scholarly journals USING AN ACTIVATED COPPER MICROELECTRODE FOR VOLTAMMETRIC DETERMINATION OF ALCOHOLS

2018 ◽  
Vol 13 (1) ◽  
pp. 22-32
Author(s):  
L. Yu. Martynov ◽  
T. V. Sitnikova ◽  
M. A. Lazov ◽  
I. Yu. Lovchinovsky ◽  
N. K. Zaitsev
Keyword(s):  
Photoelectron Spectroscopy ◽  
Analytical Signal ◽  
Copper Surface ◽  
Potential Range ◽  
Current Response ◽  
Optimal Conditions ◽  
Original Design ◽  
Factors Affecting ◽  
Naoh Solution

A method for fabricating a copper microdisk electrode of an original design based on 50 μm diameter wire sealed in borosilicate glass is described. The electrochemical properties of the copper microelectrode were studied by the method of steady-state voltammetry in a 2 M NaOH solution in the potential range from -1.1 to 0.8 V (versus saturated Ag/AgCl-electrode). In order to improve the electrochemical response a method for two-stage electrode activation based on a copper dissolution / redeposition procedure followed by polarization in an alkaline medium is suggested. Morphological and physico-chemical changes on copper surface after activation were examined by atomic force microscopy and X-ray photoelectron spectroscopy. After this procedure, the electrode showed a heterogeneous morphology with coarse texture and high roughness parameters, and a layer of catalytically active Cu(III) species was formed on copper surface. The best results were achieved with an activation time of 60 s and a polarization potential of -0.3 V. The effectiveness of the activation procedure was tested during the chronoamperometric determination of methanol, ethanol and ethylene glycol. Factors affecting the formation of the analytical signal of alcohols were studied, and optimal conditions of amperometric measurements were selected on their basis. Under optimal conditions, the metrological characteristics of the method were determined. The peak current response increases linearly with alcohols concentration over the range 0.01 - 0.45 M (0.04 - 3% v/v). The repeatability of the electrode response was evaluated as 3.8% (n = 10). The activated copper microelectrode was used for the determination of ethanol in pharmaceutical and other products.

A Two-step Electrodeposition of Pd-Cu/Cu2O Nanocomposite on FTO Substrate for Non-enzymatic Hydrogen Peroxide Sensor

2021 ◽  
Vol 17 ◽  
Author(s):  
Ke Huan ◽  
Li Tang ◽  
Dongmei Deng ◽  
Huan Wang ◽  
Xiaojing Si ◽  
...  
Keyword(s):  
Hydrogen Peroxide ◽  
Cyclic Voltammetry ◽  
Photoelectron Spectroscopy ◽  
Chemical Structure ◽  
Pd Nanoparticles ◽  
Optimal Conditions ◽  
Potential Oscillation ◽  
X Ray Diffraction ◽  
X Ray

Background: Hydrogen peroxide (H2O2) is a common reagent in the production and living, but excessive H2O2 may enhance the danger to the human body. Consequently, it is very important to develop economical, fast and accurate techniques for detecting H2O2. Methods: A simple two-step electrodeposition process was applied to synthesize Pd-Cu/Cu2O nanocomposite for non-enzymatic H2O2 sensor. Cu/Cu2O nanomaterial was firstly electrodeposited on FTO by potential oscillation technique, and then Pd nanoparticles were electrodeposited on Cu/Cu2O nanomaterial by cyclic voltammetry. The chemical structure, component, and morphology of the synthesized Pd-Cu/Cu2O nanocomposite were characterized by X-ray diffraction, scanning electron microscopy and X-ray photoelectron spectroscopy. The electrochemical properties of Pd-Cu/Cu2O nanocomposite were studied by cyclic voltammetry and amperometry. Results: Under optimal conditions, the as-fabricated sensor displayed a broad linear range (5-4000 µM) and low detection limit (1.8 µM) for the determination of H2O2. The proposed sensor showed good selectivity and reproducibility. Meanwhile, the proposed sensor has been successfully applied to detect H2O2 in milk. Conclusion: The Pd-Cu/Cu2O/FTO biosensor exhibits excellent electrochemical activity for H2O2 reduction, which has great potential application in the field of food safety.

