Preparation of surfactant anion-selective electrodes with different selectivity coefficients and a trial to determine each component in binary surfactant mixtures

Functional membrane electrodes with different charge densities were prepared from partly cationic poly(vinyl chloride) (PVC) and a plasticizer. The modified PVC polymers were synthesized by the co-polymerization of vinyl chloride (VC) and 3-acrylaniido-NN-dimethylpropylamine (ADPA) in different ratios followed by alkylation of the amine segments with methyl iodide. These membrane electrodes showed a nearly Nernstian response to sodium dodecyl sulfate (SDS) below the critical micelle concentration (CMC). In mixtures of SDS and other surfactants, the electrode response was examined and the selectivity coefficient K-for the added surfactant was determined. The charge density of the functional membrane altered K, the greater the charge density of the membrane, the greater the value of K. Two membrane electrodes with different K were used to determine the concentration of each component in a binary surfactant mixture. They determined the concentration of the primary surfactant with reasonable accuracy, but the error in determining the concentration of the secondary surfactant was great. The error analysis indicated that a large difference in K for two electrodes is necessary to determine the concentrations of both components in binary surfactant mixtures with reasonable accuracy. (C) 2003 Elsevier Science B.V. All rights reserved.