[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.

[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. 

[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