Effect of various additives on the performance of a newly developed PVC based potentiometric sensor for anionic surfactants

Abstract

A new poly(vinyl chloride) PVC membrane electrode to determine monomer concentrations of dodecylbenzenesulphonate ions (DBS −) based on a neutral ion-pair carrier complex of dodecyltrimethylammonium–dodecylbenzenesulphonate (DTA +–DBS −), is reported here. The electrode exhibits a slope of 51.25 mV per decade for DBS − ions. The DBS − ion selective electrode (ISE) can determine monomer units down to concentrations as low as 3.32 × 10 −4 M. The effect of three kinds of additives, i.e. alcohols, glycols and triblock polymers on the performance of the surfactant selective electrode is studied systematically. 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 interference method (FIM) at 1.0 × 10 −2 M concentration of foreign anions. The sensor responds well to the surfactant ions in the presence of additives at lower concentration. The Gibbs free energy of micelle formation (Δ G m) of sodium dodecylbenzenesulphonate (SDBS) in the presence of various additives is calculated and found to vary differently with respect to the increase in the amount of additives. The sensor worked in the acidic pH range with a short response time of 30 s. The lifetime of the sensor is more than three months. The sensor was further used to determine the amount of DBS − in local detergents. This method of determining anionic surfactants was found to be quite accurate when compared with classical methods.