This International Standard specifies a manual or mechanical method for the determination of anionic-active matter present in detergents. The method is applicable to solids or to aqueous solutions of the active material. The relative molecular mass of the anionic active matter has to be known. The method is not applicable if cationic surface active agents are present. The manual method is thus applicable to the determination of alkylbenzene sulfonates; alkane sulfonates, sulfates and hydroxysulfates; alkylphenol sulfates; fatty alcohol methoxyand ethoxysulfates ; dialkylsulfosuccinates and other active materials containing one hydrophilic group per molecule. The mechanical method is applicable to all the abovementioned products provided it gives results comparable with those obtained using the manual method. NOTE - Low relative molecular mass sulfonates present as hydrotropes (toluene, xylene) do not interfere when present in concentrations of up to 15 % (mlm) relative to the active matter. At higher levels, their influence should be evaluated in each particular case. Soap, urea and salts of (ethylenedinitrilo)tetraacetic acid do not interfere. In the presence of non-ionic surface agents, their influence should be evaluated in each particular case. Typical inorganic components of detergent formulations, such as sodium chloride, sulfates, borates, tripolyphosphates, perborates, silicates, etc., do not interfere, but bleaching agents other than perborate should be destroyed before the analysis, and the Sample should be completely soluble in water.