Anatoly B. Volynsky
Russian Academy of Sciences
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Featured researches published by Anatoly B. Volynsky.
Spectrochimica Acta Part B: Atomic Spectroscopy | 2000
Anatoly B. Volynsky
Abstract Data on mechanisms of action of chemical modifiers based on Pd, Pt, Rh, Ru and Ir in electrothermal atomic absorption spectrometry (ETAAS) are critically discussed. In a very simplified form, the sequence of processes affording thermal stabilization of analytes by platinum group metal (PGM) modifiers appears to be the following: low-temperature stabilization of volatile analyte species is reached as a result of their chemisorption on the surface of the modifiers and/or on the graphite surface. At higher temperatures reached in the pyrolysis stage, reduction by the graphite (or thermal dissociation) of analyte species catalyzed by PGM modifiers occurs. The elemental analytes so formed interact with elemental PGM modifiers via formation of the corresponding solid solutions and/or stoichiometric compounds. According to existing knowledge, under correctly optimized conditions, analyte–PGM modifier compounds decompose completely during the atomization stage. Consequently, from the viewpoint of minimization of analyte losses, the processes of formation of these compounds during the pyrolysis stage are most critical. Existing theories can not explain the significant differences in the efficiency of Pd, Pt, Rh, Ru and Ir when used as modifiers in ETAAS.
Spectrochimica Acta Part B: Atomic Spectroscopy | 1998
Anatoly B. Volynsky
Abstract Data relating to practical applications of carbide-modified graphite atomizers (CMGAs) published mainly since 1985 are critically discussed. All elements being determined by means of electrothermal atomic absorption spectrometry are divided into ten groups according to their characteristics in graphite atomizers. CMGAs are the most effective for the determination of the elements forming rather stable oxides, such as Ge, Sn, Ga, In, as well as B and Si. The application of CMGAs to the determination of carbide-forming elements (Cr, Mo, V, Ti, etc.) may cause a significant decrease in their sensitivity. Concerning the high-volatility analytes (semi-metals and boron), CMGAs are usually effective only in the presence of regular chemical modifiers, primarily the salts of Pd and Ni. CMGAs may be successfully used for the determination of some organoelement (with Sn, Pb, Se, As) compounds, as well as for the trapping of volatile hydrides. CMGAs seem to be especially promising for analysis of biological samples, organic extracts, solid samples and samples containing high concentrations of mineral acids. High-melting carbides are prospective permanent modifiers.
Spectrochimica Acta Part B: Atomic Spectroscopy | 1998
Anatoly B. Volynsky
The principal processes taking place in graphite tubes modified with high-melting carbides are critically discussed. Analysis of the published data supports the idea that these processes depend largely on the tube treatment procedure applied and on the properties of the corresponding carbide. Therefore, the most commonly used methods of tube treatment and some properties of high-melting carbides are described. Depending on the composition and structure of the carbide layer, the reactivity of graphite may increase or decrease. For both situations, the reasons for changes in the sensitivity and lifetime of the graphite tube are discussed. The major processes taking place in carbide-modified graphite tubes seem to be of a catalytic nature. For further research, a wider application of ideas and methods from other fields of science seems to be most promising.
Spectrochimica Acta Part B: Atomic Spectroscopy | 1996
Anatoly B. Volynsky
The chemical processes in graphite furnaces used for electrothermal atomic absorption spectrometry (ETAAS) are discussed from the viewpoint of catalysis. The main attention is given to consideration of the processes which occur in the presence of platinum metal compounds and transition metal carbides. It is shown that both these groups of chemical modifiers accelerate either the processes of reduction of inorganic compounds or the thermal destruction of organoelement compounds and volatile hydrides in the graphite furnace. It is assumed that the similarities in the action of platinum metal compounds and transition metal carbides are based on the resemblance of their catalytic properties. The approach proposed may be used both for the improvement of already known chemical modifiers and for the creation of new ones. In general, adoption of the methods and concepts widely applied in catalysis for fundamental investigations of processes in graphite furnaces appears to be rather useful.
Talanta | 2006
Anu Viitak; Anatoly B. Volynsky
Electrothermal atomic absorption spectrometry was used for the determination of Cd, Pb, As and Se in the whole blood, serum, hair reference standard materials and the samples of algae collected at the coastal Estonian regions of Baltik sea. Instead of tedious and time-consuming experimental comparison of various chemical modifiers, theoretical consideration of the problem was applied for choosing the most prospective one (colloidal Pd) for solution of the given task. The experimental data obtained proved correctness of the choice. Pure standard solutions in diluted nitric acid were used for construction of the calibration graphs. The same experimental conditions were applied for each analyte for calibration solutions and all samples studied. In spite of very limited optimization procedures used, all the values obtained agree well with the corresponding reference values. Accuracy of the analysis of the algae samples was checked by recoveries of the spikes that were in the region 91-109%. Detection limits reached are 0.021, 1.2, 0.62 and 1.1ngml(-1) for Cd, Pb, As and Se, respectively, in digests of biological samples.
