Investigation of the mechanism of the electrothermal atomization of platinum in a graphite furnace from aqueous solutions and serum samples

Abstract

The mechanism of platinum atomization in electrothermal graphite atomizers was investigated in aqueous solutions and in serum samples. The methods of Rojas-Olivares and Yan et al., representing a chemical approach to the investigation of atomization mechanisms, as well as the physical approach developed by L’vov, were used. The activation energies for 1–8 ng of Pt in aqueous solution, calculated with use of the first two methods, increased with the increase of Pt mass, ranging from E_a = 245 ± 13 kJ mol⁻¹ to E_a = 387 ± 11 kJ mol⁻¹. The change of ratio T_app/E from 6 to 4 with increasing Pt masses suggests that the atomization mechanism of Pt is progressively changing from an adsorption to an evaporation process. In serum samples, for all the Pt masses examined, one mechanism is observed. The calculated activation energy had a mean value of E_a = 203 ± 8 kJ mol⁻¹ and is ascribed to an atomization mechanism via thermal desorption of Pt atoms from the carbon residue produced by the pyrolysis of the organic matrix. Confirmation of the above conclusions is provided by the physical method of L’vov, as the ratio T_app/E was approximately 8 in the presence of serum matrix. All the methods used gave consistent conclusions rendering them more reliable.