Highly sensitive and simultaneous electrochemical determinations of non-steroidal anti-inflammatory drugs in water using nanostructured carbon-based paste electrodes

Simple and fast simultaneous quantifications in water of anti-inflammatory drugs, which belong to the emerging pollutants, represents a great challenge for water quality control. The development of electrochemical methods to meet the simultaneous and concomitant detection requirements depends mainly on the electrode material. The fullerene‑carbon nanofiber (FULL/CNF) and graphene‑carbon nanotubes (GR/CNT) paste electrodes as sensing elements were employed for the first time for the determination of diclofenac (DCF), naproxen (NPX) and ibuprofen (IBP) simultaneously and concomitantly. The comparative morphostructural and electrochemical characterizations of both electrodes were achieved by scanning electron microscopy (SEM) and cyclic voltammetry (CV). Differential-pulsed voltammetry (DPV), chronoamperometry (CA) and multiple-pulsed amperometry (MPA) were used for detection tests. FULL/CNF electrode was suitable to develop a simultaneous DPV-based detection methodology that allowed reaching the lowest limit of detections of 0.230 nM for DCF, 0.310 nM for NPX and 0.180 nM for IBP. GR/CNT electrode did not provide stability for DPV-based detection, but the lowest limits of detection of 0.149 nM for DCF, 0.809 nM for NPX and 0.640 nM for IBP were achieved by MPA-based methodology. Both electrodes, linked to specific detection technique, showed good reproducibility, stability and ability to measure DCF, NPX and IBP simultaneously in aqueous solution. The satisfactory results achieved by analysis of real surface water sample (Bega River, Timisoara city, Romania) indicated that the proposed voltammetric and amperometric methodologies using both electrodes have great potential for practical applications in analysis of different water samples.

Enhanced Electrochemical Response of Diclofenac at a Fullerene⁻Carbon Nanofiber Paste Electrode

The requirements of the Water Framework Directive to monitor diclofenac (DCF) concentration in surface water impose the need to find advanced fast and simple analysis methods. Direct voltammetric/amperometric methods could represent efficient and practical solutions. Fullerene–carbon nanofibers in paraffin oil as a paste electrode (F–CNF) was easily obtained by simple mixing and tested for DCF detection using voltammetric and amperometric techniques. The lowest limit of detection of 0.9 nM was achieved by applying square-wave voltammetry operated under step potential (SP) of 2 mV, modulation amplitude (MA) of 10 mV, and frequency of 25 Hz, and the best sensitivity was achieved by four-level multiple pulsed amperometry (MPA) that allowed in situ reactivation of the F–CNF electrode. The selection of the method must take into account the environmental quality standard (EQS), imposed through the “watchlist” of the Water Framework Directive as 0.1 µg·L⁻¹ DCF. A good improvement of the electroanalytical parameters for DCF detection on the F–CNF electrode was achieved by applying the preconcentration step for 30 min before the detection step, which assured about 30 times better sensitivity, recommending its application for the monitoring of trace levels of DCF. The electrochemical behavior of F–CNF as a pseudomicroelectrode array makes it suitable for practical application in the in situ and real-time monitoring of DCF concentrations in water.

Electrochemical Selective and Simultaneous Detection of Diclofenac and Ibuprofen in Aqueous Solution Using HKUST-1 Metal-Organic Framework-Carbon Nanofiber Composite Electrode

In this study, the detection protocols for the individual, selective, and simultaneous determination of ibuprofen (IBP) and diclofenac (DCF) in aqueous solutions have been developed using HKUST-1 metal-organic framework-carbon nanofiber composite (HKUST-CNF) electrode. The morphological and electrical characterization of modified composite electrode prepared by film casting was studied by scanning electronic microscopy and four-point-probe methods. The electrochemical characterization of the electrode by cyclic voltammetry (CV) was considered the reference basis for the optimization of the operating conditions for chronoamperometry (CA) and multiple-pulsed amperometry (MPA). This electrode exhibited the possibility to selectively detect IBP and DCF by simple switching the detection potential using CA. However, the MPA operated under optimum working conditions of four potential levels selected based on CV shape in relation to the potential value, pulse time, and potential level number, and order allowed the selective/simultaneous detection of IBP and DCF characterized by the enhanced detection performance. For this application, the HKUST-CNF electrode exhibited a good stability and reproducibility of the results was achieved.

Electrochemical detection and degradation of ibuprofen from water on multi-walled carbon nanotubes-epoxy composite electrode

This work describes the electrochemical behaviour of ibuprofen on two types of multi-walled carbon nanotubes based composite electrodes, i.e., multi-walled carbon nanotubes-epoxy (MWCNT) and silver-modified zeolite-multi-walled carbon nanotubes-epoxy (AgZMWCNT) composites electrodes. The composite electrodes were obtained using two-roll mill procedure. SEM images of surfaces of the composites revealed a homogeneous distribution of the composite components within the epoxy matrix. AgZMWCNT composite electrode exhibited the better electrical conductivity and larger electroactive surface area. The electrochemical determination of ibuprofen (IBP) was achieved using AgZMWCNT by cyclic voltammetry, differential-pulsed voltammetry, square-wave voltammetry and chronoamperometry. The IBP degradation occurred on both composite electrodes under controlled electrolysis at 1.2 and 1.75 V vs. Ag/AgCl, and IBP concentration was determined comparatively by differential-pulsed voltammetry, under optimized conditions using AgZMWCNT electrode and UV-Vis spectrophotometry methods to determine the IBP degradation performance for each electrode. AgZMWCNT electrode exhibited a dual character allowing a double application in IBP degradation process and its control.

Silver-functionalized carbon nanofiber composite electrodes for ibuprofen detection

The aim of this study is to prepare and characterize two types of silver-functionalized carbon nanofiber (CNF) composite electrodes, i.e., silver-decorated CNF-epoxy and silver-modified natural zeolite-CNF-epoxy composite electrodes suitable for ibuprofen detection in aqueous solution. Ag carbon nanotube composite electrode exhibited the best electroanalytical parameters through applying preconcentration/differential-pulsed voltammetry scheme.

Copper-decorated carbon nanotubes-based composite electrodes for nonenzymatic detection of glucose

The aim of this study was to prepare three types of multiwall carbon nanotubes (CNT)-based composite electrodes and to modify their surface by copper electrodeposition for nonenzymatic oxidation and determination of glucose from aqueous solution. Copper-decorated multiwall carbon nanotubes composite electrode (Cu/CNT-epoxy) exhibited the highest sensitivity to glucose determination.