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1
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Voltammetric behavior and quantitative determination of ambazone concentrations in urine and in a pharmaceutical formulation

100%
Smarzewska S., Guziejewski D., Skowron M., Skrzypek S., Ciesielski W.
Open Chemistry
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2014
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vol. 12
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issue 12
1239-1245
EN
The use of square wave adsorptive stripping voltammetry (SWAdSV) in conjunction with a cyclic renewable silver amalgam film electrode (Hg(Ag)FE) for the analytical determination of ambazone in urine samples and pharmaceutical formulations is described. A single reduction peak in Britton-Robinson buffer at pH 4.0 was detected at about −1.4 V versus Ag/AgCl. Mechanistic studies have shown that the compound can act as an electrocatalyst. The method was validated. The analytical curve was linear in the concentration range from 1.0×10−9 to 1.0×10−7 mol L−1. The detection and quantification limits were found to be 3.0×10−10 mol L−1 and 1.0×10−9 mol L−1, respectively. The proposed method was successfully applied to ambazone determination in real samples.
2
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Differentiation between phenol- and amino-substances in voltammetry determination of synthetic antioxidants in oils

100%
Chýlková J., Šelešovská R., Machalíková J., Dušek L.
Open Chemistry
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2010
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vol. 8
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issue 3
607-616
EN
The paper describes a method of voltammetric determination of antioxidants in lubricating oils developed with the use of Linear Sweep Voltammetry (LSV) and Fast Scan Differential Pulse Voltammetry (FSDPV). Experimental conditions have been found for simultaneous determination of phenol-based antioxidants and amino-antioxidants: the phenols can be electrochemically oxidized using the polarisation of gold disc electrode (AuDE) in the potential range of 0–1400 mV in 0.2 M H2SO4 in the presence of ethanol and acetonitrile at the ratio of 3:1. Secondary aromatic amines can be determined directly in this supporting electrolyte; the presence of phenolic antioxidants does not interfere with this analysis. On the other hand, secondary aromatic amines interfere with the determination of phenolic substances; therefore, the amines present have to be eliminated in a suitable way. A procedure for masking the aromatic amines using their reaction with nitrous acid has been suggested and optimised. The nitrosamines thus formed can be used for sensitive and selective determination of amino-antioxidants by means of cathodic reduction on the hanging mercury drop electrode (HMDE) using Fast Scan Differential Pulse Voltammetry. The method was applied in analysis of real samples of lubricating oils. [...]
3
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Electrochemical oxidation of methylthiomethyleneisoquinolinium chloride - the first water soluble alkylthiomethylene substituted ammonium salt

100%
Smarzewska S., Skrzypek S., Bachowska B., Bałczewski P., Ciesielski W.
Open Chemistry
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2011
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vol. 9
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issue 5
840-845
EN
Electrochemical oxidation of methylthiomethyleneisoquinolinium chloride (MTMIQ), the first alkylthiomethyl substituted ammonium salt, which is fully miscible with water has been investigated by voltammetric (SWV) method using glassy carbon electrode. On the electrode, MTMIQ undergoes oxidation at the potential near Ep = 0.07V (vs. Ag/AgCl/3 M KCl). The influence of the pH of buffers, amplitude, frequency, step potential on the received signal was studied. The best results were obtained with a citrate buffer at a pH of 5. The oxidation peak current used for MTMIQ voltammetric determination was in the range of 2–8×10−5 mol L−1, LOD = 3.7×10−6, LOQ = 1.2×10−5. The product of the oxidation was accumulated at the working electrode and was investigated by spectroscopic method. Mechanistic pathways of the oxidation have been proposed. [...]
4
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Differential pulse voltammetry in analysis of disinfectants - 2-mercaptobenzothiazole, 4-chloro-3-methylphenol, triclosan, chloramine-T

