The determination is carried out as follows: Titration of an aliquiot portion of a sample solution with benzethonium chloride solution according to the direct two-phase titration procedure describes in ISO 2271. Hydrolysis by refluxing under alkaline conditions of a second aliquot portion of the sample solution. Titration of unhydrolyzed anionic-active matter with benzethonium chloride solution as before. Calculation of the contents of hydrolyzable and non-hydrolyzable anionic-active matter from the results obtained.