The electrochemical methods-based protocol for simultaneous detection of tetracycline (TC) from antibiotics class and fluoxetine (FXT) from anti-depressive pharmaceuticals class, which belongs to emerging pollutants from water, was developed in this study using carbon nanofiber-epoxy composite electrode (CNF). The electrochemical behaviour of each pharmaceutical on CNF was considered the basis for simultaneous detection of both pharmaceuticals from water. TC electrooxidation on CNF occurred in two steps and, consequently, two detection potentials are considered. FXT electrooxidation occurred in one step that is overlaid to the first step of TC detection, this step being considered as cumulative for both pharmaceuticals. Each electrochemical method of cyclic voltammetry (CV) and differential-pulsed voltammetry (DPV) allowed detecting cumulative presence of TC and FXT at the detection potential ranged between 0.65 and 0.815 V vs. SCE and the selective detection of TC at the detection potential ranged between 0.956 and 1.14 V vs. SCE. The electroanalytical parameters related to the lowest limit of detection and sensitivity recommended this electrode to exhibit the potential for practical applications in the electrochemical detection of certain pharmaceuticals as emerging pollutants from water.

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.

Three types of composite electrode materials, i.e. carbon nanotubes-epoxy (CNT), zeolite-carbon nanotubes-epoxy (ZCNT) and TiO₂-modified zeolite-carbon nanotubes-epoxy (TiZCNT), were synthesized, morphologically and electrically characterized, and tested in the photoelectrodegradation of pentachlorophenol (PCP) from water. The electrode composite materials were synthesized by the two-roll mill method, and a higher porosity of zeolite-modified electrode, caused by the zeolite incorporation, was noticed by means of scanning electron microscopy. Electroactive surface area, determined by classical methods using cyclic voltammetry (CV), and electric conductivity, determined by the four-point method, were negatively affected by the presence of zeolite. The photoelectrochemical behaviour of the electrodes, under ultraviolet (UV) irradiation, towards the pentachlorophenol oxidation was studied, and the photoelectrocatalytic activity of each electrode was determined. The PCP oxidation occurred in two steps at +0.65 V and +0.94 V vs. saturated calomel electrode SCE under UV irradiation. The oxidation peak recorded at +0.65 V vs. SCE appeared only under UV irradiation and it is considered that the photoelectrooxidation peak corresponded to PCP photoelectrooxidation. Also, the enhancement of PCP electrooxidation at +0.94 V vs. SCE was noticed under UV irradiation, which confirmed the photelectrocatalytic activity. The performance of the PCP degradation process, expressed as degradation efficiency and electrochemical efficiency, recommended the operation of photoelectrocatalysis at a bias voltage application of +0.8 V/SCE, while the mineralization degree recommended a bias voltage value of +1.5 V/SCE.

Pharmaceuticals contaminants in waters exhibit a significant threat on the human health and the ecosystem quality. This research demonstrates the utility of a silver-doped zeolite-modified carbon nanofiber-epoxy (AgZ-CNF) prepared by two-roll mill method in development of the fast methodology for the detection of fluoxetine (FXT) in the aqueous solution. The results showed the role of zeolite that improved the sensitivity and the limit of detection of FXT resulted to the possibility to propose a specific preconcentration-based detection protocol. The silver contributed to decreasing the anodic over potential for FXT oxidation and hence, for FXT detection. The best sensitivity of 2.007 μA μM-1 and lowest limit of detection of 19 nM are were obtained for preconcentration-cyclic voltammetry based scheme, which is very promising for the detection of FXT at trace levels. Also, the chronoamperometry operated at 0.350 V/SCE specific to silver involving and +1.1V/SCE characteristics to the carbon nanofiber, allowed FXT detection in the aqueous solution. The long life time and the stable response for FXT detection was found for AgZ-CNF composite electrode, which suggests its practical utility in FXT determination in the real water sources.