20% Sodium PCA and 0.30% Glucam P-20 are very low to actually have a noticeable effect.
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em88 said:…I think that 0.20% Sodium PCA and 0.30% Glucam P-20 are very low to actually have a noticeable effect.Not necessarily. Don’t forget that the alcohol evaporates fast and hands are treated several time a day. This means that the total amount deposited on skin per day might be more important than the actual % added to the sanitiser.Whether or not a noticeable effect is needed is questionable since proper usage would not rise the demand for a humectant in the first place. Regularly applying hand or barrier creams would be a more efficient way for people abusing or badly using hand sanitisers.
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Pharma said:em88 said:…I think that 0.20% Sodium PCA and 0.30% Glucam P-20 are very low to actually have a noticeable effect.Regularly applying hand or barrier creams would be a more efficient way for people abusing or badly using hand sanitisers.
Exactly! People will wash their hands often anyway. In my opinion, there is no real reason to insist so much on adding humectants/emollients in sanitizer preparations. I’d use propylene glycol or 1,3 - propanediol and that would be enough.
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em88 said:(…) What’s the preservative doing there? (…)
Below what concentration of alcohols, ethyl or IPA (as sole disinfecting agent), would you recommend a preservative in hand sanitizers, by the way?
Aren’t alcohols relatively weak on mold/yeast? If so, I would understand the addition of potassium sorbate. -
Potassium sorbate won’t work at the sanitiser pH and would discolour it, also.
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Doreen said:Aren’t alcohols relatively weak on mold/yeast?The formulation of @RE50 contains 75% IPA and that is more than any mould/yeast can take. Relatively means that they grow at ethanol % up to wine strength (max. ~15%), killing starts later.I can imagine that, at an alcohol concentration sufficient to stop microbes from growing, weak acid preservatives greatly lose efficacy because you can not disturb a metabolic process which, at that moment, doesn’t take place.
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