[Goonie]

How would one go about calculating the % solids in a surfactant solution without ashing the sample?

[Stepan]

if this one time study, you will need to dry the solution no matter what. If this is the same surfactant/water solution and you need to build a fast method to measure surfactant level in let say your product, you can build correlation Concentration- density, concentration-refractive index, or concentration- conductivity and save yourself some time.