Home Cosmetic Science Talk Formulating ph changing in stability test

  • ph changing in stability test

    Posted by em88 on January 11, 2018 at 12:00 pm

    Greetings,

    I am working on a cream and I have noticed that the pH changes over time in the stability test, more noticeable in accelerated conditions.

    Ingredients: Methyl salicylate, menthol, sodium cetostearyl
    sulfate and Cetostearyl alcool, xanthan gum, glycerine, water

    I have noticed in the preparation process, if I melt the oil phase at 60-70 C the pH is around 6.5 and it drops to 6 after a month is the stability in accelerated conditions
    If I melt the oil phase at 50-60 C the pH is about 7.5 but it drops to 7 in normal conditions and 6.1 in accelerated conditions (1 month). 

    What might be the cause? 

    Thank you

    em88 replied 6 years, 3 months ago 3 Members · 5 Replies
  • 5 Replies
  • Chemist77

    Member
    January 11, 2018 at 4:28 pm

    Breakdown of menthyl salicylate to acid??

  • Bill_Toge

    Member
    January 12, 2018 at 12:51 am

    at a guess, the fact there are no salts that can act to stabilise the pH; something as simple as disodium EDTA can be very beneficial in this regard

    however, my bigger concern is that there appears to be no preservative

  • em88

    Member
    January 12, 2018 at 8:07 am

    @Chemist77, good point. I thought methyl salicylate was stable. 

    @Bill_Toge, I was thinking of adding something to stabilise the pH. Thank you for the suggestion. Regarding the preservatives, I have seen several similar products in the market and none of them had preservatives. I guess having a high % of methyl salicylate and menthol was enough to avoid preservatives. 

  • Chemist77

    Member
    January 12, 2018 at 11:04 am

    @em88 it is purely a guess, since pH is involved and the only logical point is presence of a component responsible for pH drop. 

  • em88

    Member
    January 15, 2018 at 8:13 am

    Has anyone else faced this?

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