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Vit C, MAP to be exact, and formulation pH
Hello. I recently asked some questions about pH drift and my preservative gluconolactone and SB and skin sensitivity. Thanks to input from your site, I will now be switching to a different preservative and just trying gluconolactone by itself.
However, I had wanted to try some magnesium ascorbyl phosphate in my lotion as I used to use AA, but my skin has become too sensitive for that. (as background, I only formulate for me in small batches, so this isn’t for resale). My skin did seem to like vit C (AA), before it became more sensitive (maybe tmi, but I’m blaming hormones), so I’m trying to find a Vit C alternative. I welcome all suggestions on whether I am even wasting my time or money with MAP. I just that I had researched it was the better option for people with more sensitive skin. (hence also why I’m trying gluconolactone, because I can’t seem to used AHA’s anymore either).
But I have read in the product info that MAP may discolor at a pH below 6. If my end product ends up being closer to pH 5, does that mean it (MAP) will not be effective at all, or just have a potential color problem? I’m not worried about color, just effectiveness.
Maybe I should use the MAP and gluconolactone in separate lotions if the pH could be a problem…?
Thanks in advance for any help. Your site is awesome and as the simple home user, I truly appreciate all your big gun professional help. I know I’m no chemist, despite researching things to death.
Kim -
5 Replies
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I use a rather different type of vitamin C, Apprecier, from Showa Denko. Generally speaking, yellow = oxidised
and degraded. I am adopting an airless container for this product and we recommend keeping it in the refrigerator.
You need to be very careful when formulating with vitamin C. Too high or too low a pH at some point, or the wrong temperature, and it’s gone. Activity declines as a straight line from manufacture, so you want to make small batches. -
@Belassi… Righteo. I wondered if it was enough to change the color that most likely meant some amount of oxidation and therefore less effective at that point. Thanks for your reply. I figure I will stick to the pH the product recommends and just make separate lotions for different things. And yes, I always make smaller batches and keep mostly refrigerated.
Can’t always use the kitchen sink approach for everything even if it would be easier, I suppose, ha!
Thanks again. -
If you want to use a vitamin C compound effectively, you should closely follow the supplier’s recommendations. In my case, Showa Denko provide several example formulations and these relate to the product lifetime versus certain criteria.
The criteria are mainly solvents in the formula. I guess if you’re in the USA then it may be easy enough to obtain the specialised solvents that inhibit oxidation. Propylene glycol for instance is the reference (but isn’t great) and glycerol is useless. So unless you’re into 2,4-6 propenadiol, etc, vitamin C is a challenging active to formulate with.
In my case, the testers are so in love with the product that I have decided to continue working with it even though I am having the hassle of sourcing new airless packaging, boxes for the package, print a product leaflet to go inside the box, work with small batches and refrigerate at point of sale, etc.
It really is that good. But yellow … well they say, don’t eat the yellow snow. -
MAP is most stable at pH 6.0. You may experience more rapid oxidation at MAP at a pH of 5.0 than at 6.0. As with any Vitamin C or derivative, they will oxidize/discolor at any pH over time. It’s more a matter of just how quickly the MAP oxidizes, not a question of whether or not it will oxidize … it will under any condition, just more rapidly under certain conditions than others.
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Thanks to you both @Belassi and @MarkBroussard…
Yup. Vit C is a bit of the pain in the patootie. But I’ll give it a whirl for myself in small, frequent batches and at the proper pH (as best as possible ) and see if my skin has anything positive to say about it
. Thanks again for all your help!
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