Flow Injection Analysis of Anionic Surfactants in River Water Using Teflon Filter Tube Preconcentration

A method was developed to determine anionic surfactants in river water using Teflon (PTFE) filter tube preconcentration. PTFE adsorbs hydrophobic and electrically neutral chemical species on its surface. This allows the surface of PTFE filter tube to adsorb and concentrate an ion pair formed between a cationic detecting agent and an anionic surfactant in aqueous solution. The detecting agent and the model anionic surfactant used were Co-5-Cl-PADAP, a highly sensitive detecting agent, and sodium dodecyl sulfate, respectively. After the ion pair was concentrated at a flow rate of 1.5mL/min for 5 min on a 7cm long filter tube (inner diameter: 1.5mm), the ion pair was eluted with ethanol at a flow rate of 2.0mL/min. The detection limit was 2ng mL-1 (3×standard deviation of blank). The sensitivity of this method was equal to or higher than that of the conventional solvent extraction method. This method and the Ethyl Violet method (EV method, JIS) gave somewhat different analytical results for a standard solution containing various anionic surfactants because the sensitivities of the methods are different for each surfactant, while they yielded the same analytical results for river water samples