Photometric determination of cationic surfactants in aqueous solutions using methylene blue and silica gel

The method is based on the coadsorption of surfactants and Methylene Blue u nder batch conditions. It was found that the color intensity of the Methyle ne Blue solution determined photometrically is proportional to the amount o f the adsorbed surfactant. It is proposed to use silica gel as an adsorbent in the determination of cationic surfactants. The concentration of surfact ants is determined using a calibration plot. This method is suitable for th e determination of 0.002-1 g/L of quaternary ammonium compounds and amine s alts. The relative error of the determination is 6-12%. The detection Limit for technical surfactants under study is 0.4-8 mg/L.