This study provides information about the analytical technique (Differential Pulse Voltammetry), the substances being analyzed (Paracetamol and Omnipaque), the type of electrode used (Boron-Doped Diamond Electrode), and the diverse applications of the method to different sample types (Natural Tomato, Carrot, Cucumber Juices, and Wastewater). Analytical methods have been developed for the individual determination of PCM and OMP, as well as for the simultaneous determination of these analytes with other pharmaceutical and biologically active compounds. Voltammetric studies allowed us to have well-defined oxidation peaks at distinct potentials of OMP (E = 0.5 V/SCE) and PCM (E = 0.7 V/SCE). Under optimized conditions, well-defined quantities of OMP and PCM, introduced simultaneously by metered additions, gave linear responses in concentration ranges of 259.8 - 467.2 \(\mu\)M for OMP and 58.73 - 116.3 \(\mu\)M PCM. The detection limits obtained are 7.23 \(\mu\)M and 3.6 \(\mu\)M respectively for OMP and PCM with recovery rates be- tween 85.8% \( \pm\) 0.1% and 92.6% \( \pm\) 0.1% for OMP and between 99.9% \( \pm\) 0.1% and 101.2% \( \pm\) 0.4% for the PCM. This technique has been successfully used to simultaneously detect these pharmaceuticals in these complex environments. It allows recovery of OMP and PCM respectively up to 97.5% \( \pm\) 0.0% and 91.6% \( \pm\) 0.3% in tomato juice; 100.0% \( \pm\) 0.0% and 95.2% \( \pm\) 0.2% in carrot juice; 101.4% \( \pm\) 0.1% and 97.3% \( \pm\) 0.3% in cucumber juice; 100.1% \( \pm\) 0.9% and 100.9% \( \pm\) 0.1% in wastewater. The relevance of this technique for the simultaneous detection of OMP and PCM in tomato, carrot, cucumber juices and in waste water can be studied in the context of the contamination of certain fruits and vegetables by the substances organic pharmaceuticals released into the environment without prior treatment. The results obtained allow us to conclude that DPV can be used with many advantages for the quantitative determination of these drugs, alone or in combination, as they are commonly found in pharmaceutical formulations.
Persistent organic pollutants such as pharmaceuticals (iohexol and paracetamol) released into the environment is an environmental problem. Thus our objective is to propose an effective and less expensive method for the determination of their concentrations in the environment. In this work the detection and quantification of pharmaceuticals (iohexol and paracetamol) were performed using cyclic voltammetry and differential pulse voltammetry (DPV). The anode used is a boron-doped diamond electrode (BDD) modified with gold particles (Au-BDD). The characterization of the Au-BDD electrode surface by scanning electron microscopy coupled to energy dispersive spectroscopy and by the electrochemical method (cyclic voltammetry) showed the presence of gold particles uniformly distributed on the anode surface. DPV method allowed to obtain two calibration curves for iohexol and paracetamol concentrations ranging respectively from 4 µM to 67.42 µM and from 0.8 µM to 22.943 µM. The limits of detection are respectively 1.13 µM and 0.045 µM for iohexol and paracetamol. These results show that the presence of gold particles on the anode surface improved the detection of paracetamol. These pharmaceuticals were detected in an ionic environment and it was noted that the interference phenomenon was very negligible during the detection of these two pharmaceuticals. This shows that our anode can be used to determine PCM and IHX concentrations in highly charged media.
This work aimed to determine the voltammetric charges at the electrode / electrolytic solution interface of the IrO2, PtOx and IrO2-PtOx electrodes. The scanning electron microscope characterization (SEM) showed the presence of the IrO2 and PtOx coating deposited on titanium supports. Also, this characterization revealed that the surface of the prepared electrodes is porous and rough. The cyclic voltammetry measurements allowed to show that the voltammetric charge is high at low scan rates. This result is due to the accessibility of the internal and external surfaces of prepared electrodes by electrolytic solution. In contrast, for the high scan rates, only the external (geometric) surface is in touch with the electrolyte. The voltammetric charge decreases when the pH of electrolyte increases. Regardless of the electrolytic solution the voltammetric charges increases in the order: PtOx < IrO2 < PtOx-IrO2. In the absence of free protons (KClO4 and KOH medium), the electrolyte diffuses inside the pores of the deposit regardless of its composition. Thus, all our electrodes have a large number of internal active sites. This study revealed that the processes which take place at the electrode / electrolyte interface are complex. These processes depend on several factors including the composition of the deposit, the proton concentration, etc. The linear correlations between the total voltammetric charge (q*tot) and the total capacitance (Ctot) show that they can be used to represent the extension of the electrochemically active surface.
