scholarly journals Fabrication of electrochemical biosensors for the determination of phenolic compounds by experimental and computational methods

2018 ◽  
Author(s):  
◽  
Kwanele Winterose Kunene
Keyword(s):  
Electron Microscopy ◽  
Cyclic Voltammetry ◽  
Computational Methods ◽  
Limit Of Detection ◽  
Electrochemical Behaviour ◽  
Zno Nanorods ◽  
Experimental Results ◽  
Bisphenol S ◽  
Experimental Conditions

The polyphenolic compounds of interest, bisphenol A (BPA) and its analogue bisphenol S (BPS) used in the plastic industry to manufacture baby bottles and beverage containers, were used in this study. They are generally used in the manufacture of polycarbonates, epoxy resins and unsaturated polystyrene resins. There is a growing concern in the public and scientific community about these organic compounds due to their endocrine disrupting activity and negative toxic impact on the wildlife. This has encouraged scientists to embark on research to find a sensitive and selective technique that will adequately determine these compounds even in trace amounts. The experimental research strategy adopted in this work was supported by computational methods. This work was conducted in two stages; Firstly, a sensitive EC biosensor was developed using a carbon screen printed electrode fabricated with the combination of silver doped zinc oxide nanoparticles with multiwalled carbon nanotubes (MWCNTs) and laccase enzyme. The EC behaviour of BPA towards the fabricated biosensor was investigated using cyclic voltammetry and differential pulse voltammetry under optimum experimental conditions. Secondly, a novel and selective PEC sensor was developed for the first time to detect BPS based on the vertically aligned ZnO nanorods (ZnO NRs) with a molecularly imprinted polypyrrole (PPy). Amperometric, cyclic voltammetry and impedance spectroscopy were used for the investigation of the photo induced electrochemical behaviour of BPS. Different characterisation techniques such as ultra-violet visible spectroscopy, fourier transform infrared spectroscopy, scanning electron microscopy, transmission electron microscopy, photoluminescence, Raman spectroscopy, grazing incidence X-ray diffraction and diffuse reflectance were used to characterize the synthesized nanostructures. Results revealed that the fabricated EC and PEC sensors exhibited good catalytic activity towards the determination of BPA and BPS respectively, in samples extracted from plastic water bottles. For the EC method, a low detection limit of 0.08 μM for BPA in a linear range 0.5 to 2.99 µM was detected. However, in the case of BPS, a highly selective PEC method was attained linearly ranging from 2.5 to 12.5 µM with a much higher limit of detection of 0.7 μM. Experimental results were further supported computationally for a better understanding of the optical properties of ZnO NRs-polypyrrole complex. Computational results were in good agreement with experimental results.

Electrochemical Behaviour of 3-Pyridyl-N,N-bis[(8-quinolyl)amino]methane

1993 ◽  
Vol 58 (6) ◽  
pp. 1279-1284
Author(s):  
Angeles Loeches ◽  
Carmen Teijeiro ◽  
Dolores Marín
Keyword(s):  
Cyclic Voltammetry ◽  
Limit Of Detection ◽  
Electrochemical Behaviour ◽  
Differential Pulse ◽  
Differential Pulse Polarography ◽  
Reduction Mechanism ◽  
Pulse Polarography ◽  
Dc Polarography ◽  
The Waves

3-Pyridyl-N,N-bis[(8-quinolyl)amino]methane was studied by DC polarography, coulometry, cyclic voltammetry and differential pulse polarography in a system comprising Britton-Robinson buffer and 15 vol.% ethanol at pH 7.0. The nature of the waves was investigated, and the reduction mechanism is suggested. DPP was also used for a quantitative determination of the substance, and a limit of detection of 3 μmol l-1 was obtained.

On the electroreduction mechanism of halobenzenes: Detection of intermediates in reduction of monohalobenzenes

1989 ◽  
Vol 54 (4) ◽  
pp. 900-910 ◽  
Author(s):  
Juan Casado ◽  
Iluminada Gallardo
Keyword(s):  
Cyclic Voltammetry ◽  
Electrochemical Behaviour ◽  
Experimental Results ◽  
Disk Electrode ◽  
Rotating Ring Disk Electrode ◽  
Mercury Cathode

Experimental results from electrochemical behaviour of halobenzenes in DMF at a mercury cathode are used to discuss alternative mechanisms of reduction. Intermediates of these mechanisms, such as phenyl anion, phenylmercury radical and phenylmercury cation have been detected at the electrode by using cyclic voltammetry and a rotating ring-disk electrode.

scholarly journals Determination of cobalt in water samples by atomic absorption spectrometry after pre-concentration with a simple ionic liquid-based dispersive liquid-liquid micro-extraction methodology

