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Glycolic acid reacting with peservative
HI , so I have a little problem. I was formulating a 7 % AHA serum and when I added the preservative (benzyl alcohol, dehydroacetic acid, aqua) at pH around 4 it precipitated forming a viscous yellowish substance at the bottom.I thought that maybe the glycolic acid reacted with the benzyl alcohol forming an ester or maybe the dehydroacetic acid became instable or something.
Note : When I usually formulate emulsions even at pH 4 it doesn’t precipitate, it happen just with this kind of serums that include acids
Can you please explain to me what happened if you have any idea and what preservative do you recommend for this type of formula?! Thank you in advance.
formula:
Water
glycolic acid
lactic acid
Glycerin
xanthan gum
Sodium Hydroxide
Preservative ( 1% )
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6 Replies
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It’s associated with the addition of which preservative?
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It’s Cosgard which is a combination of benzyl alcohol and dehydroacetic acid and water
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It’s not that great a system anyway. Why not try something more pedestrian like benzoate/phenoxy.
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What percentage do you recommande using when combining both preservatives and is phenoxyethaol suitable for water based formulas ?
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Should be ok. ~ 0.5% (5000 ppm) phenoxy and 0.3% Na benzoate.
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Ok, I will try to switch the preservative and see if the problem is solved. Thank you very much for your help !!
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