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

Abstract

Sol-gel and polymeric membrane electrodes, based on thiacalix[4]arene as a neutral carrier, were<br />successfully developed for the detection of VO2+ in aqueous solutions. The sol-gel and PVC<br />membrane electrodes exhibited linear response with Nernstian slopes of 29.3 and 28.4 mV per<br />decade, respectively, within the vanadyl ion concentration ranges from 1.0 × 10-6 to 1.0 × 10-1<br />mol dm-3 and from 1.0 × 10-5 to 1.0 × 10-1 mol dm-3 for sol-gel and PVC membrane sensors.<br />The PVC-based and sol-gel electrodes show detection limits of 3.1 × 10-6 and 4.9 × 10-7 mol dm-<br />3, respectively, and also response time of about 15 s to achieve a 95% steady potential for VO2+<br />concentration. By testing the stability lifetimes of the electrodes over a six-month period, no<br />significant change was observed in the performance of the sol-gel electrode, however, the PVCbased<br />vanadyl-selective electrode exhibited a gradual decrease in the slope after two months.<br />Investigating the influence of membrane composition, the pH of the test solution, and the<br />interfering ions on the electrodes performance revealed good selectivity of electrodes for a number<br />of alkali, alkaline earth, transition and heavy metal ions. The determined isothermal temperature<br />coefficients of these electrodes showed a better thermal stability of sol-gel electrode rather than<br />that of the PVC-based vanadyl-selective electrode, however, the electrodes performance is<br />deteriorated by temperatures higher than 50 °C.