1.1This test method covers a potentiometric titration procedure for determining active matter in disinfectant quaternary ammonium salts. This test method is intended for the analysis of quaternary ammonium salts used as disinfectants, and only applies to the following commonly used quaternary ammonium salts: n-alkyldimethylbenzylammonium chloride (see Fig. 1), cetyltrimethylammonium chloride, and a blend of n-octyldecyl dimethylammonium chloride, di-n-octyl dimethylammonium chloride, and di-n-decyldimethyl ammonium chloride (see Fig. 2). Also, this test method can be applied to the analysis of disinfectant type products where the formula ingredients are known and the quaternary ammonium salt is one of the above. Interferences such as amines oxides and betaines present in disinfectant formulations were not tested.