New poly(vinyl chloride) PVC membrane electrodes selective to the hexadecyltrimethylammonium ion (CTA + ) and sodium dodecyl ion (SD -) have been constructed using a modified single walled carbon nanotube (SWCNT). This sensor was used as a sensing material and incorporated into the plasticized PVCmembrane. The membrane electrodes exhibited a Nernstian response (59.5 mV/decade) for SDS and a near-Nernstian response (57.2 mV/decade) for CTAB over a wide concentration range below their critical micelle concentrations (CMC). The electrodes showed a fast response time (t90% = 30 s) and could be used for 3 months without any divergence in potentials. The SD -ion selective electrode (ISE) can determine monomer units down to concentrations as low as 1.9 Γ 10 -6 M and 5.2 Γ 10 -6 M for CTA + . The effect of foreign anions along with primary ions on the performance of ion-selective electrode is investigated in terms of potentiometric selectivity coefficients, which were determined using the fixed primary method (FPM) at 5.0 Γ 10 -5 M concentration of surfactant ions. The two proposed potentiometric sensors revealed acceptable selectivities for surfactant ions over a wide variety of other common inorganic and organic anions. The lifetime of the sensor is more than three months. This method for determining of anionic surfactants was found to be quite accurate when compared with classical methods.