Spectrochimica Acta Part B: Atomic Spectroscopy | 1996
Anatoly B. Volynsky; Viliam Krivan; Sergei V. Tikhomirov
Abstract The effect of palladium, platinum, rhodium and iridium on the behaviour of selenium in the graphite furnace for electrothermal atomic absorption spectrometry (ETAAS) has been investigated by the radiotracer technique. These chemical modifiers have been used both in the chloride and in a reduced form, the latter being achieved by preliminary pyrolysis at 1000°C. The losses of selenium were observed during the pyrolysis stage for every modifier studied. For prereduced Pd, Pt, Rh and Ir as chemical modifiers, at the pyrolysis temperature of 600°C these losses amount up to 13%, 32%, 41% and 65%, respectively. In most instances, the effectiveness of chlorides of the platinum metals is lower than that of the pre-reduced modifiers. It is postulated that the dissolution of elemental selenium in palladium and platinum at relatively low temperatures diminishes losses of selenium in the pyrolysis stage.
Spectrochimica Acta Part B: Atomic Spectroscopy | 1998
Anatoly B. Volynsky
Modern trends in the research of the action of chemical modifiers for electrothermal atomic absorption spectrometry (ETAAS) are discussed critically. The most prolific approach is that of investigation of processes occurring during the drying and pyrolysis stages with wide application of data from different fields of chemistry and physics.
Spectrochimica Acta Part B: Atomic Spectroscopy | 2002
Anatoly B. Volynsky; Rainer Wennrich
Abstract The characteristics of As, Se and In in pure solutions in the presence of pre-reduced Pd, Rh, Ru, Pt and Ir modifiers in the transverse heated graphite atomizer (THGA) for electrothermal atomic absorption spectrometry are studied. Main attention is given to the influence of a wide range of modifier masses to sensitivity and shape of the absorption signals. Over-stabilization of As and In was observed in the presence of moderate amounts of the Pt modifier. Over-stabilization of As begins in the presence of approximately 2 μg of Rh and the addition of 25 μg of this modifier result in almost 3-fold suppression in the integrated absorbance. More than 2-fold suppression was also observed for the In absorption signals in the presence of 25 μg of Ru modifier. Modern knowledge of mechanisms on the action of platinum metal modifiers can neither predict, nor explain these element-specific interactions. Clear correlation between physical properties of the modifiers and analytes, and the data obtained could not be recognized as well. This significant contribution to chemical processes to stabilization of analytes during pyrolysis stage and their subsequent atomization. Some modern approaches concerning mechanisms of the action of platinum group metal modifiers are critically discussed and some trends are underlined.
Journal of Analytical Atomic Spectrometry | 1997
Anatoly B. Volynsky; Viliam Krivan
The effect of Pd, Pt, Rh, Ru and Ir on the behaviour of selenium in a transversely heated graphite atomizer for ETAAS was investigated. The chemical modifiers were used mainly in a thermally pre-reduced form. For all modifiers studied, the maximum pyrolysis and optimum atomization temperatures for selenium were approximately the same (about 1200 and 1600–1800 °C, respectively). There does not appear to be any correlation between these parameters and the melting-points of the modifiers used. Under optimized conditions, losses of about 10% of selenium at pyrolysis temperatures of 400–800 °C were observed for the pre-reduced Rh and Ru modifiers. The characteristic mass for selenium in the presence of pre-reduced Pt metal modifiers varied from 27.5 pg with the Pd modifier in a new graphite tube to 38.6 pg with the Pt modifier in a ‘used’ tube. All pre-reduced platinum group metals studied enabled the negative influence of up to 500 µg of chloride ion (as NaCl) on the determination of selenium to be eliminated. The efficiency of modification of chlorides of the platinum metals studied is very low, except for RhCl 3 . In general, they can even act as an additional source of interference.
Spectrochimica Acta Part B: Atomic Spectroscopy | 2001
Anatoly B. Volynsky; Alexandr Yu. Stakheev; Natalia S. Telegina; Valery G. Senin; L. M. Kustov; Rainer Wennrich
Abstract The low-temperature interaction (up to 550°C) of a pre-reduced palladium modifier with sodium sulfate and sodium selenite on the pyrolytic graphite platform was studied using X-ray photoelectron spectroscopy (XPS) and electron microprobe analysis. The equipment applied allowed the introduction of samples heated in an argon flow into the analytical chamber of the XPS spectrometer without contact with the air. Electron microprobe analysis showed that palladium and sulfur preferably occupy different areas on the platform surface. On the contrary, selenium from sodium selenite tends to occupy areas of the graphite surface covered with palladium. The most probable reason for this is the chemisorption of selenium (IV) on the palladium surface at the drying stage. No changes in the XPS spectra of metallic Pd and S6+ were observed when Na2SO4 and Pd were heated together on the graphite platform in the range 100–550°C. The reduction of sodium selenite on the graphite surface already starts during drying. Pre-reduced palladium intensifies this process. The rate of the reduction is proportional to the amount of palladium, and in the presence of palladium at an atomic ratio of Pd/Se=7.5, the transformation of Se4+ into Se0 completes at 250°C.