This document specifies a method for the determination of the content of anionic surface active agents in raw materials, defined as being the amount of anionic surface active agents expressed in millimoles per 100 g of product. NOTE 1 The applicability in products different than those tested should be checked in each particular case. NOTE 2 In comparison to usual laboratory two-phase titration with visual endpoint determination (see ISO 2271) potentiometric titration offers the advantage of automation, operator-dependent differences in recognising the equivalence point can be neglected, and a non-critical solvent replaces the toxicologically critical chloroform.