The Analysis of Anionic Surfactants in Effluents Using a DDA-TPB Potentiometric Sensor

A new, simple, sensitive, accurate and inexpensive potentiometric sensor for the determination of anionic surfactants (AS) based on the dimethyldioctadecylammonium-tetraphenylborate (DDA-TPB) ion pair as a sensing material was used for end-point detection during the potentiometric titrations of low levels of AS in industrial effluents. Solutions of cetylpyridinium chloride (CPC) at concentrations as low as 5.10(-5) M were successfully used as a titrant. The accuracy and precision of the measurements were determined using the standard addition method, and satisfactory results were obtained, with recoveries between 98.3 to 102.0 % in pure AS solutions and 99.0 to 114.5 % in effluents. The AS concentration in effluents ranged between 2.64 and 176.7 mg/L. The results were compared with a standard spectrophotometric Methylene Blue Active Substances (MBAS) method, and they indicated a satisfactory correlation. The influence of the different pH values (2-10) and ionic strengths (0.003-0.301) on the shape of the potentiometric titration curves and the response characteristics of the sensor were examined.