scholarly journals Antioxidant Determination with the Use of Carbon-Based Electrodes

Chemosensors ◽  
2021 ◽  
Vol 9 (4) ◽  
pp. 72
Author(s):  
Aurelia Magdalena Pisoschi ◽  
Aneta Pop ◽  
Florin Iordache ◽  
Loredana Stanca ◽  
Liviu Bilteanu ◽  
...  
Keyword(s):  
Surface Area ◽  
Oxidation Process ◽  
Low Cost ◽  
Oxidative Enzymes ◽  
Adaptation Mechanisms ◽  
Chain Breaking ◽  
Nanomolar Range ◽  
Quench Singlet Oxygen ◽  
Carbon Based

Antioxidants are compounds that prevent or delay the oxidation process, acting at a much smaller concentration, in comparison to that of the preserved substrate. Primary antioxidants act as scavenging or chain breaking antioxidants, delaying initiation or interrupting propagation step. Secondary antioxidants quench singlet oxygen, decompose peroxides in non-radical species, chelate prooxidative metal ions, inhibit oxidative enzymes. Based on antioxidants’ reactivity, four lines of defense have been described: Preventative antioxidants, radical scavengers, repair antioxidants, and antioxidants relying on adaptation mechanisms. Carbon-based electrodes are largely employed in electroanalysis given their special features, that encompass large surface area, high electroconductivity, chemical stability, nanostructuring possibilities, facility of manufacturing at low cost, and easiness of surface modification. Largely employed methods encompass voltammetry, amperometry, biamperometry and potentiometry. Determination of key endogenous and exogenous individual antioxidants, as well as of antioxidant activity and its main contributors relied on unmodified or modified carbon electrodes, whose analytical parameters are detailed. Recent advances based on modifications with carbon-nanotubes or the use of hybrid nanocomposite materials are described. Large effective surface area, increased mass transport, electrocatalytical effects, improved sensitivity, and low detection limits in the nanomolar range were reported, with applications validated in complex media such as foodstuffs and biological samples.

scholarly journals A New Method to Estimate Fuel Surface Area-to-Volume Ratio Using Water Immersion.

1998 ◽  
Vol 8 (3) ◽  
pp. 121 ◽  
Author(s):  
PM Fernandes ◽  
FC Rego
Keyword(s):  
Surface Area ◽  
Particle Density ◽  
Low Cost ◽  
Water Immersion ◽  
Volume Ratio ◽  
Adsorbed Water ◽  
General Technique ◽  
Fuel Surface ◽  
Before And After

A fast, simple, low cost and general technique for estimating fuel surface area-to-volume ratio is presented. The technique requires particle density, the determination of fuel weight before and after immersion in water and the theoretical thickness of the adsorbed water pellicle that is assumed constant. Estimates by the technique were consistent and in good agreement with published surface area-to-volume ratios for the same fuels obtained through other methods, and its performance was judged appropriate for current fire behaviour modelling needs. This water immersion technique was applied to various shrubs and trees grown in Portugal. Limitations and possibilities for improvement of the newly developed technique are discussed.

scholarly journals A New Method to Estimate Fuel Surface Area-to-Volume Ratio Using Water Immersion

1998 ◽  
Vol 8 (2) ◽  
pp. 59 ◽  
Author(s):  
PM Fernandes ◽  
FC Rego
Keyword(s):  
Surface Area ◽  
Particle Density ◽  
Low Cost ◽  
Water Immersion ◽  
Volume Ratio ◽  
Adsorbed Water ◽  
General Technique ◽  
Fuel Surface ◽  
Before And After

A fast, simple, low cost and general technique for estimating fuel surface area-to-volume ratio was developed. It requires the knowledge of particle density, the determination of fuel weight before and after immersion in water, and theoretical thickness of the adsorbed water pellicle that is assumed constant. Estimates by the technique were consistent and in good agreement with published surface area-to-volume ratios for the same fuels obtained through commonly used methods, and its performance is judged appropriate for the current fire behaviour modeling needs. The water immersion technique was applied to five common shrub species in Portugal. Limitations and possibilities for improvement of the newly developed technique are discussed.

scholarly journals USO DA VOLTAMETRIA CÍCLICA E DA ESPECTROSCOPIA DE IMPEDÂNCIA ELETROQUÍMICA NA DETERMINAÇÃO DA ÁREA SUPERFICIAL ATIVA DE ELETRODOS MODIFICADOS À BASE DE CARBONO

2014 ◽  
Vol 39 (1) ◽  
pp. 49
Author(s):  
L. L. de Souza ◽  
C. A. L. G. de O. Forbicini
Keyword(s):  
Ion Exchange ◽  
Surface Area ◽  
Glassy Carbon ◽  
Electrochemical Cell ◽  
Active Surface ◽  
Carbon Electrodes ◽  
Active Surface Area ◽  
Surface Areas ◽  
Carbon Based

