A model for the determination of the activation energy and the order of release of the atom formation in electrothermal atomization atomic absorption spectroscopy

Abstract

A model for the atom formation in electrothermal atomization atomic absorption spectroscopy (ETAAS) is proposed. In this model, it is established that the activity of surface species is equated to the number of atoms with an energy value above the activation energy of the atom formation process. Dissipation of the analyte atoms is considered to be the result of diffusion, thermal expansion and redeposition processes. The new model based on Maxwell's theory can be used to determine the temperature-dependent activation energy and the order of release of the analyte atom formation process from one single absorbance–time profile and under non-isothermal conditions. An Arrhenius-type plot of Ln A i e + ∫ o t k 2iA i e dt T A p e −A i e + ∫ t t p k 2iA i e dt vs. 1/ T is used to determine the activation energy. Kinetics expressions are used to evaluate the order of the atom formation reaction, which can be deduced from the slope of the line obtained by plotting Ln dA i e dt +k 2 i A i e A p e −A i e + ∫ t t p k 2 i A i e dt T m+0.5 vs. Ln A p e −A i e + ∫ t t p k 2 i A i e dt T − E 0 kT . All calculations were carried out using the experimental absorbances data. A comparison with the previously developed models using the same earlier published experimental data sets for Cu, Ni and Au is made. The agreement found between the results derived from this work and those earlier published is satisfactory.