scholarly journals APPLICATION OF MATHEMATICAL PLANNING OF THE EXPERIMENT IN THE CHOOSING THE OPTIMUM CONDITIONS OF THE VAPOR-PHASE GAS-CHROMATOGRAPHIC DETERMINATION OF FORMALDEHYDE IN THE URINE

2018 ◽  
Vol 97 (10) ◽  
pp. 985-989 ◽  
Author(s):  
Аnton N. Alekseenko ◽  
O. M. Zhurba
Keyword(s):  
Mathematical Model ◽  
Vapor Phase ◽  
Statistical Processing ◽  
Analytical Signal ◽  
Heating Time ◽  
Gas Extraction ◽  
Optimal Conditions ◽  
Steep Ascent ◽  
The Mathematical Model

Introduction. There was substantiated a method for the determination of formaldehyde by vapor-phase gas chromatography by the use of derivatizing reagent o-(2,3,4,5,6-pentafluorbenzyl)hydroxylamine. Material and methods. Formaldehyde in urine was derivatized to o-pentafluorobenzyloxime and recovered to the vapor phase by heating the urine sample with o-(2,3,4,5,6-pentafluorbenzyl)hydroxylamine in a sealed vial. Gas-chromatographic analysis of the vapor-air phase was performed in a mode of the temperature gradient on a capillary column HP-5 with a flame ionization detector. Identification of the analyte in the form of the derivative-o- pentafluorobenzyloxime of formaldehyde was carried out according to the absolute retention time, which was established by comparing the chromatograms of model formaldehyde mixtures in the urine of different concentrations. Results. The optimal conditions for gas extraction are selected using mathematical experimental planning. The most important factors of gas extraction in the vapor-phase analysis are the temperature and time of the establishment of the interphase equilibrium with heating. From the experimentally obtained curves of the analytical signal on the temperature and the heating time, the zero level and the interval of variation of these factors are chosen. A matrix for planning a 2-factor experiment was constructed. The coefficients of the mathematical model are determined. There was carried out statistical processing of the experimental data, which was reduced to the estimation of the reproducibility of the optimization parameter and to the evaluation of the significance of the coefficient of the mathematical model. The adequacy of the mathematical model was evaluated, its interpretation was carried out. Discussion. The peak area of the analyte increases with the elevating the temperature and heating time, due to an increase in the analyte concentration in the vapor phase. Moreover, the heating time makes a greater contribution to the formation of the analytical signal than the temperature. The step of motion along the gradient was calculated and the experiments of steep ascent were carried out. Conclusion. According to the results of the steep ascent experiments, the optimal conditions for the gas extraction of formaldehyde in the form of a derivative were chosen.

scholarly journals SPECTROPHOTOMETRIC DETERMINATION OF ANTIOXIDANT SODIUM METABISULPHITE CONTENT IN PREPARED MEDICINAL FORMS OF VETERINARY MEDICINAL PRODUCTS

2020 ◽  
Vol 21 (2) ◽  
pp. 189-198
Author(s):  
H. Yu. Teslyar ◽  
M. Ya. Smolinska ◽  
I. Ya. Kotsyumbas ◽  
N. M. Chyhyn ◽  
N. G. Rohulia ◽  
...  
Keyword(s):  
Spectrophotometric Determination ◽  
Storage Time ◽  
Analytical Signal ◽  
Veterinary Drugs ◽  
Biologically Active Substances ◽  
Biologically Active ◽  
Optimal Conditions ◽  
Sodium Metabisulphite ◽  
Active Substances

