Spectrophotometric Determination of Cationic Surfactants Using Patent Blue V: Application to the Wastewater Industry in Algiers

Abstract

Patent Blue V has been applied in a solvent extraction spectrophotometric method for the determination of cationic surfactants (CS) in industrial wastewaters. The method is based on the introduction of Patent Blue V as an anionic dye, and the formation of an ion pair association with CS in chloroform under the studied extraction conditions. The maximum wavelength of absorption for the ion pair is located at 627 nm, and a molar absorption coefficient of higher than 3.6 × 10⁵ l mol⁻¹ cm⁻¹ was obtained. The calibration curve was linear between 0 and 5.48 × 10⁻⁶ M, and exhibited a significant coefficient of correlation. Based on the calculated values for the relative standard deviation (%) over the studied concentration range, the method was found to be highly sensitive, and the deduced limit of detection for the method was found to be very low (8.6 × 10⁻⁸ M of CTAB). It was also found that a washing step was necessary for the organic extract in order to remove interferences caused by foreign ions and species present in unknown samples. To validate this method, the procedure was used to determine the CS contents of samples collected from textile industry wastewaters in the Algiers region. The results obtained showed good agreement for the proposed method.