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Quantitative determination of dodecyl sulfate and dioctyl sulfosuccinate has been performed with methylene blue dye in titration mode. The new approach consists in the titration of surfactant solution by standardized dye solution, simultaneously measuring absorbance at 660 nm with an immersion probe. Due to the formation of sparingly soluble ion pairs, the registered photometric titration curves are dependent on surfactant concentration. The analytical signal is the titrant volume needed to reach a certain absorbance value. The main advantage of the proposed method is that no toxic organic solvent is used. An additional advantage is that the analysis procedure can be carried out using an automatic titrator. The determination range is dependent on the end-point absorbance value. Standard deviation values fall in the range from 2 to 7 %. The method may be useful for routine process control in the surfactant industry. [ABSTRACT FROM AUTHOR]