100%
Baranowska I., Bijak K.
Open Chemistry
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2010
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vol. 8
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issue 6
1266-1272
EN
The aim of this work was to study the possibility of simultaneous voltammetric determination of some disinfectants used as components in cosmetic products. The examined compounds were: triclosan (5-chloro-2-(2,4-dichlorophenoxy)phenol), chloramine-T (N-chloro-p-toluenesulfonamide sodium salt), 4-chloro-3-methylphenol and 2-mercaptobenzothiazole. Measurements were performed using glassy carbon electrode immersed in Britton-Robinson buffers which acted as supporting electrolytes. The dependence of oxidation and reduction potentials on pH was examined using cyclic voltammetry. Britton-Robinson buffer of pH 9.9 was chosen for further studies to ensure the best separation of compounds. The resultant oxidation potentials indicate the possibility to simultaneously determine some of the disinfectants.. Oxidation reactions of mixtures containing two compounds (4-chloro-3-methylphenol and chloramine-T, 2-mercaptobenzothiazole and 4-chloro-3-methylphenol, 2-mercaptobenzothiazole and triclosan) were recorded as differential pulse voltammograms.
5
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Voltammetric methods of reboxetine analysis and the mechanism of its electrode reactions

100%
Altunöz-Erdoğan D., Erk N., Kılıç E.
Open Chemistry
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2013
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vol. 11
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issue 5
706-716
EN
Reboxetine (RBX) electrochemical redox behavior at hanging mercury drop (HMDE) and glassy carbon electrodes (GCE) was studied in various pH Britton-Robinson universal buffers using cyclic voltammetry and square-wave voltammetry. RBX was reduced at the HMDE and oxidized at the GCE with reversible adsorption controlled and irreversible diffusion controlled processes respectively. The anodic peak is due to the amine and the cathodic peak may correspond to oxygen protonation. An oxidation reaction mechanism is proposed. The linear relation between peak currents and RBX concentration allowed simple, sensitive, precise and inexpensive voltammetric procedures to be developed. The limit of detection was 0.04 µM RBX. The procedures were successfully applied to human urine and RBX tablet assay. Therapeutic RBX concentrations in human serum were not detected due to strong drug-protein binding. Using bovine serum albumin, the methods were used to investigate the effect of serum protein binding on RBX determination. [...]
6
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Voltammetric determination of Rutin at Screen-Printed carbon disposable electrodes

88%
Oliveira-Roberth A., Santos D., Cordeiro D., Lino F., Bara M., Gil E.
Open Chemistry
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2012
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vol. 10
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issue 5
1609-1616
EN
Rutin is a flavonoid commonly employed for many therapeutic purposes. Although the electroactive phenolic groups of rutin might be oxidized at low applied potential, the adsorption of oxidized species changes the electrode surface. As a consequence, the repeatability and reproducibility of the method decreases, which limits electroanalytical applications. This paper describes the use of disposable screen-printed electrodes as an alternative to improve the electrochemical quantification of rutin in commercial and standard samples. The electrochemical behavior was consistent to what is observed using other carbon electrodes: an adsorption-involved step and a pH-dependent oxidation process. The replacement of the electrodes between the analyses ensured rapid analysis, good intermediate precision and repeatability. The proposed method was successfully applied to rutin determination in pharmaceutical samples of capsules, with the limit of quantification being 0.30 µM. [...]
7
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Voltammetric method for ultra-trace determination of total mercury and toxic metals in vegetables. Comparison with spectroscopy

88%
Locatelli C., Melucci D.
Open Chemistry
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2013
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vol. 11
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issue 5
790-800
EN
A new procedure for the determination of mercury(II), copper(II), lead(II), cadmium(II) and zinc(II) traces in food matrices by square wave anodic stripping voltammetry and standard addition method is proposed. A rapid, inexpensive and multi-analyte analytical method suitable for food safety control is provided. Comestible vegetables were chosen as samples. A two-step, sequential determination was defined, employing two working electrodes: a gold electrode (GE) for mercury(II) and copper(II), and subsequently a hanging mercury drop electrode (HMDE) for copper(II), lead(II), cadmium(II) and zinc(II). No sample pre-treatment was needed. Spinach leaves, tomato leaves and apple leaves were employed as standard reference materials to optimize and defined the analytical procedure. The new method shows good selectivity, sensitivity, detectability and accuracy. A critical comparison with spectroscopic measurements is discussed. Spinach, lettuce and tomato samples sold on the market were analysed as real samples. Lead(II) and cadmium(II) concentration exceeded the relevant legal limits. [...]
8
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A study of the antioxidative behavior of phenolic acids, in aqueous herb extracts, using a dsDNA biosensor

