A kinetic model for an atomic absorption signal

Rogul’skii, Yu. V.; Kholodov, R. I.; Sukhodub, L. F.

doi:10.1007/bf02757764

Cited by 5 publications

(10 citation statements)

References 12 publications

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“…As shown in [8], the time needed for establishing temperature equilibrium in the furnace is ,10 −5 sec, whereas the characteristic time of a change in the furnace surface temperature is 10 −3 sec. This relationship allows one to use the principle of adiabatic approximation, when at each time instant t the change in temperature is small, and it is possible to assume that the gas in the furnace is in thermodynamic equilibrium at the temperature T(t).…”

Section: Introductionmentioning

confidence: 99%

“…Atomization under isothermal conditions. Under isothermal conditions the process of entry of free atoms into a gas phase and their decrease can be described with the aid of a one-dimensional equation of diffusion with a source [8]. In our case, the function of the source density is described by superposition of two functions:…”

Section: Introductionmentioning

confidence: 99%

“…The sweeping out of the atomic vapor from the furnace is described by the expression (see, e.g., [9,10])…”

Section: Introductionmentioning

confidence: 99%

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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%

Section: Introductionmentioning

confidence: 99%

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Kinetic Model of Entry of Free Atoms into an Electrothermal Atomizer

et al. 2005

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“…Researchers have been working on development of methods for determining the kinetic parameters (activation energy and frequency factor) practically ever since electrothermal AAS was incorporated into routine analytical laboratory practice [1][2][3]. In each such study, they have proposed and implemented their own experimental and theoretical schemes, generally based on calculation of the coefficients in the Arrhenius equation from the results of measurement of the furnace temperature and a certain section of the analytical signal [4][5][6][7][8].Palladium-containing activated carbon is well recommended as a highly efficient sorbent for concentration of hydride-forming elements (As, Sb, Se, etc.) for electrothermal AAS analysis using the technique of dispensing as suspensions [9, 10].…”

mentioning

confidence: 99%

“…We determined the values of the activity energy (E a ) and the pre-exponential factor in the Arrhenius equation using the experimental measurement scheme we proposed. The method developed, taking into account previous methodological approaches [1][2][3][4][5][6][7][8], is based on determination of the temperature dependence of the rate of the atomization process, from the initial section of the measured analytical signals. We used the following assumptions:…”

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Kinetic studies of antimony and selenium atomization processes including a chemical modifier during their determination by electrothermal atomic absorption spectrometry

2006

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We have studied antimony and selenium atomization processes including a chemical matrix modifier (palladium-containing activated carbon) during their determination by electrothermal atomic absorption spectrometry. We have developed and fine-tuned an experimental setup for determining the kinetic characteristics (activation energy and frequency factor) for element atomization processes from measurements in the initial section of the analytical signal. We provide a rationale for the most likely mechanism for the interactions that occur. The results of the kinetic studies of the atomization processes showed that the modifier we developed was highly effective, as a result of formation of a thermally stable condensed system C-Pd-A (where A is the analyte).Introduction. Kinetic studies are a major method for studying mechanisms for atomization in electrothermal atomic absorption spectrometry (electrothermal AAS). They allow us to determine the optimal ways for rational correction of the conditions over the entire analytical cycle. Researchers have been working on development of methods for determining the kinetic parameters (activation energy and frequency factor) practically ever since electrothermal AAS was incorporated into routine analytical laboratory practice [1][2][3]. In each such study, they have proposed and implemented their own experimental and theoretical schemes, generally based on calculation of the coefficients in the Arrhenius equation from the results of measurement of the furnace temperature and a certain section of the analytical signal [4][5][6][7][8].Palladium-containing activated carbon is well recommended as a highly efficient sorbent for concentration of hydride-forming elements (As, Sb, Se, etc.) for electrothermal AAS analysis using the technique of dispensing as suspensions [9, 10]. Such a scheme has proven to be possible because of the high modifying activity of the composite. Further development of the electrothermal AAS method with dispensing of suspensions of carbonized materials into the graphite furnace requires new data on the nature of the interactions between the analyte elements and the sample matrix and the modifier sorbent used. We must note that such a procedure presumes the presence of large amounts of the material over the course of atomization (tenths of a milligram and several milligrams). This is the reason for the delay in recording the analytical signal. Obviously it is determined by the properties and mass of the solid residue in the graphite furnace, the design of the atomizer, the recording instrument, etc. Thus when dispensing suspensions of carbonized samples with a high organic matrix content, the time until appearance of the analytical signal depends on the carbonization temperature of the analyte samples [11]. The factors listed above are difficult to theoretically take into account when studying element atomization processes using the suspension dispensing technique.

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Model for the analytical signal in atomic absorption spectrometry with electrothermal atomization

et al. 2008

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543.422A method for verification of analytical measurements in electrothermal atomic absorption spectrometry using a phenomenological model for physicochemical atomization processes is discussed. The influence of the sample matrix on basic kinetic parameters of atomization such as the analyte free-atom formation energy and the atomization rate constant has been shown. The similarity of atomization kinetic parameters obtained by calibrating the spectrometer to those for samples under study can be used as a verification criterion for analysis.

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A kinetic model for an atomic absorption signal

Cited by 5 publications

References 12 publications

Kinetic Model of Entry of Free Atoms into an Electrothermal Atomizer

Kinetic Model of Entry of Free Atoms into an Electrothermal Atomizer

Kinetic studies of antimony and selenium atomization processes including a chemical modifier during their determination by electrothermal atomic absorption spectrometry

Model for the analytical signal in atomic absorption spectrometry with electrothermal atomization

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