Need solvent for hydrophobic powder to take pH reading

mbach

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?

biofm

Just curious what solvents you tried so far.

mbach

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

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

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

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

PhilGeis

What is the relevance of this method for measuring pH?

Pharma

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

PhilGeis

Pharma!!!  Got it!

mbach

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

@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

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