Quantitative Analysis of Cationic Surfactants with Methyl Orange

The cationic surfactants were determined spectrophotometrically with methyl orange in the presence of nonionic or amphoteric surfactant. The cationic surfactants react with methyl orange to decrease the absorbance of methyl orange solution. The maximum decrease is observed at 462 nm which is the absorption band in alkali region, and the absorbance is constant in the pH range of 6.08.0. The calibration curve for the determination of the cationic surfactants was obtained from the decrease of absorbance at 462 nm in the presence of 3.0×10-5M methyl orange at pH 6.90. Cetyl pyridinium chloride and myristyl benzyl dimethyl ammonium chloride could be determined in the presence of excess amount of polyoxyethylene lauryl ether or N-lauryl betain hydrochloride.