A novel electrochemical glucose sensor was developed, based on a multiwall carbon nanotubes (MWCNTs)-copper-1,3,5-benzenetricarboxylic acid (CuBTC)-epoxy composite electrode, named MWCNT-CuBTC. The electrode nanocomposite was prepared by a two-roll mill procedure and characterized morphostructurally by scanning electron microscopy (SEM). The CuBTC formed defined crystals with a wide size distribution, which were well dispersed and embedded in the MWCNTs. Its electrical conductivity was determined by four-point probe contact (DC) conductivity measurements. The electroactive surface area, determined using cyclic voltammetry (CV), was found to be 6.9 times higher than the geometrical one. The results of the electrochemical measurements using CV, linear sweep voltammetry (LSV), differential pulse voltammetry (DPV), chronoamperometry (CA) and multiple pulse amperometry (MPA) showed that the MWCNT-CuBTC composite electrode displayed high electrocatalytic activity toward the oxidation of glucose and, as a consequence, very high sensitivity. The best sensitivity of 14,949 µAmM⁻¹cm⁻¹ was reached using MPA at the potential value of 0.6 V/SCE, which was much higher in comparison with other copper-based electrodes reported in the literature. The good analytical performance, low cost and simple preparation method make this novel electrode material promising for the development of an effective glucose sensor.

Ammonium and nitrite are listed by Water Framework Directive as core parameters that should be monitored for the groundwater as drinking water source. This work describes the sensitive protocols for the simultaneous detection of ammonium and nitrite in water at a new silver-electrodecorated carbon nanotubes-epoxy composite electrode (Ag-CNT) using advanced voltammetric technique. A carbon nanotubes-epoxy composite electrode obtained by two-roll mill procedure was decorated electrochemically with silver nanoparticles. This new electrode displays excellent electrocatalytic activity towards the direct oxidation of ammonium and nitrite at well separated less potential values (+0.15 V/SCE for ammonium and +0.7 V/SCE for nitrite). Very good detection sensitivities (0.613 mA mM⁻¹ for ammonium and 0.980 mA mM⁻¹ for nitrite) and the lowest limits of detection (1 μM for ammonium and 0.7 μM for nitrite) were achieved by differential-pulsed voltammetry (DPV) under optimum operating conditions of 0.05 V step potential, 0.2 V modulation amplitude and the scan rate of 0.05 V s⁻¹. This detection protocol was successfully applied to the simultaneous determination of ammonium and nitrite in groundwater samples, and the results were found to be consistent with the values obtained by the standardized spectrophotometry methods.