The electrochemical detection of ammonia in drinking water based on multi-walled carbon nanotube/copper nanoparticle composite paste electrodes

An attractive electrochemical protocol for measuring ammonia based on carbon nanotube (CNT)/copper composite paste electrodes is described. The novelty of this work concerns the observed catalytic action of the CNT/Cu composite material, demonstrating the possibility to detect ammonia at a low potential (−0.120 V versus Ag/AgCl) and at higher current values. These optimised composite electrodes showed significantly better performance than those obtainable from simple CNT or Cu paste electrodes (used here for comparison) in terms of linear range of concentration (3–100 μM), lower detection limit (3.47 μM), higher sensitivity (16.45 μA μmol−1 L cm−2), reproducibility (R.S.D.% of 4.65, n = 20), and response time of 8 s. Finally, the chemical sensors were applied to the determination of ammonia in real samples of tap water, spiking different ammonia concentrations directly into the water samples. The recovery study demonstrated that the slopes of standard addition curves and the common calibration plots are approximately the same, indicating the absence of a significant matrix effect in this medium.