This study investigated the electrochemical behavior of iohexol in its commercial formulation omnipaque on a boron-doped diamond electrode using cyclic voltammetry and chronoamperometry. The dependence of the anodic peak current density vs. iohexol concentration is linear and can be applied to the determination of the substrate concentration in environmental samples and pharmaceuticals. The iohexol electrooxidation on boron-doped diamond electrode is diffusion-controlled process and proceed via two ways: a direct electron transfers at the surface of boron-doped diamond electrode and an indirect oxidation mediated by in situ oxidative species. The iohexol electrooxidation in pH range from 2 to 6 includes exchange of 4 electrons and 1 proton, at pH superior to 6 it includes an exchanged of 2 electrons and 1 proton. The values of activation energy, anodic transfer coefficient, heterogenous rate constant, diffusion coefficient and the catalytic rate constant were 14.164 kJ mol-1, 0.428, 1.06 s-1, 4.47 cm2 s-1 and 3.61 M-1 s-1 respectively. It appears from those results that, on our electrode, for the high potential scan rates, few actives sites mainly those located at the electrode surface are involved in the iohexol oxidation process. As the potential scan rate decreases, more actives sites are involved in the process.
Lead, even in low concentrations, can be dangerous and toxic to humans and their environment. Due to the toxicity of this metal, an electroanalytical method has been developed for the direct quantitative determination of Pb2+. The Pb2+ detection was performed using Differential Pulse Anodic Stripping Voltammetry. The quantification of Pb2+ by these electrochemical methods was carried out on a boron-doped diamondmicro electrode in HNO3 medium (0.01 M). This work made it possible to efficiently detect lead with a detection limit equal to 0.052 μM and a quantification limit equal to 0.173 μM. This method made it possible to selectively detect and quantify the Pb2+ in the presence of other metals such as Cd2+ and Cu2+. In the presence of other metals, a recovery rate of 94.53% was observed. This value is close to the recovery rate obtained (98.6%) when the Pb2+ is alone in electrolyte.
The environment pollution, in particular that of the aquatic environment, by wastewater is a reality because it is discharged for the most part without treatment. The presence of pharmaceutical pollutants such as paracetamol in these waters can constitute a risk to human health. The objective of this work is to study the electrochemical oxidation of paracetamol using cyclic voltammetry on the boron doped diamond (BDD) anode and boron doped diamond modified by gold particles (Au-BDD) anode. The Au-BDD electrode was obtained by modifying the surface of BDD with gold particles. This was done by electrodeposition (chronoamperometry) in 0.5 M HAuCl4 and 0.1 M H2SO4 using a three pulse nucleation and growth process. Physical characterization with Scanning Electron Microscopy coupled with Dispersive Energy spectroscopy has shown that the Au-BDD surface presents asperities with the presence of microparticles and nanoparticles. The electrochemical characterization made in three electrolytic solutions (H2SO4, NaOH and KClO4) showed that Au-BDD has a high electroactivity domain than that of BDD. The study of the Benzoquinone-hydroquinone redox couple has shown a quasi-reversible character of these two anodes. It also revealed that Au-BDD has a more accentuated metallic character than BDD. The voltammetric measurements made it possible to show that the paracetamol oxidation is limited by the transport of material on each anode. This oxidation is characterized by the presence of an anodic peak in the support electrolytes stability domain. The paracetamol oxidation is rapid on Au-BDD than on BDD in the various medium explored, thus showing that Au-BDD is more efficient than BDD for the paracetamol oxidation by electrochemical means.
