Home Cosmetic Science Talk Formulating Preserving a low pH serum

  • Preserving a low pH serum

    Posted by DIY_Newbie on September 17, 2019 at 2:41 am

    Hello all,

    This is a follow up post from June.  I’m attempting to create a vitamin C serum for skin lightening (personal use).  I have revised my formula to the ingredients below.  I would use a paraben as a preservative (Paraben DU or Germaben II) but the surfactants I’m using are non ionic and will inactive parabens from my understanding.  Is there any other options for me? Can I still use a paraben preservative system?  Would this be preserved enough for 3ish months of use by itself(just Potassium Sorbate)?  I’m trying to find something user friendly (simple to mix in) if possible.

    Ingredients Percentage
    Distilled Water 56
    L-Ascorbic Acid 17
    Poly Suga Mulse D9 4
    d-alpha-tocopherol 1
    Propanediol 1,3 15
    Ferulic Acid 1
    Sodium Gluconate 0.6
    Sodium Lactate 4.0
    Glucono Delta Lactone 0.6
    Citric Acid 0.3
    Potasium Sorbate 0.5

    Any other feedback is also appreciated.

    Thank you for reading.

    DIY_Newbie replied 4 years, 6 months ago 4 Members · 9 Replies
  • 9 Replies
  • ngarayeva001

    Member
    September 17, 2019 at 2:45 pm

    I understand that some chemists might throug rotten tomatoes at me for saying it, but your formula is self preserving though… Look you have 15% of glycols (which means water activity is very low), you have a chelator, it’s low pH because I can see 17% of LAA plus citric acid.. is it around 2? I don’t see any bug food either.. You should be fine for 3 months with Germaben II or without.

    To be honest it’s such a nice formula for someone with a name @DIY_Newbie :)
    Every time when I hear “DIY” I think of “goat milk, PEGs are toxic, organic raw honey, parabens cause cancer” kinda crowd. Well done :)

  • ngarayeva001

    Member
    September 17, 2019 at 2:48 pm

    I have to dissapoint you just a little bit. Vitamin C doesn’t do much for skin lightening unfortunately. But you can only figure this out yourself. By the way, I will stain your pillow case, so be aware of that if you apply it at night.

  • pharma

    Member
    September 17, 2019 at 7:19 pm

    … I would use a paraben as a preservative (Paraben DU or Germaben II) but the surfactants I’m using are non ionic and will inactive parabens from my understanding.  Is there any other options for me? Can I still use a paraben preservative system?  Would this be preserved enough for 3ish months of use by itself(just Potassium Sorbate)?…

    As @ngarayeva001 said, 15% 1,3-propanediol is already self-preserving plus a very low pH, gluconolactone, gluconate, and citric acid (why use all three? Gluconolactone builds gluconate and that one does about the same than citric acid ;) ), the rest is antioxidants. That cocktail is pure preservation :smiley: !
    Honestly, I don’t think that you’d even have to add sorbate or the like. If you want something to be on the super-safe side, go with a slightly volatile preservative to protect also head space. 2-Phenylethanol aka phenethyl alcohol but also anisic acid (not sure if pH well below 4 is okay for anisic acid) would come to mind. Sorbate is a good choice for low pH and low water activity products such as your serum since the main problematic microbes are yeasts and moulds but not bacteria.
    Regarding non-ionics inhibiting parabens: This is based on findings with PEGs. I haven’t heard of parabens being inactivated by polyols (e.g. Suga Muls).
    I would bet that your product spoils first on a chemical level (ascorbic acid degradation/oxidation) than a microbial one. 3 month for an aqueous DIY solution such as yours should be more than fine!
  • ngarayeva001

    Member
    September 17, 2019 at 8:25 pm

    I wonder how serious is it about PEGs. I saw so many commercial products with PEGs preserved with parabens.. maybe it’s only relevant for very high amounts of PEGs?

