This paper reports on the use of electrochemical impedance spectroscopy (EIS) for analytical determination of paraquat herbicide at a silver electrode. The electrochemical technique was applied to ...aqueous solution, at pH 7.0, containing different concentrations of paraquat. The impedance measurements were carried out in the frequency range from 100 mHz to 100 KHz at a potential of 0.0 mV versus Ag/AgCl. The Nyquist plots were modeled with a Randle equivalent circuit, by identifying the charge transfer resistance as the relevant concentration dependent parameter. The silver surface adsorbs paraquat and the transfer process is controlled by diffusion. The response of the working electrode was attributed to the electron-exchange mechanism at the electrode–contact interface and the ion exchange at the electrode–solution interface. The proposed methodology offers good repeatability (RSD = 1.03%) with (n = 8) and impedimetric response to paraquat in the range from 1.0 × 10−14 to 8.0 × 10−4 mol L−1. The detection limit (DL, 3σ) and quantification limit (QL, 10σ) were 7.37 × 10−16 mol L−1 and 24.59 × 10−16 mol L−1 respectively. The method was satisfactorily applied to determine paraquat in milk and tomato samples.
•A silver electrode was used to determine paraquat using impedance spectroscopy (EIS).•The influence of the variables which involved the EIS measurement was investigated.•The silver electrode was tested to determine paraquat in tomato and milk samples.•The methodology is effective for the detection of paraquat in natural samples.
The purpose of this paper is the modification of a carbon paste electrode (CPE) with activated carbon synthesized from date stones using a pyrolysis system followed by physical activation. This ...material has the advantage of very low cost and facilitates charge transfer. The modified electrode was used for electrocatalysis and determination of catechol. A series of analyses and tests were carried out to demonstrate the nature, the surface functional groups and even the porosity of the resulting product. The activated carbon exhibited remarkable electrocatalytic activity toward catechol oxidation. The electron transfer coefficient, surface coverage and number of electrons for catechol oxidation at the surface of the AC-CPE were determined using electrochemical approaches. Subsequently, a sensitive and convenient electrochemical method was proposed for catechol analysis. The linear range is between 1.0 × 10
−6
and 1.0 × 10
−3
mol L
−1
with a correlation coefficient of 0.993. The limit of detection is as low as 4.8 × 10
−8
mol L
−1
. Finally, this novel method was employed to determine the catechol in tap water, green, black and peach teas, and in coffee samples.
The purpose of this paper is the modification of a carbon paste electrode (CPE) with activated carbon synthesized from date stones using a pyrolysis system followed by physical activation.
•Valorization of the waste product of Phoenix dactylifera L. (Date stone) was conducted.•The Green synthesis of AgNPs was carried out using Phoenix dactylifera L. extract.•GAgNPs was used to modify ...carbon paste for electrochemical detection of ornidazole.
Over the past few decades, nanotechnology evolved into a significant, interdisciplinary research field on a global scale. Due to their extraordinary physicochemical, optical, and biological qualities, noble metal nanoparticles like gold, silver, palladium, and platinum are widely used in a variety of industrial and pharmaceutical procedures. In this study, a quick, low-cost, and environmentally friendly approach was used to create GAgNPs. Without using hazardous chemical substances, GAgNPs were produced using Phoenix dactylifera seeds extract as a reducing and stabilizing agent. The synthesized GAgNPs were characterized by UV-Visble, X-ray diffraction, and scanning electron microscopy. The presence of GAgNPs confirmed by the appearance of peak at 420 nm employing UV-Vis method, also affirmed by X-ray diffraction pattern, and the calculated size was about 28.72 nm. The electrochemical activity of GAgNPs was investigated through the elaboration of carbon paste-based sensor for the determination of ornidazole. The GAgNPs modified carbon paste electrode displayed a linear concentration range from 1.0 × 10−3 mol L−1 to 5.0 × 10−5 mol L−1 with a detection limit and quantification limit of 3.8 × 10−6 mol L−1 and 1.2 × 10−5 mol L−1, respectively. The proposed sensor was used for ornidazole analysis in milk samples, providing satisfactory recoveries of 105.7% and 102.7% with RSD below 4%.
In this study, a modified carbon paste electrode with silver particles (Ag–CPE) was used for ofloxacin (OFL) detection with enhanced over-potential for low concentrations. The incorporation of silver ...particles on carbon paste was confirmed by scanning electron microscopy. Electrochemical behavior of ofloxacin at carbon paste electrode (CPE) and Ag–CPE was studied using cyclic voltammetry, chronoamperometry and electrochemical impedance spectroscopy. The OFL interaction with Ag+ was derived from the oxidation of silver during anodic scan has been investigated under different conditions. The strong binding affinity of Ag+ with 1.0 × 10−5 M OFL resulted in the upward shift of the OFL potential, which shifted potential from 0.85 to 0.95 V. The modification of carbon paste electrode by silver microparticles has enhanced the oxidation current with over-potential of OFL at low concentrations without a decrease of the current. The influence of the sweeping potential range on OFL oxidation was optimized. The calibration curve for ofloxacin at Ag–CPE is linear in the range from 4.0 × 10−6 to 1.0 × 10−3 M, and the detection limit was 9.47 × 10−7 M. Possible effects of inorganic ions and organic substances were investigated but did not cause any significant interferences. Furthermore, the repeatability, reproducibility, and stability of the present sensor were done with satisfactory results. The proposed method was successfully applied to OFL determination in tap water samples.
