Sodium Ascorbyl Phosphate

Hi everyone,

I'm new here to posting, but have been a lurker for years, so hello!  I've searched multiple times on this forum but haven't arrived at a conclusion and hoping someone can offer some advice.  I'm the formulating chemist for a small cosmetic manufacturer, been formulating for roughly 6ish years but have zero experience on formulating vitamin C products.  

We had a 20% ascorbic acid serum that was made by another manufacturer that we were going to try and make ourselves to save some money.  We decided to switch to sodium ascorbyl phosphate because one of our customers wanted to formulate a new product with it, and since we'd be purchasing the raw material, we decided to re-create our serum with SAP.  We did a 20% serum and then another 3% serum for our customer.  No matter what we've tried, both serums turn brown and we're getting complaints.  I understand that all vitamin C is unstable, but from what I've read online, SAP is supposed to be "more stable".  I also understand 20% is a LOT to use; we're trying to stick with our "claims" and current INCI, hence the added fluff in the formula.  I've kept the pH above 6 based on literature I've read as well. 

Here is our formula:

Witch hazel water - 40%
Water - 21.48%
Disodium EDTA - 0.1%
Xanthan Gum - 0.4%
Glycerin - 15%
Green Tea Extract - 0.01%
Grape Seed Extract - 0.01%
SAP - 20%
Glucosamine HCl - 0.5%
Tocopherol - 1%
Ferulic Acid - 0.5%
Euxyl PE 9010 (phenoxyethanol, ethylhexylglycerin) - 1%

Our customer formula is similar, but with [Polyacrylamide, C13-14 Isoparaffin, Laureth-7] and 3% SAP.  In the oven after a week, it did not turn brown, but our batch from January is being returned because it "looks like rust".  

Does anyone have any suggestions on how to make these more stable, or am I SOL?  Thanks so much in advance!


  • PharmaPharma Member, Pharmacist
    The higher your %, the stronger degradation and the better visible degradation becomes (-> 1% of 1% is close to nothing, 1% of 20% is clearly visible). You could try to increase pH to 7 (including a buffer might help), add a bit more EDTA (0.2%) and also include a water soluble antioxidant (ferulic acid might work or might not and I don't know how you manage to dissolve 1% tocopherol.... do the 15% glycerol suffice?) Anyway, phenolics don't regenerate ascorbic acid -> thiosulfate or metabisulfit would do and also neutralise dissolved oxygen (or flush with nitrogen, at least boil your water to degas it).
    Plus, don't work with metal containing materials (at least pacify these).
  • Bill_TogeBill_Toge Member, Professional Chemist
    edited September 2020
    +1 for bisulphite
    also you may want to consider adding an excited-state quencher, e.g. benzophenone-4 or Tinogard Q, that will keep the concentration of reactive radicals, e.g. oxygen, to a minimum
    UK based formulation chemist. Strongest subjects: hair styling, hair bleaches, hair dyes (oxidative and non-oxidative) I know some stuff about: EU regulations, emulsions (O/W and W/O), toothpaste, mouthwash, shampoos, other toiletries
  • sean9980sean9980 Member
    edited September 2020
    You need some polysorbate 20 in there if your going to include oils in it tmk, your also not going to put in 20% SAP, thats a bit too much and would prolly cause a lot of irritation, I think max usage is around 8%, the claims online has to do with the (20% Vitamin C bioavailability), SAP is pretty expensive if your buying it from the usa, but pretty cheap, or reasonably cheap from china. Also your batches shouldnt be turning brown, they prolly cheaped out on you and put regular vitamin c in there lol, feurlic acid i think has some sort of patent on it with the regular l-ascorbic acid as it prevents it from breaking down quickly, ive read up on it and i am also planning a vitamin c for commercial distribution

    "The present invention relates to single-phase solution compositions of L-ascorbic acid that provide enhanced stability, enhanced solubility and an enhanced photoprotective effect as compared to prior compositions. The single-phase solution compositions comprise by weight 5% to 40% L-ascorbic acid; 0.2% to 5.0% of a cinnamic acid derivative, such as p-coumaric acid, ferulic acid, caffeic acid, sinapinic acid, a derivative thereof, or a combination thereof; 10% to 60% of a solvent comprising a glycol ether and an alkanediol; and water; the composition having a pH of no more than about 3.5. When the cinnamic acid derivative is present at an amount greater than 0.5%, the composition further comprises a surfactant in an amount of 1.5% to 5.0%. The single-phase solution compositions may also comprise a form of Vitamin E and a surfactant, or a form of Vitamin A and a surfactant."

    As you can see its a bit of restricted technology, in that case, anyhow good luck
  • sean9980sean9980 Member
    edited September 2020
    A combination of 0.5% ferulic acid (a potent antioxidant of plant origin) with 15% Vit. C and 1% Vit. E can increase the efficacy of Vit. C eight-fold.[3] It was noted that this triple combination was very useful for the reduction of acute and chronic photodamage, and could be used for prevention of skin cancer in the future.


    "Because this form of Vitamin C is easily absorbed and utilized by the skin, it is not associated with the irritation often experienced with L-ascorbic acid. ... We use about 10% sodium ascorbyl phosphate which is equivalent to a much higher concentration of L-ascorbic acid because it is much more bioavailable."
  • Thank you SO much everyone for your responses.. I am definitely going to reformulate now.  Appreciate all the help!
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