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Antibacterial activity of liquid hand soap
After many trials and error, and comparing to other brands. i found this hand soap formula is quiet good. The foam is stable, moist, and easy to be rid off. Here is the formula i use per 100ml:
SLES 70% 9.5 gr
CAPB 2.5 ml
NaCl 2.7 gr
Glycol Distearate 1 ml
Polyquaternium-7 0.7 ml
Sodium Benzoate 0.7 gr
Parfume 0.7 ml
Gliserin 0.5 gr
Citric Acid 0.3 gr
EDTA 2Na 0.2 gr
Phenoxyethanol 0.1 ml
Aloe extract 0.1 ml
Benzalkonium Chloride 0.1%
(All the substance amount is fit to the national regulation)But, after i run a antimicrobial activity analysis using EN1040:2005 method, the result is not good enough.It only shows 75,238% antibacterial activity for E.coli & 82% for S.aureus with 5mins contact time.And the result should be 100% after 5 mins to pass this test (CMIIW)The question is, what can go wrong with my formula that affect antimicrobial activity of the soap? Is there any substance that counteract the antimicrobial activity?
what can i do to get a higher result without change the contact time?or is the result is acceptable for liquid hand soap?
Thank you in advance. -
7 Replies
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@vandrean Not only the amount of Benzalkonium chloride (BC) is a bit low (you can try at least doubling it, assuming you’re using an 80% BC), the manufacturers state that BC shouldn’t be use with anionic surfactants, not only because of imcompatibility issues, but because of that, BC will be “kidnaped” by the anionic, without being able to perform.
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BC performance can be affected or even dont work at all if you mix it with other surfactants
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ketchito said:@vandrean Not only the amount of Benzalkonium chloride (BC) is a bit low (you can try at least doubling it, assuming you’re using an 80% BC), the manufacturers state that BC shouldn’t be use with anionic surfactants, not only because of imcompatibility issues, but because of that, BC will be “kidnaped” by the anionic, without being able to perform.natiyo123 said:BC performance can be affected or even dont work at all if you mix it with other surfactants
Oh well, I will eliminate the BC then..
I also tested the other liquid soap that contain no BC with the ingredients below:aqua
sles 4.28%
capb 2.9%
lactic acid,
sodium chloride
sodium benzoate
polyquat-7
glycerin
tetrasodium glutmatae diacetate
benzotriazolyl dodecyl p-cresol
parfume
mel ~ (and i wonder what is this? 🤔)
pottasium sorbateAnd even wihtout BC and smaller conc. of sles, it shows 3 times higher result (71% at 20s for E.coli), where mine is only shows 26% at 20s.
And because the BC doesn’t work, what can i do to improve the antimicrobial activity? (At least close to the other product) -
@vandrean Sodium benzoate has a fair antibacterial activity, also the low pH could also play a role (depending how diluted was the sample for the test). And last but not least, the amount of SLES is higher (surfactants also have antimicrobial activity).
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Benzalkonium chloride is cationic and is not compatible with anionic surfactants such as SLES. You need to use non-ionic or cationic ingredients only. If you eliminate the Benzalkonium chloride you will not have an antibacterial hand cleanser as you are removing the main active ingredient.Lactic acid can also be used as an antibacterial active and is probably what is giving the better result in the other sample you tested.Mel = honeyThere are a number of antibacterial hand wash formulations on UL Prospector that are good starting points. -
ozgirl said:Benzalkonium chloride is cationic and is not compatible with anionic surfactants such as SLES. You need to use non-ionic or cationic ingredients only. If you eliminate the Benzalkonium chloride you will not have an antibacterial hand cleanser as you are removing the main active ingredient.
The same seems to be true for the ‘go to’ antibacterial compounds. I read the same for chlorhexidine digluconate yesterday, as it happens.
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Sodium Benzoate 0.7 gr
Benzalkonium Chloride 0.1%
seem like preservatives amount. - I think it would take hrs to pass 3log.
is the result is acceptable for liquid hand soap? if you don’t claim Antibacterial i guess yes?
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