2010 ◽  
Vol 8 (3) ◽  
pp. 617-625 ◽  
Author(s):  
Hossein Abdolmohammad-Zadeh ◽  
Elnaz Ebrahimzadeh
Keyword(s):  
Ionic Liquid ◽  
Atomic Absorption Spectrometry ◽  
Atomic Absorption ◽  
Water Samples ◽  
Limit Of Detection ◽  
Absorption Spectrometry ◽  
Experimental Conditions ◽  
Flame Atomic Absorption ◽  
Relative Standard

AbstractA rapid dispersive liquid-liquid micro-extraction (DLLME) methodology based on the application of 1-hexylpyridinium hexafluorophosphate [C6py][PF6] ionic liquid (IL) as an extractant solvent was applied for the pre-concentration of trace levels of cobalt prior to determination by flame atomic absorption spectrometry (FAAS). 1-Phenyl-3-methyl-4-benzoyl-5-pyrazolone (PMBP) was employed as a chelator forming a Co-PMBP complex to extract cobalt ions from aqueous solution into the fine droplets of [C6py][PF6]. Some effective factors that influence the micro-extraction efficiency include the pH, the PMBP concentration, the amount of ionic liquid, the ionic strength, the temperature and the centrifugation time which were investigated and optimized. In the optimum experimental conditions, the limit of detection (3s) and the enrichment factor were 0.70 µg L−1 and 60, respectively. The relative standard deviation (RSD) for six replicate determinations of 50 µg L−1 Co was 2.36%. The calibration graph using the pre-concentration system was linear at levels 2–166 µg L−1 with a correlation coefficient of 0.9982. The applicability of the proposed method was evaluated by the determination of trace amounts of cobalt in several water samples.

scholarly journals Cerimetric determination of simvastatin in pharmaceuticals based on redox and complex formation reactions

2018 ◽  
Vol 33 (2) ◽  
pp. 21
Author(s):  
Kanakapura Basavaiah ◽  
Okram Zenita Devi
Keyword(s):  
Limit Of Detection ◽  
Reference Method ◽  
Standard Addition ◽  
Molar Absorptivity ◽  
Experimental Conditions ◽  
Spectrophotometric Methods ◽  
Fixed Quantity ◽  
Bulk Drug ◽  
Student’S T

Two sensitive spectrophotometric methods are described for the determination of simvastatin (SMT) in bulk drug and in tablets. The methods are based on the oxidation of SMT by a measured excess of cerium (IV) in acid medium followed by determination of unreacted oxidant by two different reaction schemes. In one procedure (method A), the residual cerium (IV) is reacted with a fixed concentration of ferroin and the increase in absorbance is measured at 510 nm. The second approach (method B) involves thereduction of the unreacted cerium (IV) with a fixed quantity of iron (II), and the resulting iron (III) is complexed with thiocyanate and the absorbance measured at 470 nm. In both methods, the amount of cerium (IV) reacted corresponds to SMT concentration. The experimental conditions for both methods were optimized. In method A, the absorbance is found to increase linearly with SMT concentration (r = 0.9995) whereas in method B, the same decreased (r = -0.9943). The systems obey Beer’s law for 0.6-7.5 and 0.5-5.0 μg mL-1 for method A and method B, respectively. The calculated molar absorptivity values are 2.7 X 104 and 1.06 X 105 Lmol-1 cm-1, respectively; and the corresponding sandel sensitivity values are 0.0153 and 0.0039μg cm-2, respectively. The limit of detection (LOD) and quantification (LOQ) are reported for both methods. Intra-day and inter-day precision, and accuracy of the methods were established as per the current ICH guidelines. The methods were successfully applied to the determination of SMT in tablets and the results were statistically compared with those of the reference method by applying the Student’s t-test and F-test. No interference was observed from the common excipients added to tablets. The accuracy and validity of the methods were further ascertained by performing recovery experiments via standard addition procedure.

scholarly journals An Electrochemical Sensor Based On Graphite Electrode Modified With Silica Containing 1-N-Propyl-3-Methylimidazolium Species For Determination Of Ascorbic Acid

2019 ◽  
Vol Vol. 14, No.1 ◽  
pp. 5-14 ◽  
Author(s):  
Anastasiya Tkachenko ◽  
Mykyta Onizhuk ◽  
Oleg Tkachenko ◽  
Leliz T. Arenas ◽  
Edilson V. Benvenutt ◽  
...  
Keyword(s):  
Ascorbic Acid ◽  
Cyclic Voltammetry ◽  
Electrochemical Sensor ◽  
Electrochemical Impedance ◽  
Limit Of Detection ◽  
Pharmaceutical Formulations ◽  
Differential Pulse ◽  
Long Term Stability ◽  
Diffusion Limited

