A glassy carbon (GC) electrode was modified with cobalt pentacyanonitrosylferrate (CoPCNF) film. Cyclic voltammetry (CV) of the CoPCNF onto the GC (CoPCNF/GC) shows a redox couple (Fe
III/Fe
II) with ...a standard potential (
E
0′) of 580
mV. The current ratio
I
pa/
I
pc remains almost 1, and a peak separation (Δ
E
p) of 106
mV is observed in 0.5
M KNO
3 as the supporting electrolyte. Anodic peak currents were found to be linearly proportional to the scan rate between 10 and 200
mV
s
−1, indicating an adsorption-controlled process. The redox couple of the CoPCNF film presents an electrocatalytic response to sulfide in aqueous solution. The analytical curve was linear in the concentration range of 7.5
×
10
−5 to 7.7
×
10
−4
M with a detection limit of 4.6
×
10
−5
M for sulfide ions in 0.5
M KNO
3 solution.
We report the fabrication of a Ni nanoparticle modified BDD electrode and its application in the electrocatalysis of primary alcohol electrooxidation. Modification was achieved via electrodeposition ...from Ni(NO3)2 dissolved in sodium acetate solution (pH 5). Characterization of the Ni‐modified BDD (Ni‐BDD) was performed using ex situ atomic force microscopy (AFM) and high resolution scanning electron microscopy (SEM) coupled with energy dispersive X‐ray spectroscopy (EDX). Large nanoparticles of nickel were observed on the BDD surface ranging 5 to 690 nm in height and 0.18 μm−3 in volume, and an average number density of ca. 13×106 nanoparticles cm−2 was determined. The large range of sizes suggests progressive rather than instantaneous nucleation and growth. Electrocatalysis of ethanol and glycerol, was conducted in an alkaline medium using an unmodified BDD, Ni‐BDD and a bulk Ni macro electrode. The Ni‐BDD electrode gave the better electrocatalytic performance, with glycerol showing the greatest sensitivity. Linear calibration plots were obtained for the ethanol and glycerol additions over concentration ranges of 2.8–28.0 mM and 23–230 μM respectively. This gave an ethanol limit of detection of 1.7 mM and sensitivity of 0.31 mA/M, and the glycerol a limit of detection of 10.3 μM with a sensitivity of 35 mA/M.
A nickel modified boron doped diamond (Ni‐BDD) electrode and nickel foil electrode were used in the determination of methanol in alkaline solutions. The Ni‐BDD electrode was electrodeposited from a 1 ...mM Ni(NO3)2 solution (pH 5), followed by repeat cycling in KOH. Subsequent analysis utilised the Ni(OH)2/NiOOH redox couple to electrocatalyse the oxidation of methanol. Methanol was determined to limits of 0.3 mM with a sensitivity of 110 nA/mM at the Ni‐BDD electrode. The foil electrode was less sensitive achieving a limit of 1.6 mM and sensitivity of 27 nA/mM. SEM analysis of the electrodes found the Ni‐BDD to be modified by a quasi‐random microparticle array.
This work presents the analytical method development for iron and copper determination in ethanol fuel. This method was developed using stripping voltammetry with a glassy carbon electrode modified ...with Nafion/Carbon‐nanotubes. With linear sweep stripping voltammetry was achieved a limit of detection of 7.1×10−7 mol L−1 for Fe3+ and 5.1×10−8 mol L−1 for Cu2+. The amperometric sensitivities were 2.0×106 µA mol−1 L for Fe3+ and 2.8×107 µA mol−1 L for Cu2+. The recovery study showed that the method has good accuracy and repeatability, with recovery of 108 and 103 % for Fe3+ and Cu2+ respectively.
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•Reversed- phase chromatography was used to separate three antioxidants.•A rGO/AuNPs modified electrode was constructed and used as detector in HPLC-PAD.•The developed method is ...simple and requires short analysis time.•HPLC-PAD was used for the first time in the determination of antioxidants in biokerosene.•The developed detector led to the successful quantification of TBP and BHT in biokerosene.
