Home Cosmetic Science Talk Formulating Preservation Q - Sodium Benzoate & Copper Distilled Hydrosols

  • Preservation Q - Sodium Benzoate & Copper Distilled Hydrosols

    Posted by Weatherend on June 19, 2024 at 7:17 am

    Hello all - thanks so much in advance for any advice.

    I’m looking to expand my Y/M coverage in an O/W emulsion formula that uses rose hydrosol distilled using a copper still. Sodium Benzoate is a strong contender (in partnership with PE9010 for bacteria coverage, sodium phytate and propanediol). pH is suited at 4.8.

    I read a post elsewhere here that noted that Sodium Benzoate in the presence of copper and iron ions “may undergo reactions that could affect the stability and safety of the product. Proper formulation and testing are crucial to ensure compatibility.” However, I can’t find additional information on this anywhere. Link to the original thread here: https://chemistscorner.com/cosmeticsciencetalk/discussion/what-ingredients-are-incompatible-with-sodium-benzoate/

    I know I have testing in my future, but want to ensure that I shouldn’t be ruling this material out from the get go given a potential incompatibility with the hydrosol. Appreciate your help!

    Weatherend replied 3 weeks, 6 days ago 2 Members · 6 Replies
  • 6 Replies
  • PhilGeis

    June 19, 2024 at 8:12 am

    Do NOT trust your preservation to hydrosols - in whole or in part. If preservation is the only reason for their intended use - use is unreasonable.

    These are not magic - they’re a mixture of unknown composition. To your question - you have no idea what’s in the stuff. From contaminants from production to pesticides from agriculture and most importantly the compounds putatively responsible for implied efficacy.

    • Weatherend

      June 19, 2024 at 5:55 pm

      @PhilGeis thank you so much for taking the time to reply. I’ve benefited hugely from the knowledge and expertise you’ve generously shared in this forum and am just finishing up your book.

      I wanted to clarify my question and ask a follow up based on your response.

      To clarify: Hydrosol is NOT part of my preservation system. My question is actually the opposite, is it possible (probable) that hydrosol - specifically copper by-products from the distillation process can cause destabilization of sodium benzoate. I read elsewhere that copper can have this effect, but could not find substantiating information.

      Stated more broadly, because hydrosol is a more specific use case and a bit of red herring to the actual question:

      Is it true that in the presence of certain metal ions, such as <strong style=”font-family: inherit; font-size: inherit; color: var(-bb-body-text-color);”>copper or iron, sodium benzoate may undergo reactions that could affect the stability and safety of the product and undermine its preservative function?

      Apologies if I misunderstood your original reply.

      • PhilGeis

        June 19, 2024 at 6:50 pm

        Thanks for clarification. Kinda doubt would be enough copper to screw up your benzoate. Look for the blue complex and precipitate.

        Can you get your supplier to put Cu on CoA?

        • Weatherend

          June 20, 2024 at 7:46 am

          Thanks again @PhilGeis - I can definitely look into getting that as part of analysis.

          Is there a known ppm for Copper that has been established as a baseline for interference with Sodium Benzoate? Once I have the updated CoA info, will need some sort of reference point for the break point.

          • PhilGeis

            June 20, 2024 at 8:03 am

            CoA should come from your supplier based on what is and what they can detect and control.

            As to threshold for benzoate complexation, what is hydrosol % in product?

            • Weatherend

              June 20, 2024 at 8:09 am

              @PhilGeis ok got it.

              Hydrosol is about 65% (it’s the water part of water phase) making it a significant contributor to what goes on overall in the formula. Overall, I’ve found rose hydrosol to have a lot of quirks from a stability perspective, so its really been an ongoing experiment and learning tool for me.

              Thanks again for your help expanding my knowledge in this area.

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