Abstract
Significant agricultural and industrial activities necessitate the regular monitoring of nitrate (NO3-) ions levels in feed and groundwater. The current comparative study discloses an innovative user-friendly electrochemical approach for the determination of NO3- over polyaniline (PAni)-based modified electrodes. The electrochemical sensors concocted with PAni, multi-walled carbon nanotubes (CNT), and gum arabic (GA). The unique electrode material GA@PAni-CNT was synthesized by facile one-pot catalytic polymerization of aniline (Ani) with FeCl3/H2O2 in the presence of CNT and GA as integral components. As revealed by cyclic voltammetry (CV), the anchoring/retention of NO3- followed by reduction is proposed to occur when a GA@PAniCNT electrode is immersed in phosphate buffer electrolyte containing NO3- that eventually results in a significantly higher redox activity of the GA@PAni-CNT electrode upon potential scan. The mechanism of NO3- anchoring may be associated with the non-redox transition of leucomeraldine salt (LS) into emeraldine salt (ES) and the generation of nitrite (NO2-) ions. As a result, the oxidation current produced by CV for redox transition of ES pernigraniline (PN) was similar to 9 times of that obtained with GA@PAni-CNT electrode and phosphate buffer electrolyte, thus achieving indirect NO3- voltammetric determination of the GA@PAni-CNT electrode. The prepared GA@PAni-CNT electrode displayed a higher charge transfer ability as compared to that of PAni-CNT and PAni electrodes. The optimum square wave voltammetric (SWV) response resulted in two linear concentration ranges of 1-10 (R-2 = 0.9995) and 15-50 mu M (R-2 = 0.9988) with a detection limit of 0.42 mu M, which is significantly lower. The GA@PAni-CNT electrode demonstrated the best detection, sensitivity, and performance among the investigated electrodes for indirect voltammetric determination of NO3- that portrayed the possibility of utilizing GA-stabilized PAni and CNT nanocomposite materials in additional electrochemical sensing applications.