Need solvent for hydrophobic powder to take pH reading

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?

Comments

  • Just curious what solvents you tried so far.
  • 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'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. 
  • 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.
  • PharmaPharma Member, Pharmacist
    10% methanol should be fine. However, not every alcoholic solution can easily be measured ;) .
  • PhilGeisPhilGeis Member, Professional formulator
    What is the relevance of this method for measuring pH?
  • PharmaPharma Member, Pharmacist
    @PhilGeis Fun? Claim? Too much free time? Finally a use for the pH meter? :smiley:
  • PhilGeisPhilGeis Member, Professional formulator
    Pharma!!!  Got it!
  • 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.
  • PharmaPharma Member, Pharmacist
    @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_TogeBill_Toge Member, Professional Chemist
    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
    UK based formulation chemist. Strongest subjects: hair styling, hair bleaches, hair dyes (oxidative and non-oxidative) I know some stuff about: EU regulations, emulsions (O/W and W/O), toothpaste, mouthwash, shampoos, other toiletries
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