AN APPROACH TO THE DETERMINATION OF THE KINETIC-PARAMETERS FOR ATOM FORMATION IN ELECTROTHERMAL ATOMIC-ABSORPTION SPECTROMETRY

A method for the simultaneous determination of the kinetic order, activation energy and frequency factor for atom formation from one single absorbance signal under normal analytical conditions in electrothermal atomic absorption spectrometry (ETAAS) has been investigated. Both computer simulation techniques, with known kinetic parameters of atom formation, and ETAAS experiments are employed to examine the validity of the present method and comparison is made among several methods so as to elucidate the merits of the present method. The results show that the activation energy values obtained at lower temperatures by the previous methods and by the present method are almost identical. However, the Arrhenius plots obtained by the previous methods often bend at higher temperatures while those obtained by the present method exhibit much wider linearity. The curvature may result from the assumption of the first order kinetics for atom formation, the steady state approximation and/or multiple release mechanisms. The present method has been successfully applied to the determination of the kinetic parameters for the atomization of copper and manganese. The values of the kinetic order, activation energy and frequency factor, are found to be 1.07 +/- 0.04, 40 +/- 2 kcal mol-1 and (3.2 +/- 1.1) x 10(5) s-1 for copper, and 1.00 +/- 0.04, 45 +/- 2 kcal mol-I and (2.5 +/- 1.2) x 10(5) s-1 for manganese, respectively. In addition, a method for the simultaneous determination of the diffusion coefficient of gaseous atoms and its temperature dependence from the decay portion of one single absorbance signal has been proposed.