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5-(3-Bromo-4-hydroxy-5-methoxyphenyl)-7,7-dimethyl-7H-indolo[1,2-a]quinolinium perchlorate (Ia) was used as an indicator for anionic surface active agents determination in the manual direct two-phase titration according to the International Standard [ISO 2271:1989] Surface active agents. The solvatochromic dye (Ia) can successfully replace the recommended mixed indicator consisting of a mixture of Acid Blue I and carcinogenic dimidium bromide. The detection of the titration endpoint with use of this dye turned out much easier than with the use of the mixed indicator. The procedure was also modified replacing carcinogenic and mutagenic chloroform with less toxic dichloromethane. The concentrations of the anionic surface – active substances in few commercially available products were determined using modified two-phase titration method.

tenside surfactants detergents

5-(3-Bromo-4-hydroxy-5-methoxyphenyl)-7,7-dimethyl-7H-indolo[1,2-a]quinolinium Perchlorate as a New Indicator for Anionic Surface Active Agents Determination