M. Yu. Burylin

Determination of lead and cadmium by atomic absorption spectrometry coupled with slurry sampling of carbonized samples : Use of palladium-bearing activated carbon as a matrix modifier

The determination of Pb and Cd by electrothermal atomic absorption spectroscopy with the slurry sampling of carbonized samples into a graphite furnace was considered. Textural and chemical properties of new palladium-carbon modifiers based on activated carbon and carbonized nutshell were studied by high-resolution electron microscopy, x-ray photoelectron spectroscopy, and the adsorption of liquid nitrogen. Advantages of activated carbon as a modifier support were substantiated. Pyrolysis and atomization temperatures were selected for determining elements using matrix modifiers. The developed analytical procedure was tested with reference samples of plant materials. The results obtained agreed well with the certified analyte concentrations. The RSD values were no higher than 8% for lead and cadmium in the ranges 0.3–3.3 and 0.110–1.34 mg/kg, respectively.

Permanent chemical modifiers in electrothermal atomic absorption spectroscopic analysis: A review

Publications on the use of permanent modifiers (PMs) in electrothermal atomic absorption spectroscopic analysis (ETAAS) were reviewed. Modifiers of thermally stable carbides (TCs), platinum group metals (PGMs), and their mixtures were characterized. The objects analyzed most frequently with the use of permanent modifiers were described in groups: organic solutions, suspensions and solid samples, materials after acid decomposition, and natural and drinking water. The results of the physicochemical studies of new sorbent modifiers and the thermodynamic and kinetic laws of thermochemical processes with their participation were presented.

Specific features of the determination of arsenic in soils by electrothermal atomic absorption spectrometry with the injection of suspensions

Problems of the determination of arsenic in soils by electrothermal atomic absorption with the injection of suspensions are discussed. To eliminate an exceptionally high rate of nonselective absorption due to intense evaporation of the inorganic matrix of the sample, the author proposed the reduction of the temperature to arsenic atomization. The optimized temperatures of pyrolysis and atomization steps are 500 and 1800°C, respectively; therein no matrix modifiers were used. The proposed approach was tested on reference samples of soils.

Development and properties of iron-containing chemical modifier based on activated carbon for electrothermal atomic absorption determination of volatile elements

The energies of chemisorption of As, Se, Pb, and Cd atoms by the metal surface of iron are calculated by the quantum chemistry method. The possibility of analytical application of an iron-containing chemical modifier (CM) on the basis of activated carbon for ETAAS determination of volatile elements is suggested. By the methods of thermodynamic modeling, thermal analysis, and ETAAS, the preparation procedure of iron-containing CM is justified on the basis of activated carbon, which ensures the formation of the metallic phase Fe0 and the course of low-temperature thermal stabilization of analytes. Using the developed chemical modifier, the contents of As, Cd, and Pb are determined in the suspensions of the standard sample of seaweeds. The results are in satisfactory agreement with the certified values.

Efficiency of a cobalt-containing matrix modifier based on activated carbon for the electrothermal atomic absorption determination of the highly volatile elements

The energies of the chemisorption of As, Se, Pb, and Cd atoms by palladium and cobalt metal surfaces were calculated by a quantum chemistry method. The analytical applicability of a cobalt-containing chemical modifier based on activated carbon to the determination of the highly volatile elements by electrothermal atomic absorption spectrometry (ETAAS) was hypothesized. A procedure for the preparation of the cobalt-containing chemical modifier based on activated carbon was substantiated using thermodynamic simulation, thermal analysis, and ETAAS. This procedure ensured the formation of a Co0 metal phase and the occurrence of thermal stabilizing interactions with analytes at the stage of drying. The concentrations of arsenic and lead in the suspensions of a standard reference sample of marine algae were determined with the use of the developed chemical modifier based on activated carbon. The experimental results were consistent with the certified values.

Determination of Arsenic by Electrothermal Atomic Absorption Spectrometry Using Arsine Preconcentration on Palladium-Containing Adsorbents

A procedure was developed for the preconcentration of arsine on palladium-containing adsorbents followed by the determination of arsenic by electrothermal atomic absorption spectrometry. Aqueous suspensions of the adsorbent were placed in a graphite furnace at the determination step. The selection of the adsorbent was substantiated; adsorption properties of palladium-containing adsorbents were studied to validate their modifying properties. The absolute and concentration limits of detection for arsenic were 28 pg and 12 ng/L, respectively (sample volume of 100 mL).

QUANTUM chemical estimation of the binding strength of As, Cd, Pb, Sb, Se, Te atoms by the ZrC(100) surface

The publication considers the modifying effect of refractory zirconium carbide in determining elements by hydride generation atomic absorption spectrometry. It is shown that the nature of binding of atoms of the analytes consists in the ability of the ZrC surface to strong adsorption. For As, Cd, Pb, Sb, Se, Te elements the adsorption energies of atoms on the ZrC(100) surface are calculated by the density functional theory. It is found that the necessary condition for adsorption is the preliminary cleaning of the ZrC surface from chemisorbed hydrogen. Correlation is demonstrated between the pyrolysis temperature that is maximum achievable for the analyte in the specimen with the adsorption energy of its atomic form on the ZrC(100) surface.

Development of electrothermal atomic absorption spectrometry in 2005–2016

The review covers publications of 2005–2016 on achievements in the development of electrothermal atomic absorption spectrometry (ETAAS). The main directions in the authors’ opinion are revealed, i.e., (1) improvements of the method and equipment and (2) studies of thermochemical processes in a graphite furnace. In the first group, the authors consider high- and low-resolution continuum source atomic absorption spectrometry, diode laser atomic absorption spectrometry, new designs of electrothermal atomizers, and new devices for ETAAS. Studies of mechanisms of element atomization, formation of analytical signals, and action of chemical modifiers belong to the second group.