ELECTROTHERMAL ATOMIZATION OF LEAD FROM DIFFERENT ATOMIZER SURFACES

Atomization of lead from pyrolytic graphite-coated, zirconium-coated and palladium-coated graphite tubes has been investigated following the direct deposition of the analyte solution and/or the trapping of the gaseous hydride. Comparison of appearance temperatures, kinetic orders and activation energies for the atomization of lead shows that the mode of sample introduction does not appear to play any significant role in governing analyte release energetics, out the nature of the atomizer surface has an apparent effect on the mechanism of atomization. A first-order kinetic release occurs from the pyrolytically coated graphite tube, indicating the analyte desorbs from the surface as highly dispersed atoms. The activation energy (E(a)) of 72 +/- 4 kcal mol-1 is calculated, which may represent the lead-graphite interaction energy. For the zirconium-coated graphite tube, a fractional order between zero and 1/3 with lower E(a) values (45-48 kcal mol-1) implies the release of lead from three-dimensional structures in the form of ''caps'' or micro-droplets, showing weak lead-zirconium carbide interaction. From a palladium-coated graphite tube, the obtained first-order kinetics with much larger E(a) values (100-124 kcal mol-1) for the atomization of lead suggests relatively strong interaction occurring between lead and palladium.