The electrochemical impedance spectroscopy (EIS) has been used to study the interaction between paraquat and carbon modified by silver (AgCPE) and silver particles‐impregnated natural phosphate ...(Ag/NPhCPE). This study was developed using spectrophotometry (UVVis) and infrared spectroscopy. The resulting interaction was controlled by adsorption at lower concentration (≤1.0×10−5 mol L−1) and by diffusion in the opposite case. Both electrodes are used to determining paraquat with a low detection limit (<1.0×10−12 mol L−1). The precision expressed as relative standard deviation RSD for the concentration level 1.0×10−5 mol L−1 of paraquat, (n=8) were 0.93 % and 1.1 % for Ag/NPhCPE and AgCPE respectively.
A simple, selective and sensitive electrochemical method is described for the determination of different aldehydes at glassy carbon electrode using electrochemical impedance spectroscopy (EIS). The ...measurements were performed after their derivatization with 2,4-dinitrophenylhydrazine (DNPH) in acidic medium. The impedance measurements were investigated in the frequency range from 100 mHz to 100 kHz at a potential of 1.0 V versus Ag/AgCl. The Nyquist plots were modeled with a Randle’s equivalent circuit. The charge transfer resistance was identified as the dependent parameter on relevant concentration of aldehydes (determined as their hydrazones). Under the optimized conditions, the linearity was established over the concentration range of 1000–0.05 μmol L−1. The limits of detection (LODs) obtained were from 0.097 to 0.0109 μmol L−1. Finally, the developed method has been applied to the determination of aldehydes in drinking water, orange juice and apple vinegar samples with relative standard deviations (RSDs) < 3.1% and acceptable recovery rate (around of 80%).
In the present work, a reduced graphene oxide/chitosan pencil electrode (rGO/CHI/PGE) was successfully synthesized for the analysis of flubendiamide (FBD). The graphene oxide (GO) was reduced by a ...quick, efficient, and green electrochemical method without the use of any reducing chemicals. Structural and morphological analyses of the rGO/CHI/PGE were carried out. Under optimized parameters, the detection limit was found to be 9 nM. This developed electrochemical device was successfully used as a simple and cost-effective electrode for FBD detection in white rice samples.
We report a simple, green and cost-effective approach to synthesize high-quality reduced graphene oxide/chitosan composites for determining flubendiamide. Graphene oxide was obtained by electrochemical exfoliation of pencil using a DC supply system.
In this work, a pencil graphite electrode modified with ionic liquid and natural phosphate (PGE/IL/NPht) was manufactured for the insecticide flubendiamide (FBD) sensing in water and white rice. The ...reduction current of the FBD was linearly dependent on the concentration over the linear range of 9.0 × 10−7–5.0 × 10−5 mol L−1 (R2 = 0.997) with a limit of detection of 2.0 × 10−8 mol L−1. Possible interferences of several inorganic species such as Cu2+, Mg2+, and Na+ and pesticides such as thiamethoxam, imidacloprid, and 4-nitrophenol were also carried out. The results show that their existence has no effect on the analysis of FBD and its reduction potential is not affected. Moreover, the established sensor proved to be a viable alternative to the conventional methods for FBD detection in water and white rice even without sample cleanup.
The electrochemical reduction of paranitrophenol (4-NP) has been studied on a carbon paste electrode (CPE) modified with Clay microparticles (Clay-CPE) using cyclic and differential pulse ...voltammetry. The clay microparticles were synthesized by exploring a new source from Akrach area situated in the west north, Morocco. Physicochemical characterization of the prepared clay was carried out using X−ray diffraction spectroscopy (XRD), scanning electron microscopy (SEM), energy dispersive X−ray analysis (EDX), and Fourier transform-infrared spectroscopy (FT−IR). During electrochemical measurements, the reduction current of 4−NP was much higher at Clay−CPE in Britton Robinson buffer solution (BR, pH2). 4-NP yields a well-defined reduction peak at Epc = −0.74 V which gradually increases in height with the concentration of the analyte in the range from 1.0 × 10−5 mol L−1 to 1.0 × 10−3 mol L−1 with a detection limit (DL) of 1.50 × 10−6 mol L−1. The Clay−CPE has been used successfully for the determination of 4−NP in water samples.
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