No abstract

No abstract

No abstract

No abstract

Density functional theory in the plane wave basis set is used to study As adsorption on the Pd(111) surface in order to determine the action of a palladium chemical modifier used in electrothermal atomic absorption spectrometry (ETAAS). The calculated heat of desorption of the arsenic atom is 435 kJ/mole, which corresponds to the activation energy of arsenic atomization of 439 kJ/mole (in the range of high temperatures T > 1828 K), obtained by ETAAS. Based on the calculated data, the action of the palladium modifier for the determination of As is assumed to be controlled by the process of chemisorption.Electrothermal atomic absorption spectrometry (ETAAS) is used for the quantitative elemental analysis, primarily to determine the concentration of metals in the environment (soil, sewage), food, and raw materials, etc.[1]. The sample mostly consists of organic compounds, the so-called matrix that includes chemical elements to be analyzed. In order to avoid interference from matrix signals the sample is heat-treated (pyrolysis) in the presence of metal modifiers. The metal modifier binds the element under study and prevents its evaporation during pyrolysis, i.e. eliminates losses before atomization and measurement of the analytical signal [2].Palladium modifiers are often used to determine the concentration of arsenic by ETAAS [3][4][5]. Metal modifiers are believed to form stable condensed solutions with the analyte [2,6]. It prevents arsenic losses in the form of volatile compounds such as As 2 , AsO, or AsC [7]. Moreover, platinum metals catalyze the oxide reduction reaction in the graphite furnace (electrothermal atomizer system), and they also are good sorbents of gaseous hydrides (AsH 3 , SbH 3 , SeH 2 , etc.) [8,9]. The reverse process of desorption, i.e. As evaporation, is hindered by a high energy barrier [10] that may be attributed to the ability of the metal modifier to chemisorb the analyte [11][12][13]. The optimum ratio of masses of the analyzed element and metal modifier is 10 -3 -10 -5 , which complicates the use of traditional physical and chemical methods to study new compounds and high-temperature processes with their presence. In this work, quantum chemical methods are used to simulate arsenic adsorption on the Pd metal surface. The calculation results are discussed taking into consideration the experimental data on the ETAAS determination of arsenic.