In the present study, an electrochemical sensor based on the electrode (SiMImCl/C) consisting of graphite and silica, grafted with 1-n-propyl-3-methylimidazolium chloride was used for ascorbic acid (AA) quantification in pharmaceuticals and food formulations. Cyclic voltammetry and electrochemical impedance spectroscopy were applied for electrochemical characterization of the SiMImCl/C electrode. The cyclic voltammetry study revealed that the oxidation of AA on this electrode is an irreversible process, realized by adsorption and diffusion limited step. The differential pulse voltammetry was applied to develop a procedure for the AA determination. The linear range was found to be 0.3–170 μmol L-1 and the limit of detection – 0.1 μmol L-1. The proposed SiMImCl/C electrode has long term stability and does not show electrochemical activity towards the analytes, which commonly coexist with AA. The sensor was successfully used for quantification of AA in food and pharmaceutical formulations.

scholarly journals Interaction between Amorphous Zirconia Nanoparticles and Graphite: Electrochemical Applications for Gallic Acid Sensing Using Carbon Paste Electrodes in Wine

Nanomaterials ◽  
2020 ◽  
Vol 10 (3) ◽  
pp. 537 ◽  
Author(s):  
Chrys. O. Chikere ◽  
Nadimul Haque Faisal ◽  
Paul Kong-Thoo-Lin ◽  
Carlos Fernandez
Keyword(s):  
Gallic Acid ◽  
Limit Of Detection ◽  
Electrochemical Behaviour ◽  
Differential Pulse ◽  
White Wine ◽  
Zro2 Nanoparticles ◽  
Carbon Paste ◽  
X Ray ◽  
Zirconia Nanoparticles

Amorphous zirconium oxide nanoparticles (ZrO2) have been used for the first time, to modify carbon paste electrode (CPE) and used as a sensor for the electrochemical determination of gallic acid (GA). The voltammetric results of the ZrO2 nanoparticles-modified CPE showed efficient electrochemical oxidation of gallic acid, with a significantly enhanced peak current from 261 µA ± 3 to about 451 µA ± 1. The modified surface of the electrode and the synthesised zirconia nanoparticles were characterised by scanning electrode microscopy (SEM), Energy-dispersive x-ray spectroscopy (EDXA), X-ray powdered diffraction (XRD) and Fourier-transform infrared spectroscopy (FTIR). Meanwhile, the electrochemical behaviour of GA on the surface of the modified electrode was studied using differential pulse voltammetry (DPV), showing a sensitivity of the electrode for GA determination, within a concentration range of 1 × 10−6 mol L−1 to 1 × 10−3 mol L−1 with a correlation coefficient of R2 of 0.9945 and a limit of detection of 1.24 × 10−7 mol L−1 (S/N = 3). The proposed ZrO2 nanoparticles modified CPE was successfully used for the determination of GA in red and white wine, with concentrations of 0.103 mmol L−1 and 0.049 mmol L−1 respectively.

Use of the curvature method to determine the misfit stress of epitaxial semiconducting systems: the case of samples thinned for TEM observation.

2003 ◽  
Vol 795 ◽  
Author(s):  
A. Ponchet ◽  
M. Cabié ◽  
L. Durand ◽  
M. Rivoal ◽  
A. Rocher
Keyword(s):  
Electron Microscopy ◽  
Mechanical Characteristics ◽  
Substrate Thickness ◽  
Element Calculation ◽  
Experimental Conditions ◽  
Misfit Stress ◽  
Reliable Determination ◽  
Substrate Side ◽  
Transmission Electron

ABSTRACTThe curvature method which allows to measure the stress in epitaxial layers has been adapted to transmission electron microscopy observations. The samples thinned by the substrate side present some particular mechanical characteristics. The ratio between the substrate thickness and the layer thickness should be taken into account. The experimental conditions allowing a reliable determination of the stress have been established. A finite element calculation has been used to show that the dimensions of the area where the measure is performed can not systematically be neglected. This method has been applied to the semiconducting systems Ga1-xInxAs/GaAs and Ga1-xInxAs/InP.

