Home Cosmetic Science Talk Formulating pH requirements for organic sunscreen filters

  • pH requirements for organic sunscreen filters

    Posted by evchem2 on April 20, 2023 at 8:10 am

    Are any of the following organic filters known to display instability if formulated in an emulsion at a pH ~5?





    I’ve heard these filters work best closer to neutral pH, but I haven’t seen anything on these ingredients specifically. They are all oil soluble as well so I’m having trouble understanding why a slightly acidic pH might be problematic. I have not formulated suncare products before, so I may be missing something obvious

    On a related note, if there are any textbooks/ resources for sunscreen formulation that anyone can recommend it’d be much appreciated.

    evchem2 replied 7 months, 1 week ago 3 Members · 4 Replies
  • 4 Replies
  • gordof

    April 28, 2023 at 12:46 am

    hi there

    one of the best books for sunscreen is even if it is a little older ISBN 9780824757946

    SunscreensRegulations and Commercial Development

    for your problem, i would go and discuss it with the suppliers of that kind of raw materials they have the moste data. As far as I know, there is no problem with a ph of 5 for avobenzone Homosalate and Octocrylene of Octisalate I am not sure.

    If you start Formulating suncare products you can use the various sunscreen formulators online like

    DSM SUNSCREEN OPTIMIZER™ (sunscreen-optimizer.com)

    Sunscreen Simulator (basf.com)

    These sides have a lot of information and are great tools to generate the basic Sunscreen composition even if it is not 100 % correct it still is a very good and easy starting point.

    • evchem2

      April 28, 2023 at 8:17 am

      Thank you for the recommendation, I appreciate it! I did look up supplier information (and a little bit of literature) and couldn’t find anything on these filters having any issues at my desired pH, that’s why I was confused by the response I got when I shared the planned formulation- this is just a model system to do some testing on, but I wanted it to be at least reasonable

  • marimaster_3991

    April 28, 2023 at 6:07 am

    hello, there!

    pH around 5,0-5,5 should not cause any instability issue, at least I’ve never had any trouble working with organic filters in this pH range. However, it’s different if you’re working with water-soluble filters, they usually need to be neutralized to avoid recrystallization, so the pH of the final product must be 7,0-7,5

    Just make sure you have the right ratio of avobenzone : octocrylene to stabilize avobenzone.

    • evchem2

      April 28, 2023 at 8:24 am

      Thank you, yes I was aware for filters like PBSA of the pH requirement, but didn’t find any glaring warning signs about these filters at this pH range. This is just a prototype and not for commercialization, but I’m basing it off a commercial US product so I’ve got my filter use levels from that.

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