  • markbroussard

    Member
    September 17, 2019 at 9:48 pm

    @DIY_Newbie

    You might be better off just using Gluconlactone, Sodium Benzoate, Calcium Gluconate … Geoguard Ultra or Gluconlactone SB instead of the individual ingredients … it’s a pre-mix preservative blend.  One ingredient instead of 3 separate ingredients.

  • DIY_Newbie

    Member
    September 18, 2019 at 2:09 am

    Thank you all for your comments.

    ngarayeva001
    Pharma
    MarkBroussard

    Pharma said:

    … I would use a paraben as a preservative (Paraben DU or Germaben II) but the surfactants I’m using are non ionic and will inactive parabens from my understanding.  Is there any other options for me? Can I still use a paraben preservative system?  Would this be preserved enough for 3ish months of use by itself(just Potassium Sorbate)?…

    As @ngarayeva001 said, 15% 1,3-propanediol is already self-preserving plus a very low pH, gluconolactone, gluconate, and citric acid (why use all three? Gluconolactone builds gluconate and that one does about the same than citric acid ;) ), the rest is antioxidants. That cocktail is pure preservation :smiley: !

    I was intending to make sure I had no issues with preservation of the serum so I went a little overboard on the chelators.  The sodium lactate is something I would like to keep at 4-6 percent though.  The pH is desired to be around 2.7-3.0 (my face can handle low pH products without issue).  Of the 3 which ones would you prefer would stay in and at what concentration?  I will use sodium hydroxide to raise the pH up if its to low (below 2.5).  

    Pharma said:

     If you want something to be on the super-safe side, go with a slightly volatile preservative to protect also head space. 2-Phenylethanol aka phenethyl alcohol but also anisic acid (not sure if pH well below 4 is okay for anisic acid) would come to mind. Sorbate is a good choice for low pH and low water activity products such as your serum since the main problematic microbes are yeasts and moulds but not bacteria.

    What do you mean by “head space”.  Just want to make sure confusing this with something else.

    @DIY_Newbie

    You might be better off just using Gluconlactone, Sodium Benzoate, Calcium Gluconate … Geoguard Ultra or Gluconlactone SB instead of the individual ingredients … it’s a pre-mix preservative blend.  One ingredient instead of 3 separate ingredients.

    I do have Gluconolactone SB (NeoDefend is what is was called when I bought it) on hand by I saw a disclaimer mentioning that the Sodium Bezonate can be converted into Benzoate. 

    This is from Lotioncrafters:

    There is some concern that  Sodium Benzoate, one of the ingredients in NeoDefend, in combination with L-Ascorbic Acid in products can form Benzene, a known human carcinogen”.

    It does mention that other conditions are needed (UV light exposure, heat, and metallic ions).  I was just trying to eliminate any possible issues arising and avoided it incase something didn’t go right.  Do you think I went a bit overboard on the Chelators too?

    Again thank you so much for taking the time to respond.

  • pharma

    Member
    September 18, 2019 at 4:47 pm
    I might go with gluconolactone (“slow release”) and citric acid (immediate effect) but then again, wait what those with more practical experience have to say. For personal use where a slight increase in cost and labour doesn’t matter, it’s not a bad thing to go a bit overboard. Better save than sorry, right?
    Head space is the air in the container/tube/bottle. That’s where mould starts first (-> fruit jam).
    Benzoate and ascorbic acid combination is in fact something which is disadvised because of the possible degradation. Although, it seems to be done frequently… if it poses a real life problem, I do not know, can’t remember the article I read about a while back.
  • markbroussard

    Member
    September 18, 2019 at 5:00 pm

    Agreed … better to go overboard than not.

    Yes, the Ascorbic Acid + Sodium Benzoate argument is overblown … unless you are adding both at high temperature for extended periods of time, you simply will not reach the activation energy level to effect a reaction.  And, yes, it is done frequently.

  • DIY_Newbie

    Member
    September 20, 2019 at 3:20 am

    Thank you again for your replies.  I will try it out and see how it goes.  I will look into phenethyl alcohol and see if its available to buy in limited quantities. I appreciate all the feedback.

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