Separation of metal vapors for atomic spectroscopy techniques by high-temperature chromatography on graphite

Grinshteyn, Ilia L.; Копейкин, В. А.; Vasilieva, Lubov A; Golubev, S.N.; Kuss, Heinz Martin

doi:10.1016/s0584-8547(97)00033-5

Cited by 5 publications

(2 citation statements)

References 24 publications

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“…However, it follows from [23] that the diffusion coefficient for zinc is much higher than for copper and is commensurable with the coefficient of diffusion of silver in graphite. This conclusion qualitatively confirms our results.…”

Section: Introductionmentioning

confidence: 99%

Kinetic Model of Entry of Free Atoms into an Electrothermal Atomizer

et al. 2005

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A kinetic phenomenological model of the processes of atomization for atomic-absorptional spectrometry with electrothermal atomization that is based on solution of a one-dimensional equation of diffusion with two independent sources is suggested. The model takes into account the processes occurring both on the surface of a graphite furnace and inside its wall. The proposed model is used for describing the electrothermal atomization of copper and zinc.Introduction. It is known that in the method of atomic-absorption spectrometry with electrothermal atomization (ETAAS), a metered amount of the sample analyzed is delivered onto the graphite surface of a furnace (or platform) on which its thermal treatment and atomization occur. A liquid sample not only spreads over the surface but also penetrates into the pores of the furnace material under the action of capillary forces, as a result of which the conditions of sample atomization are altered [1,2]. It is evident that here the state and properties of the graphite surface play a significant role.It has been shown earlier [2-6] that the form of the analytical signal depends substantially on the state of the furnace surface and the degree of its wear, and the necessity of creating a model that would take into account penetration of a sample into the surface pores has been substantiated [2]. Such a model may also be of use in studying the influence of permanent modifiers on the mechanism of atomization [7].To construct a correct phenomenological model of sample atomization in a graphite furnace it is necessary to consider two sources of free atoms: one on the furnace surface and the other inside its walls. The present work is devoted to the solution of this problem. For experimental checking of the model, we selected copper and zinc, the mechanisms of atomization of which are different.Theory. In constructing the model, we use some facts and assumptions.1) The atomic absorption A(t) is proportional to the mass M(t) of the free atoms that are present in the analytical volume of the furnace in a gas phase.2) In delivering metered amounts of a sample into the furnace (or onto the platform), a portion of the liquid sample penetrates into graphite under the action of capillary forces [1, 2]. As the total initial mass of the atoms M 0 placed inside an atomizer we take the mass of the atoms participating in formation of an analytical signal. It can be represented as the sum of the masses of atoms on the surface of the furnace and inside its pores:

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Section: Introductionmentioning

confidence: 99%

Kinetic Model of Entry of Free Atoms into an Electrothermal Atomizer

et al. 2005

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“…Electrographite consists of two components: crystalline graphite, which is an allotropic form of carb- on having a layered structure and crystallizing in hexagonal syngony (σ electrons form a strong covalent bond in the planes, while π electrons form weak van der Waals bonds between planes), and also amorphous graphite filling the space between grains of crystalline graphite. The porosity of this material is 14%-20% [23]. Due to burn-off of the amorphous graphite, the porosity significantly increases and becomes more pronounced.…”

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Tungsten-assisted modification of graphite furnaces for an atomic absorption spectrometer

et al. 2009

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543.422We have used scanning electron microscopy to study changes in the morphology of the inner surface of graphite tube furnaces for an atomic absorption spectrometer when modified by tungsten. We have demonstrated the role of the tungsten-containing material as a dividing interlayer between the sample to be dispensed and the carbon component of the furnace. We consider the advantages and disadvantages of furnaces modified by the proposed methods.Introduction. The modifying properties of tungsten [1][2][3][4][5][6][7][8] are often used in atomic absorption spectrometers (AAS) with electrothermal atomization (ETA) [9,10] in order to enhance the analyte signal. Tungsten and its compounds also can be used as a permanent modifier to minimize the interaction between the analyte and the carbon component of the furnace. On the other hand, in analysis of shaping elements such as, for example, silicon [11,12], it is important to passivate this impurity in the carbon material that is complicated to remove. In order to create a barrier difficult to overcome for any sample component, including the analyte, usually a thin layer of the modifier on the surface of the furnace is sufficient.During a study of the parameters for silicon atomization signals from the surface of tungsten-modified graphite tube furnaces for ETA-AAS, considering the result of [13], we hypothesized that the effectiveness of the modification depends on the method used to treat the graphite furnaces with the modifier. Impregnating the furnace with sodium tungstate, other than improving the sensitivity of silicon determination, did not provide appreciable advantages over the standard furnace with a pyrolytic carbon coating. The positive effect of dispensing the sample with sodium tungstate was more pronounced for furnaces uncontaminated by silicon. Lining with tungsten foil improved the sensitivity and selectivity of the measurements, regardless of the presence of the analyte in the furnace material.The goal of this work was to use scanning electron microscopy to study the morphological features of the surface of graphite furnaces for different methods of tungsten-assisted modification.The Experiment. The studies were carried out on a RE ′ MMA-102 (SELMI, Ukraine) scanning electron microscope equipped with wavelength-dispersive and energy-dispersive x-ray spectrometers. The micrographs were obtained in secondary and backscattered electron detection modes with accelerating voltage 20 kV. A feature of backscatter microphotography is that the gray level is determined by the atomic number: the higher the atomic number of the material, the brighter the section of the image [14]. We used new graphite furnaces made by LEG (Kharkov) (average weight, ≈0.9 g [15]), analogous to a Perkin Elmer HGA-500 furnace (length 28 mm, inner and outer diameters 6 mm and 7.6 mm), for an A-5 atomizer (KAS-120.1 system [16]) made from MPG-6 graphite, and also old furnaces from the same manufacturer with average weight ≈0.8 g.The furnaces were modified by three methods [13]: by imp...

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Tungsten devices in analytical atomic spectrometry

Hou

Jones

2002

Spectrochimica Acta Part B: Atomic Spectroscopy

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Separation of metal vapors for atomic spectroscopy techniques by high-temperature chromatography on graphite

Cited by 5 publications

References 24 publications

Kinetic Model of Entry of Free Atoms into an Electrothermal Atomizer

Kinetic Model of Entry of Free Atoms into an Electrothermal Atomizer

Tungsten-assisted modification of graphite furnaces for an atomic absorption spectrometer

Tungsten devices in analytical atomic spectrometry

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