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Niacinamide hydrolyzing while making a lotion?
I made a 5% niacinamide lotion the other day. From what I have read, the final pH of the lotion should be around 6 so that the niacinamide does not undergo hydrolysis. I had weighed out my ingredients the night before (into sterile glass jars), then I thought, while trying to sleep, that perhaps my niacinamide was hydrolyzing in the water phase.
I checked the pH of the water phase before I began the heating & holding the next day, and it was around 5.5. I decided to proceed with the lotion without increasing the pH at this point because this is the first time I made this lotion and I have no idea how crucial, if it is, to have the pH exactly at 6.Is it possible my niacinamide WAS hydrolyzed, while I dreamt of sugar plums & fairies?
Here is my water phase:
EDTA 0.2%Water 63%Propylene Glycol 5%DL Panthenol (powder form) 5%Sodium Lactate 2.5%Niacinamide 5%When I added the oils phases to the water phase (containing the niacinamide), the pH was 4.5, so I increased it to 6 with triethanolamine before adding the preservative & scent, when it cooled down enough.Thank you! -
4 Replies
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Digging from my deepest chemistry memories, I think it is best to add a pre-dissolved Niacinamide into the lotion after adjusting the pH of your base to 6 and above.
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since you’ve got no strong acids or strong bases in the formula, the chance of hydrolysing the nicotinamide (or any amide, for that matter) is low
this page describes the general process of amide hydrolysis -
@Margreat:
Since you have Sodium Lactate in your base formula, no need to then add Triethanolamine to increase your pH … just add more Sodium Lactate. -
I can’t find my source for this at the moment, but I believe that the hydrolysis reaction of nicotinamide has such a slow rate between pH 4-6 that it should be fine when one considers how long the product will take to use up, shelf life, etc.
Also, as said by Bill_Toge, there are no strong acids or bases present.
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