Abstract
In order to obtain additional insight into the release mechanism of the metals in electrothermal atomization atomic absorption spectrometry, a quantitative relation between the heat of vaporization and the size of the released particles is proposed on the basis of the Kelvin equation. The applicability of the equation for the investigation of silver and gold vaporization is demonstrated and the limits in which the model is valid are determined. According to the present considerations the activation energy could be equal to the heat of vaporization of the silver and gold droplets. An explanation of the observed dependence of activation energy on analyte mass is given. The proposed relation provides a possibility for definition and evaluation of an “effective” radius/size of the droplets on the basis of their heat of vaporization. A correlation between the mass of the injected sample and the “effective” radius of the droplets, obtained at higher temperature is found. The minimum and maximum “effective” radii of the droplets, following the proposed equation are calculated for Ag on pyrolytic graphite coated electrographite (PGC) and Au on PGC, uncoated electrographite (EG) and glassy carbon (GC) tubes. The results obtained are indirect evidence for the island structure of precursor metal layer and for the existence of silver and gold microdroplets on the graphite support.
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