Home Cosmetic Science Talk Formulating How should I determine a functional pH for a preservative that has a recommended pH range.

  • How should I determine a functional pH for a preservative that has a recommended pH range.

    Posted by ccisco on October 19, 2022 at 8:47 pm

    Hi everyone! I am having a discussion with my peers and it seems that we are in a bubble. We were discussing whether or not the pH range of a preservative depends on the initial water phase pH (in a O/W emulsion), the final water phase pH or both. We have been adjusting the water phase in order to fit the proper and recommended pH range to the preservative for most of our batches, however it came into discussion that it possibly is not necessary and that the pH mainly depends on the final pH of a O/W emulsion or both. I would like to hear you guys out on any information regarding to this.

    PhilGeis replied 1 year, 8 months ago 4 Members · 6 Replies
  • 6 Replies
  • Graillotion

    Member
    October 19, 2022 at 11:42 pm

    Are you finding that the final pH is dramatically different than your water phase pH?

    When are you adjusting pH?

    I find very little variation between adjusted water phase pH…and final pH….Hence I adjust pH in my water phase only.  (And double check final pH.)

  • Paprik

    Member
    October 20, 2022 at 12:13 am

    Final product pH is important. It must be within the range that supports actives, preservative, etc … 

    Usually you do not need to adjust pH of your water phase. 

    Even if you do and you add some kind of actives at the end (or preservatives for that matter, such as Geogard ECT) it will shift your pH. 

    So finish your product [completely] and adjust final pH.

    The preservative usually does not get destroyed by “wrong” pH. It only won’t be effective.

  • PhilGeis

    Member
    October 20, 2022 at 1:20 pm

    pH must be addressed throughout making as well as in final product and mistakes in order of addition can screw up preservation.  Tho’ stable in the finished product, some can hydrolyze/precipitate within the making process due to brief or spatial excursions in pH, solubility, chelators, etc.
    Alkaline pH and simple aqueous solution will degrade Kathon, parabens can react with carbohydrates, clays and cyclodextrin can absorb preservatives, sorbate auto-oxidizes at higher pH, etc. 

  • Graillotion

    Member
    October 20, 2022 at 6:57 pm

    PhilGeis said:

    pH must be addressed throughout making as well as in final product and mistakes in order of addition can screw up preservation.  Tho’ stable in the finished product, some can hydrolyze/precipitate within the making process due to brief or spatial excursions in pH, solubility, chelators, etc.
    Alkaline pH and simple aqueous solution will degrade Kathon, parabens can react with carbohydrates, clays and cyclodextrin can absorb preservatives, sorbate auto-oxidizes at higher pH, etc. 

    You read my mind!!!

    Sadly, the mommy blogger sites train nonprofessionals to only adjust at the end…one more nail in the coffin of preservation. :( 

    I was going to ask this question…even thought I do NOT formulate in this manner…. but I had assumed (guessed) that even though maybe only for a few minutes span…. the exposure to a less than ideal pH might have lasting effect.

    In other words…. even if you get the pH down in the end….the damage was done.

    I like to get the pH into the range of the finished product, as early as possible.

  • Graillotion

    Member
    October 20, 2022 at 6:59 pm

    @PhilGeis I have been overly intrigues with cyclodextrin, and can’t imagine it won’t end up on my bench in the next year.  Is there a process or technique….where it can be incorporated without causing possible issue with preservation?

    What about ‘pre-loading’ it with something like D5…to keep it ‘occupied’ while in formula, and until application?

  • PhilGeis

    Member
    October 20, 2022 at 9:19 pm

    @Graillotion
    I’ve seen it linked to water solubility of the preservative.  Parabens can be screwed up but CMIT is not affected.  BAK is also reduced in efficacy and recall it likes sorbate too. 

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