A flow injection system for the determination of nonionic surfactants in the presence of ionic surfactants was investigated. The system consists of a microcolumn packed with an ion-exchange resin and a surfactant-selective electrode using a plasticized polyvinyl chloride membrane containing no ion-exchange site. Ionic surfactants were removed on the microcolumn. Nonionic surfactants passed through the column with ethanol/H20 = 50/50 (v/v, %) were detected. The electrode showed the cationic potential response with a slope of 40 mV/decade for Triton X-100 from 4×10-5 to 5×10-4 M. The detection limit of Triton X-100 was 1 × 10-5 M. The proposed method is free from the interference of coexisting inorganic electrolytes in sample solutions. By this method, nonionic surfactants in detergent samples could be determined.
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