88%
Skeva E., Girousi S.
Open Chemistry
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2012
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vol. 10
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issue 4
1280-1289
EN
Electrochemical DNA biosensors are promising tools for the fast, inexpensive and simple in vitro analysis for the determination of free radicals and antioxidants. High concentrations of antioxidants in such compounds as phenolic acids and plant extracts, act as free radical terminators which reduce the effect of the oxidative dam-age on DNA. The electrochemical behavior of three representative phenolic acids, caffeic acid, gallic acid and trolox were studied by cyclic voltammetry. Moreover, the determination of the above antioxidants under the optimized conditions (scan rate, deposition potential and time) using differential pulse voltammetry was also investigated. In vitro studies focused on their antioxidative effect were performed by adsorptive transfer stripping voltammetry and dsDNA biosensor. Using Fenton’s system, with FeSO4 and H2O2 was chosen as a strong oxidative system. This biosensor was applied as a screening antioxidant test in order to estimate the antioxidant capacity of aqueous herb extracts. [...]
9
Content available remote

Optimization of analytical procedures for the simultaneous voltammetric determination of total Hg(II) in presence of Cu(II) in environmental matrices

88%
Melucci D., Montalbani S., Locatelli C.
Open Chemistry
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2012
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vol. 10
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issue 1
267-276
EN
The present work reports the critical comparison about the employment of three different supporting electrolytes (0.1 mol L−1 HClO4, 0.01 mol L−1 EDTA-Na2 + 0.06 mol L−1 NaCl + 2.0 mol L−1 HClO4 and 0.1 mol L−1 KSCN + 0.001 mol L−1 HClO4) and their instrumental and chemical optimisation for the simultaneous voltammetric determination of total mercury(II) and copper(II) in sediments and sea water at gold electrode, especially discussing the reciprocal interference problems. The differential pulse anodic stripping voltammetric (DPASV) measurements were carried out using a conventional three-electrode cell: a gold electrode (GE) as working electrode, a platinum wire and an Ag‖AgCl‖KClsat as auxiliary and reference electrodes, respectively. The analytical procedure was verified by the analysis of standard reference materials: Estuarine Sediment BCR-CRM 277, River Sediment BCR-CRM 320 and Mercury in Water NIST-SRM 1641d. Once set up on the standard reference materials, the analytical procedure was transferred and applied to sediments and sea waters sampled in a lagoon ecosystem connected with Adriatic Sea (Ravenna area, Italy).
10
Content available remote

Electrochemical determination of tyrosine in the presence of uric acid at a carbon paste electrode modified with multi-walled carbon nanotubes enhanced by sodium dodecyl sulfate

88%
Ghoreishi S., Behpour M., Delshad M., Khoobi A.
Open Chemistry
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2012
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vol. 10
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issue 6
1824-1829
EN
Tyrosine (Tyr) was quantitated with high sensitivity and selectivity in the presence of uric acid (UA) using a carbon paste electrode modified with multi-walled carbon nanotubes. Tyr and UA were catalytically oxidized with diffusion-controlled characteristics. They were determined simultaneously by differential pulse voltammetry with a potential difference of 350 mV. The electrocatalytic currents increase linearly with Tyr and UA concentrations 4×10−7−1×10−4 M and 3×10−7−2×10−4 M. Their detection limits were 1×10−7 and 5.1×10−8 M respectively. In the presence of sodium dodecyl sulfate the Tyr detection limit improved from 1×10−7 to 6.9×10−8 M. The electrode was successfully used to quantitate Tyr and UA in serum. [...]
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