Development of a highly selective and sensitive sulfate—polymeric membrane sensor based on Nickel(II)–dioxime complex as neutral carrier

A novel sulfate–poly(vinyl chloride) (PVC) membrane based on nickel complex of 3,8-dimethyl-5,6-benzo-4,7-diazadece-3,7-diene-2,9-dione (dioxime) was prepared and used as a sensor for sulfate ions in solution. The proposed sensor revealed an excellent linear response towards SO42- ion in the concentration range of 5.0 × 10–7 to 1.0 × 10–2 M with an anionic slope of −30 ± 0.2 mV per decade. The potentiometric behavior of the sensor was independent of the pH of the solution in the range of 4.5–7.5. The fabricated sensor showed an outstanding reproducibility, fast response time, and with a low detection limit as 3 × 10–7 M. The interference of hydrophobic inorganic anions was very low in comparison with the conventional ion-exchanger-based electrodes, as shown by the selectivity coefficients determined by the separate solution method. The sensor also was used successfully as an indicator electrode in the potentiometric titration of sulfate with barium ions and in quantification and quality assessment of sulfate in some pharmaceutical formulations.