Comparison of the vanadyl-selective electrodes prepared by sol–gel and PVC membrane techniques

Sol-gel and polymeric membrane electrodes, based on thiacalix[4]arene as a neutral carrier, weresuccessfully developed for the detection of VO2+ in aqueous solutions. The sol-gel and PVCmembrane electrodes exhibited linear response with Nernstian slopes of 29.3 and 28.4 mV perdecade, respectively, within the vanadyl ion concentration ranges from 1.0 × 10-6 to 1.0 × 10-1mol dm-3 and from 1.0 × 10-5 to 1.0 × 10-1 mol dm-3 for sol-gel and PVC membrane sensors.The PVC-based and sol-gel electrodes show detection limits of 3.1 × 10-6 and 4.9 × 10-7 mol dm-3, respectively, and also response time of about 15 s to achieve a 95% steady potential for VO2+concentration. By testing the stability lifetimes of the electrodes over a six-month period, nosignificant change was observed in the performance of the sol-gel electrode, however, the PVCbasedvanadyl-selective electrode exhibited a gradual decrease in the slope after two months.Investigating the influence of membrane composition, the pH of the test solution, and theinterfering ions on the electrodes performance revealed good selectivity of electrodes for a numberof alkali, alkaline earth, transition and heavy metal ions. The determined isothermal temperaturecoefficients of these electrodes showed a better thermal stability of sol-gel electrode rather thanthat of the PVC-based vanadyl-selective electrode, however, the electrodes performance isdeteriorated by temperatures higher than 50 °C.