Carbon Black Single Piece Electrodes for Nitrate Ion Sensing

This work presents an idea for a new reliable potentiometric sensor for nitrate ion determination. The paper provides the optimized procedure for the preparation and maintenance of single-piece nitrate-selective electrodes with carbon black nanoparticles. The optimal carbon black amount was selected based on the electrical properties of the designed sensors. The 5% addition of carbon nanomaterial to the polymeric membrane ensured the highest electrical capacitance (of 610 µF) and the lowest resistance (of 421 kΩ); therefore, this amount was further applied to design single-piece sensors. The influence of carbon black incorporation into the membrane on the analytical performance of the nitrate-selective electrodes was investigated, focusing on parameters such as sensitivity, selectivity, detection limit, and potential stability. Carbon black-modified nitrate-selective sensors exhibit a near-Nernstian response in a wide range of nitrate ion concentrations (with a detection limit of 7 × 10^-7). Remarkable potential stability, ensured by the hydrophobic properties of the modified membrane, was evaluated during the water-layer test and the calculated potential drift equaled 0.052 mV/h.