An analytical method for the quantitative determination of antioxidant sodium metabisulphite in veterinary drugs has been proposed by spectrophotometric method. Based on the literature data, the optimal conditions of the analytical reaction were selected experimentally. The dependence of the value of the analytical signal on the temperature of the reaction medium, concentration of p-rosaniline and duration of the reaction was investigated to establish the optimal conditions of the analytical reaction and obtain a stable analytical signal. The stability of the colored analytical form in time was also checked and the linear dependence of the value of the analytical signal on the concentration of sodium metabisulphite was investigated. The analytical reaction at room temperature is optimal. The maximum analaytical signal is achieved by carrying out the analytical reaction for 10 minutes and then practically does not change for an hour. To achieve the maximum analytical signal, it is necessary to use a 20-fold excess of dye relative to sodium metabisulphite. The analytical signal remains stable only for the first hour, then gradually begins to decrease. Metrological characteristics of the method of determination of metabisulphite in veterinary drugs are calculated, the limits of spectrophotometric determination are 0.33 – 2.50 μg/ml. The correctness of the developed method was checked on model solutions by the method of "introduced-found" method of comparison in the presence of various biologically active substances that are part of drugs together with sodium metabisulphite. The content of sodium metabisulphite in veterinary drugs of domestic and foreign production at different intervals of their storage time was established. It is shown that the content of sodium metabisulphite in drugs decreases during their storage time, until complete disappearance, which directly affects the content of the active substance, because in the absence of antioxidant oxidative processes with biologically active substances begin to take place.

Optimization of the spectrophotometric determination of mercury using copper(II) diethanoldithiocarbamate

1985 ◽  
Vol 50 (8) ◽  
pp. 1661-1672 ◽  
Author(s):  
Ernest Beinrohr ◽  
Katarina Blazseková ◽  
Ján Garaj
Keyword(s):  
Spectrophotometric Determination ◽  
Absorption Maximum ◽  
Ph Value ◽  
Rapid Determination ◽  
Analytical Signal ◽  
Aqueous Acetone ◽  
Determination Limit ◽  
Factors Affecting ◽  
Analytical Calibration

The work deals with the optimization of the conditions for the spectrophotometric determination of mercury using copper(II) diethanoldithiocarbamate [Cu((HOCH2CH2)2NCS2)2] (I). The determination is based on replacement of Cu2+ ions by Hg2+ ions in complex I in acidic aqueous acetone medium and measuring the decrease in the absorbance at the absorption maximum of complex I (λ = 440 nm). The statistical importance of the factors affecting the analytical signal (absorbance) was found by the analysis of variance. The analytical signal is affected most by the pH value, the concentration of Cu2+ ions, and the acetone content. The best results were obtained at pH ~ 2 and an acetone content of 15% (v/v). The analytical calibration curve is nonlinear. The determination limit is 50 μg Hg in 1 dm3. The method is useful for the rapid determination of mercury with a precision of ± 5% in colourless solutions not containing Cu2+ or Ag+ ions or strong oxidants.

Determination Of The Content Of Hf In Zirconium Alloys With Using A Wide Band X-Ray Emission Filter

2018 ◽  
pp. 153-159
Author(s):  
O.P. Omelnyk ◽  
V.V. Levenets ◽  
A.Yu. Lonin ◽  
I.V. Shevchenko ◽  
A.O. Shchur
Keyword(s):  
Pyrolytic Graphite ◽  
Zirconium Alloys ◽  
Analytical Signal ◽  
Wide Band ◽  
Optimal Conditions ◽  
Experimental Conditions ◽  
X Ray ◽  
Method Of Determination ◽  
Non Destructive

The possibilities of a non-destructive method of determination of the content of hafnium in zirconium alloys are studied. The method is based on excitation of the characteristic X-ray emission of the atoms of the object of interest, including the L-series of atom of Hf, by external beam of protons accelerated up to 2 MeV. The excited emission is modified by a wide band X-ray emission filter, which is made from pyrolytic graphite plates and measured by a Si-PIN detector. Optimal conditions for measurement of analytical signal were determined after experimental studying. It was shown that under the selected experimental conditions and the measurement time of 10 minutes, the detection limit of Hf in the zirconium matrix is equal 20 ppm. The ways for improving of the metrological characteristics of the technique in the presence of interfering elements are proposed. The content of hafnium and uniformity of its distribution in the cladding of nuclear fuel rod made from the alloy Zr1% Nb was determined.

