Study of Cationic Surfactant Ion Selective Poly(vinyl chloride) Membrane Electrode Containing Dibenzo-18-crown-6

Abstract

Abstract Study was made of the potentiometric selectivities of poly(vinyl chloride) membrane with and without dibenzo-18-crown-6. It was found that these membrane electrodes were highly selective for cationic surfactant ions and showed a Nernstian response to surfactant ion such as 1-dodecylpyridinium ion even in the concentration range as low as 10−6 mol/dm3. The selectivity coefficients of inorganic cations, taken with respect to 1-dodecylpyridinium ion, were of the order of 10−5 or less, while that of surfactant ion was found to depend not only on hydrophobic alkyl chain length but also on the type of hydrophilic head group. For cationic surfactants with the same hydrocarbon chain length, the membrane without crown ether exhibited the order of selectivity: 1-alkylpyridinium ion>alkyltrimethylammonium ion>alkylammonium ion. In the case of the membrane with crown ether, the selectivity sequence became alkylammonium ion>1-alkylpy ridinium ion>alkyl trimethylammonium ion. For a homologous series of cationic surfactants, the selectivity coefficient increased regularly with increasing alkyl chain length.