Carbon-based electrodes as well the ion exchange electrodes among others have been applied mainly in the treatment of industrial effluents and radioactive wastes. Carbon is also used in fuel cells as substrate for the electrocatalysts, having high surface area which surpasses its geometric area. The knowledge of the total active area is important for the determination of operating conditions of an electrochemical cell with respect to the currents to be applied (current density). In this study it was used two techniques to determine the electrochemical active surface area of glassy carbon, electrodes and ion exchange electrodes: cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS). The experiments were carried out with 0.1 mol.L-1 KNO3 solutions in a three-electrode electrochemical cell: carbon-based working electrode, platinum auxiliary electrode and Ag/AgCl reference electrode. The glassy carbon and porous carbon electrodes with geometric areas of 3.14 x 10-2 and 2.83 х 10-1 cm2, respectively, were used. The ion exchange electrode was prepared by mixing graphite, carbon, ion exchange resin and a binder, and this mixture was applied in three layers on carbon felt, using a geometric area of 1.0 cm2 during the experiments. The capacitance (Cd) of the materials was determined by EIS using Bode diagrams. The value of 172 μF.cm-2 found for the glassy carbon is consistent with the literature data (~200 μF.cm-2). By VC, varying the scan rate from 0.2 to 2 mV.s-1, the capacitance CdS (S = active surface area) in the region of the electric double layer (EDL) of each material was determined. By EIS, the values of Cd, 3.0 x 10-5 μF.cm-2 and 11 x 103 μF.cm-2, were found for the porous carbon and ion exchange electrodes, respectively, which allowed the determination of active surface areas as 3.73 x 106 cm2 and 4.72 cm2. To sum up, the combined use of EIS and CV techniques is a valuable tool for the calculation of active surface areas of carbon-based electrodes.

Ti3C2-MXene/Bismuth Ferrite Nanohybrids for Efficient Degradation of Organic Dye and Colorless Pollutant

2019 ◽  
Author(s):  
Ayesha Tariq ◽  
M. Abdullah Iqbal ◽  
S. Irfan Ali ◽  
Muhammad Z. Iqbal ◽  
Deji Akinwande ◽  
...  
Keyword(s):  
Surface Area ◽  
Low Cost ◽  
Bismuth Ferrite ◽  
Organic Dye ◽  
Two Dimensional ◽  
Electron Hole ◽  
Photocatalytic Application ◽  
Electron Hole Pair ◽  
Pair Generation ◽  
Photocatalytic Applications

<p>Nanohybrids, made up of Bismuth ferrites/Carbon allotropes, are extensively used in photocatalytic applications nowadays. Our work proposes a nanohybrid system composed of Bismuth ferrite nanoparticles with two-dimensional (2D) MXene sheets namely, the BiFeO<sub>3</sub> (BFO)/Ti<sub>3</sub>C<sub>2</sub> (MXene) nanohybrid for enhanced photocatalytic activity. We have fabricated the BFO/MXene nanohybrid using simple and low cost double solvent solvothermal method. The SEM and TEM images show that the BFO nanoparticles were attached onto the MXene surface and in the inter-layers of two-dimensional (2D) MXene sheets. The photocatalytic application is tested for the visible light irradiation which showed the highest efficiency among all pure-BFO based photocatalysts, i.e. 100% degradation in 42 min for organic dye (Congo Red) and colorless aqueous pollutant (acetophenone) in 150 min, respectively. The present BFO-based hybrid system exhibited the large surface area of 147 m<sup>2</sup>g<sup>-1</sup>measured via Brunauer-Emmett-Teller (BET) sorption-desorption technique, and is found to be largest among BFO and its derivatives. Also, the photoluminescence (PL) spectra indicate large electron-hole pair generation. Fast and efficient degradation of organic molecules is supported by both factors; larger surface area and lower electron-hole recombination rate. The BFO/MXene nanohybrid presented here is a highly efficient photocatalyst compared to other nanostructures based on pure BiFeO<sub>3</sub> which makes it a promising candidate for many future applications.</p>

Microextraction and Chromatographic Analysis of Budesonide Epimers in Exhaled Breath Condensate

2020 ◽  
Vol 16 (8) ◽  
pp. 1032-1040
Author(s):  
Laleh Samini ◽  
Maryam Khoubnasabjafari ◽  
Mohamad M. Alimorad ◽  
Vahid Jouyban-Gharamaleki ◽  
Hak-Kim Chan ◽  
...  
Keyword(s):  
Biological Fluids ◽  
Exhaled Breath Condensate ◽  
Low Cost ◽  
Exhaled Breath ◽  
Chromatography Method ◽  
Extraction Solvent ◽  
Drug Concentrations ◽  
Dispersive Liquid Liquid Microextraction ◽  
Breath Condensate

Background: Analysis of drug concentrations in biological fluids is required in clinical sciences for various purposes. Among other biological samples, exhaled breath condensate (EBC) is a potential sample for follow up of drug concentrations. Methods: A dispersive liquid-liquid microextraction (DLLME) procedure followed by a validated liquid chromatography method was employed for the determination of budesonide (BDS) in EBC samples collected using a homemade setup. EBC is a non-invasive biological sample with possible applications for monitoring drug concentrations. The proposed analytical method is validated according to the FDA guidelines using EBC-spiked samples. Its applicability is tested on EBC samples collected from healthy volunteers receiving a single puff of BDS. Results: The best DLLME conditions involved the use of methanol (1 mL) as a disperser solvent, chloroform (200 μL) as an extraction solvent, and centrifugation rate of 3500 rpm for 5 minutes. The method was validated over a concentration range of 21-210 μg·L-1 in EBC. Inter- and intra-day precisions were less than 10% where the acceptable levels are less than 20%. The validated method was successfully applied for the determination of BDS in EBC samples. Conclusion: The findings of this study indicate that the developed method can be used for the extraction and quantification of BDS in EBC samples using a low cost method.

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