This work used Boundiali and Man clays to eliminate methyl orange in an aqueous medium. These clays were activated with hydrochloric acid and then characterized by scanning electron microscopy, X-ray diffractogram, Brunauer–Emmett–Teller (BET) method, and zero charge pH. Methyl orange concentration was monitored during adsorption using a UV-visible spectrophotometer. Characterization showed that the clays have many micropores, mesopores, and few macropores. The specific surface areas of these clays are equal to 39,084 m2 g-1 and 39,722 m2 g-1 for Boundiali and Man clays, respectively. These clays are composed of kaolinite, illite, and quartz. They have non-uniform morphologies and display irregularly shaped flaky particles of different sizes. The surface pH of Boundiali clay is neutral, while Man clay's is essential. Adsorption of methyl orange on these clays conforms to pseudo 2nd order kinetics with 60 minutes as the equilibrium time. Adsorption is favorable in acidic media and spontaneous at room temperature with both types of clay. The Boundiali clay has an adsorption capacity of 40.486 mg g-1, and the Man clay has an adsorption capacity of 38.610 mg g-1.
Abstract This study showed that the oxidation of rhodamine B by the Fenton process is a very fast method because the reaction takes place within the first 20 minutes. The mixture of Fe 2+ and H 2 O 2 produces hydroxide radicals responsible for the degradation of rhodamine B. The study of pH influence on the rhodamine B oxidation reveals that for maximum oxidation of rhodamine B, the pH must be less than or equal to 2. For pH > 2, there is a decrease in rhodamine B oxidation. This is due to side reactions that occur if the concentration of Fe 2+ is high. This reduces the amount of oxidized rhodamine B. We note that the oxidation of rhodamine B is faster for low concentrations than for high concentrations of rhodamine B. According to our results, for a maximum oxidation of 5 mg / L of rhodamine, it takes 8.4.10 −4 mg / L of Fe 2+ , 3.10 −3 M of H 2 O 2 and pH = 2. This work also showed that the presence of inorganic ions strongly slows down the rate of degradation of rhodamine in the following order: Cl − ˂ NO 3 − ˂ SO 4 2− ˂ PO 4 3 − .
In recent years, the presence of drug residues in water has become a major environmental issue. Among these pollutants is amoxicillin. Our aim is to propose effective methods for decontaminating wastewater containing amoxicillin. This study was carried out using the chemical oxygen demand method. This work has shown that hydroxyl radicals can effectively degrade amoxicillin. The rate of hydroxyl radical production from hydrogen peroxide and iron (II) ions increases in the presence of sunlight. Amoxicillin oxidation is optimal at a pH of 3 and a [H2O2]/[Fe2+] ratio of 13.33. Amoxicillin degradation is faster at low concentrations than at high concentrations. The oxidation of amoxicillin by photo-Fenton results in degradation rates of up to 99%. A study of the adsorption of amoxicillin on copper oxides showed that amoxicillin adsorbs weakly to the amoxicillin surface, with an adsorption rate of 17%. However, in the presence of amoxicillin, hydrogen peroxide and sunlight, degradation rates of up to 99% were obtained. This work has shown that the degradation of amoxicillin is better with solar photo Fenton and solar photocatalysis in the presence of copper oxide than with the Fenton process.
The platinum anode modified by metal oxides electrodes degrades Abidjan wastewater which contains a high concentration of Cl-. During this degradation process, the organic polluants are oxidized, O2 and Cl2 are produced. The purpose of this study is to contribute to the understanding of these reaction mechanisms by studying the kinetics of O2 and Cl2 evolution at neutral pH on Pt. The study was performed by interpreting the voltammograms and Tafel slopes obtained. The voltammetric measurements were carried out using an Autolab Potentiostat from ECHOCHEMIE (PGSTAT 20) connected by interface to a computer. Pt electrode was prepared on titanium (Ti) substrate by thermal decomposition techniques at 400°C. The characterization of the surface of the prepared electrode by scanning electron microscopy and X-ray photoelectron spectrometry showed the presence of platinum on its surface. The results obtained show that the OH· are adsorbed on the active sites of Pt. Then they react to form PtO. Then by reaction between the surface oxygen and PtO, O2 is produced and the active sites are regenerated. In the presence of low Cl- concentration, there is a competition between the Cl2 and O2 evolution reactions. However, Cl2 only is produced for high Cl- concentrations. The kinetics of the evolution reaction of chlorine increases with the concentration of Cl- and remains constant for concentrations greater than 0.5 M. This study also showed that the chlorine reduction reaction produced in solution is a diffusion-controlled reaction for low scan rates.
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