Potential Reproducibility of Potassium-Selective ElectrodesHaving Perfluorinated Alkanoate Side Chain Functionalized Poly(34-ethylenedioxytiophene)as a Hydrophobic Solid Contact

摘要

The irreproducibility of the standard potential (E°) is probably the last major challenge for the commercialization of solid-contact ion-selective electrodes (SCISEs) as single-use or wearable sensors. To overcome this issue, we are introducing for the first time a perfluorinated alkanoate side chain functionalized poly(3,4-ethylenedioxythiophene) (PEDOTF) as a hydrophobic SC in potassium-selective electrodes (K-SCISEs) based on plasticized poly(vinyl chloride). The SC incorporates the tetrakis(pentafluorophenyl)borate (TFAB^–) anion, which is also present as a lipophilic additive in the ion-selective membrane (ISM), thus ensuring thermodynamic reversibility at the SC/ISM interface and improving the potential reproducibility of the electrodes. We show here that the PEDOTF-TFAB solid contact, which was prepolarized prior to the ISM deposition to either its half or fully conducting form (i.e. different oxidation states) in acetonitrile containing 0.01 M KTFAB, had a very stable open-circuit potential and an outstanding potential reproducibility of only ±0.5 mV (n = 6) for 1 h in the same solution after the prepolarization. Thisshows that the oxidation state of the highly hydrophobic PEDOTF-TFABfilm (water contact angle 133°) is stable over time and can beprecisely controlled with prepolarization. The SC was also not lightsensitive, which is normally a disadvantage of conducting polymerSCs. After the ISM deposition, the standard deviation of the E° of the K-SCISEs prepared on glassy carbon was ±3.0mV (n = 5), which is the same as that for conventionalliquid contact K-ISEs. This indicates that the ISM deposition is themain source for the potential irreproducibility of the K-SCISEs, whichhas been overlooked previously.