Home Cosmetic Science Talk Formulating Cosmetic Industry Resources Need solvent for hydrophobic powder to take pH reading

  • Need solvent for hydrophobic powder to take pH reading

    Posted by mbach on November 9, 2021 at 3:52 pm

    Hey there!

    I’m new to this forum. I’m having trouble figuring out what the standard procedure would be for stability on a hydrophobic, powdered dry shampoo. I need to be able to solubilize a competitor sample in order to test the pH. I’ve considered a small amount of surfactant that wouldn’t interfere with the potassium chloride in the pH probe. 

    Any thoughts?

    Bill_Toge replied 2 years, 7 months ago 6 Members · 11 Replies
  • 11 Replies
  • biofm

    Member
    November 9, 2021 at 4:19 pm

    Just curious what solvents you tried so far.

  • mbach

    Member
    November 9, 2021 at 4:56 pm

    A 1:10 methanol-water solution. It works, but I’m afraid the methanol will interact with potassium chloride and not give me an accurate reading

  • mbach

    Member
    November 9, 2021 at 5:09 pm

    I’ve also tried agitating with both a stir bar and shaking in a vial with a 100x water dilution, but only part of the powdered mixture is hydrophilic. Based on an EPA method - 1 part water, 1 part sample; agitate for ~5 minutes; remove solids; take pH of dissolved/dispersed solids. 

  • michalby

    Member
    November 10, 2021 at 12:00 am

    mbach said:

    A 1:10 methanol-water solution. It works, but I’m afraid the methanol will interact with potassium chloride and not give me an accurate reading

    I can confirm that it is ok to measure pH in methanol solutions, don’t worry about that.

  • Pharma

    Member
    November 10, 2021 at 5:41 am

    10% methanol should be fine. However, not every alcoholic solution can easily be measured ;) .

  • PhilGeis

    Member
    November 10, 2021 at 7:43 am

    What is the relevance of this method for measuring pH?

  • Pharma

    Member
    November 10, 2021 at 12:47 pm

    @PhilGeis Fun? Claim? Too much free time? Finally a use for the pH meter? :smiley:

  • PhilGeis

    Member
    November 10, 2021 at 1:51 pm

    Pharma!!!  Got it!

  • mbach

    Member
    November 10, 2021 at 2:36 pm

    I’m developing a powdered dry shampoo. This method is to measure stability in conditions of competitors. One of the competitors uses a hydrophobic ingredient (silica silylate) that makes it challenging to just use water as a diluent.

  • Pharma

    Member
    November 10, 2021 at 9:05 pm
    @mbach What exactly are you making? A dry shampoo for ‘dry washing’ or a dry base to be diluted with water and used as wet shampoo?
  • Bill_Toge

    Member
    November 11, 2021 at 6:09 pm
    if it’s hydrophobic, a pH measurement will be in no way useful
    pH is only meaningful with powders that dissolve in or are miscible with water

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