SPECTROPHOTOMETRIC DETERMINATION OF HEAVY METALS IN SOILS

2019 ◽  
Vol 85 (5) ◽  
pp. 18-27
Author(s):  
K. A. Kuliev ◽  
N. A. Verdizadeh
Keyword(s):  
Ph Value ◽  
Analytical Signal ◽  
Optimal Conditions ◽  
Photometric Detection ◽  
River Floodplains ◽  
Highly Sensitive ◽  
Optimum Ph ◽  
Heavy Metals In Soils ◽  
Different Soils

Simple, selective and highly sensitive extraction-photometric methods for determination of Cu, Hg, У Mn, Fe, Co, and Ni are developed using dimercaptophenols (DF) and hydrophobic amines (Am) (2,6-dimercaptophenol(DMP), 2,6-dimercapto-4-methylphenol(DMMP), 2,6-dimercapto-4-ethylphenol(DMEP), 2,6-dimercapto-4-propylphenol(DMPP), and 2,6-dimercapto-4-tertbutylphenol(DMBP)) as complexing reagents. Optimal conditions for formation and extraction of heteroligand compounds (HLC) are specified and the ratios of the components in the complexes are determined. The optimum pH value providing maximum and constant optical density ranges within 3.0-8.1, chloroform (extraction ratio: 98.4-99.6%) being used as an extractant. Optimal concentrations of DP and Am are (0.6 - 0.8) x 10-3and (0.8 - 1.2) x 10-3mol/liter, respectively. HLC are stable and do not decompose for three days in aqueous and organic solvents, and after extraction for more than a month. The maximum analytical signal for M(II) complexing with DP and Am is observed at 464 - 630 nm (εk= 1.82 - 4.40 x 104). The structure of the HLC was studied using thermogravimetry and IR-spectroscopy Comparison of the analytical capabilities of the studied reagents showed that the contrast and sensitivity of the reaction decreases in the series DMBP — DMPP — DMEP — DMMP — DME The interfering impact of ions can be eliminated through changing pH of the medium, masking substances and extraction. The limits of photometric detection and quantitative determination of M (II) in the form of HLC were calculated using calibration graphs. The developed procedures have been successfully used in determination of the trace amounts of Cu, Hg, У Mn, Fe, Co, Ni in different soils: sod-podzolic sandy and sandy-loamy sod-podzolic loamy and clayey, gray forest, black soils, chestnut and river (soil of river floodplains) soils. The determination limits range within 27 - 43 ng/cm3.

The effect of thiazine dyes on polarographic determination of tellurium

1991 ◽  
Vol 56 (1) ◽  
pp. 216-222
Author(s):  
Ludmila Kiriyak
Keyword(s):  
Methylene Blue ◽  
Binary Mixtures ◽  
High Purity ◽  
Electrochemical Reaction ◽  
Analytical Signal ◽  
Electrode Process ◽  
Polarographic Determination ◽  
Optimal Conditions ◽  
Thiazine Dyes

The effect of thionine, azure I and methylene blue on the electroreduction of tellurium(IV) has been studied in the solutions of oxalic, tartaric and trihydroxyglutaric acids. It has been shown that the electrode process is complicated by adsorption of all components of the electrochemical reaction. This causes an increase of the tellurium analytical signal. The determinations is not hampered by great excesses of various elements. Optimal conditions were found according to which determinations were carried out of tellurium in binary mixtures Pb-Te, Cd-Te, Fe-Te, Bi-Te and of tellurium admixtures in bismuth of high purity, doped by tellurium.

