Improved Nitrate Sensing Using Solid Contact Ion Selective Electrodes Based on TTF and Its Radical Salt

Abstract

The possibility of improving the selectivity of solid-state nitrate-selective electrodes by the application of the tetrathiafulvalene (TTF) or its nitrate salt (TTF(NO3)) as an intermediate layer between an electrical conductor and a polymeric membrane is demonstrated. The analytical performance of electrodes was investigated during potentiometric measurements. Fabricated sensors displayed a Nernstian slope (−58.85 mV/decade in the range from 10−5.0 to 10−1 M and −59.36 mV/decade in the range from 10−6.0 to 10−1 M for TTF− and TTF(NO3)−modified electrodes respectively), repeatable and reproducible standard potential and detection limit of 2.5 μM (0.16 mgL−1) and 0.63 μM (0.039 mgL−1) for TTF− and TTF(NO3)−based electrodes, respectively. The selectivity was considerably improved compared to a coated disc electrode or electrodes with intermediate layer based on carbon nanomaterials. Electrical parameters of the proposed sensors were tested by carried out current-reversal chronopotentiometry. In the case of electrodes with the use of TTF or TTF(NO3) the potential drift decreases to 167 μVs−1 or 16.6 μVs−1 and the capacitance is 5.99 μF or 60.3 μF. The proposed sensors were successfully applied in analyzing nitrate concentration in water samples.