Solid-contact ion-selective electrodes for aromatic cations based on pi-coordinating soft carriers

Ion-selective electrodes (ISEs) based on pi-coordinating carriers were prepared and investigated as potentiometric sensors for aromatic cations, using N-methylpyridinium as a model aromatic cation. Derivatives of tetraphenylborate were studied as charged carriers in plasticized poly(vinyl chloride) membranes. Furthermore, neutral compounds containing pi-coordinating anthryl groups were studied as neutral carriers. Bis(2-ethylhexyl)sebacate (DOS) and 2-nitrophenyl octyl ether (o-NPOE) were used as non-polar and polar plasticizer, respectively. ISEs were constructed by using poly(3,4-ethylenedioxythiophene) (PEDOT) as solid-contact material. Conventional ISEs with internal filling solution were used for comparison. The potentiometric responses of the ISEs were investigated using N-methylpyridinium as primary ion. The results show that the selectivity of the ISEs is influenced significantly by both the plasticizer and the charged carriers, while the neutral carriers studied have only a minor influence on the selectivity. The role of cation-pi interactions between aromatic cations and the membrane components is discussed.