Sodium dodocyl benzene sulphonate method of analysis

We are using Sodium Do-docyl benzene sulphonate as cleansing agent in our plant. We want to analyse the residue of the cleansing agent. So, could anybody provide me the method of analysis for sodium do-docyl benzene sulphonate.

We are also thinking of testing the residue in terms of the refractive index, surface tension and conductivity. Are those non specific test only enough to test the residue of cleansing agent? or we must go to TOC or specific method of analysis.

Suggestions are heartily welcomed.

Prawan Dahal