Flow-Through Cell for Ion-selective Electrodes
Asein, Enahoro Aigboje (2023)
Asein, Enahoro Aigboje
Julkaisu on tekijänoikeussäännösten alainen. Teosta voi lukea ja tulostaa henkilökohtaista käyttöä varten. Käyttö kaupallisiin tarkoituksiin on kielletty.
Julkaisun pysyvä osoite on
This research work describes a novel flow-through all-solid-state potentiometric device that consists of solid-contact ion-selective electrodes and a solid-state planar reference electrode. The device is capable of measuring ionic concentrations in small sample volumes. Planar potassium ion-selective electrodes (K-ISEs) and chloride ion-selective electrodes (Cl-ISEs) were made using carbon cloth (CC) as ion-to-electron signal transducer (CC-ISEs). Polyvinyl butyral/sodium chloride (PVB/NaCl)-based and polyvinyl acetate/potassium chloride (PVAc/KCl) composite-based reference electrodes were prepared using silver/silver chloride disk electrodes and characterized. The PVAc/KCl composite-based reference electrode showed superior performance and was selected for use in the flow-through device. Carbon cloth and polycarbonate (PC) were tested as substrates for the fabrication of the planar PVAc/KCl composite-based reference electrode. The reference electrode made using the CC substrate (CC-RE) performed well when used with either an external commercial reference electrode or a chloride ion-selective electrode. However, the construction and assembly of the CC-RE made it perform poorly when combined with a CC-ISE in one cell. The PC-based reference electrode (PC-RE) solved the issues associated with the CC-RE and performed well when combined with CC-ISEs in the complete flow-through potentiometric device. When measured against the PC-RE, the potassium and chloride CC-ISEs (K- and Cl-ISEs) consistently showed fast and stable near-Nernstian responses, good R2 values, and high within-day repeatability in the 10–3 M to 10–1 M KCl concentration range. The use of valinomycin as ionophore in the studied K-ISEs resulted in excellent selectivity for the electrodes in the presence of interfering ions such as Na+, Mg+, and Ca2+. Whereas the Cl-ISEs based on the ion exchanger tridodecylmethylammonium chloride (TDMAC) showed relatively poor selectivity in the presence of interfering ions such as bicarbonate (HCO3–) and lactate (C3H5O3–). These ions were selected for the selectivity measurements due to their significant presence in sweat samples that are meant to be measured using the flow-through device. The standard potentials of both potassium and chloride CC-ISEs demonstrated poor reproducibility in between-electrode and between-day measurements. Results from the electrochemical impedance spectroscopy measurements, carried out using the K-ISEs, showed that the resistance of the valinomycin-based potassium ion-selective membrane (ISM) is relatively high in these electrodes compared to the values reported in the literature. In addition, electrodes made in a similar way and are supposed to be identical exhibited different values of ISM resistance. This can be attributed to errors in the manual fabrication of the electrodes. Despite the high (charge transfer) resistance values of the ISMs, the CC-ISEs showed fast and relatively stable potentiometric responses.
- 116 Kemia