| Popis: |
Solid-contact ion-selective electrodes (ISEs) have the inherent advantage of being miniaturized in addition to maintaining high selectivity and sensitivity of the ionophore-based ISE. The major disadvantage of ISEs is the necessity of performing a calibration curve (varying the intercept in the linear calibration curve equation) each time before running experiments, which limits their application as one-time disposable sensors or for use in remote water sample analysis. To overcome these challenges, we designed a unique back contact made of 3,4-ethylenedioxythiophene (EDOT) and 4-(2,3-dihydrothieno[3,4-b][1,4]dioxin-2-ylmethoxy)-1-butanesulfonic acid, sodium salt (EDOT-S). The calibration-free ISEs showed near Nernstian responses of 57.2 ± 0.2 mV/log [K(+)] and 28.5 ± 0.3 mV/log [Ca(2+)], while maintaining their respective selectivity against major interfering ions. The detection limits for Ca(2+) and K(+) ISEs were 0.45 ± 0.01 and 1.68 ± 0.18 μM, respectively. The charging cycles of the PEDOT: PEDOT-S back contact allowed us to fix the background potential at a desired fixed intercept value across different ionophores (K(+), Ca(2+)). This protocol was used to determine the K(+) and Ca(2+) contents in creek water samples. The activity and concentration of [Ca(2+)] and [K(+)] in a local creek was found to be 257 ± 7.3 and 28.1 ± 1.1 μM, respectively. |