Modeling of dynamic mosaicism on ring chromosomes in human fibroblasts and IPSCS

2020 ◽  
pp. 12-13
Author(s):  
Т.В. Никитина ◽  
А.А. Кашеварова ◽  
М.М. Гридина ◽  
А.А. Хабарова ◽  
А.Г. Мензоров ◽  
...  
Keyword(s):  
Genetic Structure ◽  
Human Fibroblasts ◽  
Cellular Heterogeneity ◽  
Mitotic Stability ◽  
Factors Affecting ◽  
Ring Chromosomes ◽  
Cell Clones ◽  
Mitotic Instability ◽  
Mitotic Behavior

Митотическая нестабильность кольцевых хромосом может приводить к появлению клеточных клонов с различной генетической структурой. В качестве модели нестабильности кольцевых хромосом в митозе мы использовали фибробласты от пациентов с r(8), r(13), r(18) и r(22) и полученные из них индуцированные плюрипотентные стволовые клетки (ИПСК). Линии ИПСК с r(22) имели относительно стабильный кариотип на протяжении десятков (до 60) пассажей и сохраняли неизменную структуру кольцевой хромосомы. Кариотип линий ИПСК с r(8) и r(18) на ранних пассажах стабильный, планируется его изучение на поздних пассажах. Наибольшее разнообразие кариотипа выявлено в линиях ИПСК с r(13), в которых наблюдали различные перестройки и выраженную клеточную гетерогенность. Определение факторов, влияющих на митотическую стабильность кольцевых хромосом, может иметь значение для консультирования пациентов. Mitotic instability of ring chromosomes can lead to the appearance of cell clones with different genetic structure. IPSCs from fibroblasts of patients with r(8), r(13), r(18), and r(22) were used as a model of ring chromosomes mitotic behavior. Karyotypes of iPSC lines with r(8) and r(18) have so far been evaluated only in the early passages, lines with r(22) have maintained a relatively stable karyotype up to 60 passages. The occurrence of rearrangements and cellular heterogeneity was found characteristic for r(13) iPSCs. The determination of factors affecting the ring chromosomes mitotic stability would be beneficial for the patient’s prognosis.

Dc arc emission analysis of rare earth metals and their oxides with sorption preconcentration of impurities

2018 ◽  
Vol 84 (11) ◽  
pp. 9-14
Author(s):  
E. S. Koshel ◽  
V. B. Baranovskaya ◽  
M. S. Doronina
Keyword(s):  
Rare Earth ◽  
Rare Earth Metals ◽  
Analytical Signal ◽  
Graphite Powder ◽  
Atomic Emission ◽  
Standard Samples ◽  
Emission Analysis ◽  
Sorption Preconcentration ◽  
Sample Shape

The analytical capabilities of arc atomic emission determination of As, Bi, Sb, Cu, Te in rare earth metals (REM) and their oxides after preparatory group concentration using S,N-containing heterochain polymer sorbent are studied on a high-resolution spectrometer “Grand- Extra” (“WMC-Optoelectron-ics” company, Russia). Sorption kinetics and dependence of the degree of the impurity extraction on the solution acidity are analyzed to specify conditions of sorption concentration. To optimize the procedure of arc atomic emission determination of As, Bi, Sb, Cu, and Te various schemes of their sorption preconcentration and subsequent processing of the resulted concentrate with the addition of a collector at different stages of the sorption process have been considered. Graphite powder is used as a collector in analysis of rare earth oxides due to universality and relative simplicity of the emission spectrum. Conditions of analysis and parameters of the spectrometer that affect the analytical signal (mass and composition of the sample, shape and size of the electrodes, current intensity and generator operation mode, interelectrode spacing, wavelengths of the analytical lines) are chosen. The evaporation curves of the determinable impurities were studied and the exposure time of As, Bi, Sb, Cu, and Te in the resulted sorption concentrate was determined. Correctness of the obtained results was evaluated using standard samples of the composition and in comparisons between methods. The results of the study are used to develop a method of arc chemical-atomic emission analysis of yttrium, gadolinium, neodymium, europium, scandium and their oxides in a concentration range of n x (10-2 - 10-5) wt.%.

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