This paper report the development of a new HPLC-pulsed amperometric detector (HPLC-PAD) for the determination of antioxidants using glass carbon electrode (GCE) modified with reduced graphene oxide (rGO) and gold nanoparticles (AuNPs). The modified electrode exhibited efficient electro-oxidation when it was applied in the analysis of three important antioxidants: N, N'-di-sec-butyl paraphenylenediamine (BPA), 2,6-Di-tert-butylphenol (TBP) and 2,6-Di-tert-butyl-4-methylphenol (BHT). The chromatographic separation was performed with an isocratic elution composed of acetonitrile/water (90:10% v/v) and 1% acetic acid. The chromatograms showed good separation of all components in periods of time less than 10 min. The developed method presented linear ranges of 5.0 × 10−6–1.3 × 10−4 mol L−1 (BPA), 2.5 × 10−6–1.0 × 10−4 mol L−1 (TBP) and 7.5 × 10−7–1.3 × 10−4 mol L−1 (BHT), and the analytical curves presented limits of detection of 1.2 × 10−7, 1.7 × 10−7 and 7.8 × 10−8 mol L−1 for BPA, TBP and BHT, respectively. The values obtained for the recovery studies conducted ranged from 97.3 ± 1.5% to 101.5 ± 2.1%. The results showed that the method is reliable, since it presented high sensitivity, precision and accuracy. The developed method was successfully applied for the determination of antioxidants in a sample of biokerosene, consisting of isoparaffins synthesized from fermented and hydroprocessed sugars. The determined concentrations were TBP 3.1 × 10−5 ± 5.5 × 10−6 mol L−1 and BHT 3.3 × 10−5 ± 2.9 × 10−6 mol L−1.
Solid paraffin-based carbon paste electrodes modified with 2-aminothiazole organofunctionalized silica have been applied to the anodic stripping determination of copper ions in ethanol fuel samples ...without any sample treatment. The proposed method comprised four steps: (1) copper ions preconcentration at open circuit potential directly in the ethanol fuel sample; (2) exchange of the solution and immediate cathodic reduction of the absorbate at controlled potential; (3) differential pulse anodic stripping voltammetry; (4) electrochemical surface regeneration by applying a positive potential in acid media. Factors affecting the preconcentration, reduction and stripping steps were investigated and the optimum conditions were employed to develop the analytical procedure. Using a preconcentration time of 20
min and reduction time of 120
s at −0.3
V versus Ag/AgCl
sat a linear range from 7.5
×
10
−8 to 2.5
×
10
−6
mol
L
−1 with detection limit of 3.1
×
10
−8
mol
L
−1 was obtained. Interference studies have shown a decrease in the interference effect according to the sequence: Ni
>
Zn
>
Cd
>
Pb
>
Fe. However, the interference effects of these ions have not forbidden the application of the proposed method. Recovery values between 98.8 and 102.3% were obtained for synthetic samples spiked with known amounts of Cu
2+ and interfering metallic ions. The developed electrode was successfully applied to the determination of Cu
2+ in commercial ethanol fuel samples. The results were compared to those obtained by flame atomic absorption spectroscopy by using the
F-test and
t-test. Neither
F-value nor
t-value have exceeded the critical values at 95% confidence level, confirming that there are no significant differences between the results obtained by both methods.
Potentiometric, amperometric and conductometric electrochemical sensors have found a number of interesting applications in the areas of environmental, industrial, and clinical analyses. This review ...presents a general overview of the three main types of electrochemical sensors, describing fundamental aspects, developments and their contribution to the area of analytical chemistry, relating relevant aspects of the development of electrochemical sensors in Brazil.
In this work the electrooxidations of glucose, galactose, mannose, rhamnose, xylose and arabinose are studied at a nickel hydroxide nanoparticle modified boron-doped diamond electrode and compared to ...an unmodified electrode. These carbohydrates are very important in the second-generation ethanol production process. Nickel hydroxide modified boron-doped diamond was characterized by scanning electron microscopy and energy dispersive X-ray. Electrochemical impedance spectroscopy was employed to study the interface properties of surface-modified electrodes in the absence and presence of the carbohydrates. Limits of detection were 5.3 × 10−5, 6.8 × 10−5, 2.7 × 10−4, 6.9 × 10−5, 8.8 × 10−5 and 2.6 × 10−5 mol L−1 for glucose, galactose, mannose, rhamnose, arabinose, xylose, respectively.
A mercury film electrode was used to determine direct and simultaneously Pb(II) (at −410mV) and Cu(II) (at −100mV) in biodiesel by anodic stripping voltammetry. A linear response was obtained for ...Pb(II) and Cu(II) in the 2.00×10−8–1.00×10−7molL−1 concentration range and detection limits were 2.91×10−9molL−1 and 4.69×10−9molL−1 for Pb(II) and Cu(II), respectively, with recovery around of 100.0%.
A cobalt film modified glassy carbon electrode was prepared by electrochemical deposition and its application was studied by potentiometry. The film modified electrode is used for the determination ...of phosphorus and exhibits a detection limit of 8.7×10−5molL−1 with recovery of 96.9%. This method has been used for determination of phosphorus ions in biodiesel samples with satisfactory results.
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