A Facile In-Situ Development of L-Valine Film onto the Surface of Carbon Paste Electrode Towards the Detection of Environmentally Hazardous 4-Amino Phenol

2019 ◽  
Vol 0 (0) ◽  
Author(s):  
T. Venu Gopal ◽  
Tukiakula Madhusudana Reddy ◽  
P. Shaikshavali ◽  
G. Venkataprasad ◽  
P. Gopal
Keyword(s):  
Cyclic Voltammetry ◽  
Carbon Paste Electrode ◽  
Electrochemical Impedance ◽  
Limit Of Detection ◽  
Small Scale ◽  
Carbon Paste ◽  
Relative Standard ◽  
Paste Electrode

Abstract A small scale of environmentally hazardous 4-aminophenol can show significant impact on human health. Hence, in the present work, we have designed L-Valine film (Vf) modified carbon paste electrode (Vf/CPE) for the determination of 4-aminophenol. Herein, a facile in-situ L-Valine film was developed by electrochemical polymerization method onto the surface of bare carbon paste electrode (BCPE) with the help of cyclic voltammetry (CV) technique. A two-folds of electrochemical peak current enhancement was achieved at Vf/CPE in comparison with BCPE towards the determination of 4-aminophenol in optimum pH 7.0 of phosphate buffer solution (PBS). This was achieved due to the large surface area and conductive nature of Vf/CPE, which was concluded through the techniques of cyclic voltammetry and electrochemical impedance spectroscopy (EIS). The effect of pH of buffer and scan rate studies were successfully studied. Morphological changes of BCPE and Vf/CPE was studied with the help of scanning electron microscopy (SEM). The formation of Vf on CPE was also analyzed by Fourier transform infrared (FTIR) spectra. Under the optimized conditions, the limit of detection (LOD) and limit of quantification (LOQ) values of 4-aminophenol were estimated with the aid of chronoamperometry (CA) technique and was found to be 9.8 μM and 32 μM, respectively. Finally the proposed method was found to have satisfactory repeatability, reproducibility and stability results with low relative standard deviation (RSD) values.

scholarly journals A High-Response Electrochemical As(III) Sensor Using Fe3O4–rGO Nanocomposite Materials

Chemosensors ◽  
2021 ◽  
Vol 9 (6) ◽  
pp. 150
Author(s):  
Haibing Hu ◽  
Wenjie Lu ◽  
Xingnan Liu ◽  
Fancheng Meng ◽  
Jianxiong Zhu
Keyword(s):  
Electron Microscopy ◽  
Glassy Carbon ◽  
Metal Ion ◽  
Electrochemical Impedance ◽  
Limit Of Detection ◽  
Detection Methods ◽  
Experimental Conditions ◽  
Water Field ◽  
Conductive Substrates ◽  
Higher Sensitivity

Nowadays, heavy metal ion pollution in water is becoming more and more common, especially arsenic, which seriously threatens human health. In this work, we used Fe3O4–rGO nanocomposites to modify a glassy carbon electrode and selected square wave voltametric electrochemical detection methods to detect trace amounts of arsenic in water. Field emission scanning electron microscopy (FESEM) and transmission electron microscopy (TEM) showed that Fe3O4 nanoparticles were uniformly distributed on the rGO sheet, with a particle size of about 20 nm. Raman spectroscopy and electrochemical impedance spectroscopy (EIS) showed that rGO provides higher sensitivity and conductive substrates. Under optimized experimental conditions, Fe3O4–rGO-modified glassy carbon electrodes showed a higher sensitivity (2.15 µA/ppb) and lower limit of detection (1.19 ppb) for arsenic. They also showed good selectivity, stability, and repeatability.

scholarly journals Use of Dispersive Liquid-Liquid Microextraction and UV-Vis Spectrophotometry for the Determination of Cadmium in Water Samples

2014 ◽  
Vol 2014 ◽  
pp. 1-4 ◽  
Author(s):  
J. Pérez-Outeiral ◽  
E. Millán ◽  
R. Garcia-Arrona
Keyword(s):  
Water Samples ◽  
Limit Of Detection ◽  
Experimental Conditions ◽  
Cadmium Determination ◽  
A Value ◽  
Relative Standard ◽  
Potential Applicability ◽  
Dispersive Liquid Liquid Microextraction ◽  
Liquid Microextraction

A simple and inexpensive method for cadmium determination in water using dispersive liquid-liquid microextraction and ultraviolet-visible spectrophotometry was developed. In order to obtain the best experimental conditions, experimental design was applied. Calibration was made in the range of 10–100 μg/L, obtaining good linearity (R2 = 0.9947). The obtained limit of detection based on calibration curve was 8.5 μg/L. Intra- and interday repeatability were checked at two levels, obtaining relative standard deviation values from 9.0 to 13.3%. The enrichment factor had a value of 73. Metal interferences were also checked and tolerable limits were evaluated. Finally, the method was applied to cadmium determination in real spiked water samples. Therefore, the method showed potential applicability for cadmium determination in highly contaminated liquid samples.

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