Mechanism of action of a palladium modifier

The mechanism of low-temperature migration of analytes onto a palladium modifier and the mechanism of analyte retention on palladium in the pyrolysis stage have been interpreted on the basis of the method of absolute reaction rates and the mechanism of dissociative evaporation of solids. As has been shown previously by the author, the decomposition of solids, in particular, metal nitrates, occurs through the congruent gasification of all reaction products, irrespective of their saturated pressure (with the simultaneous condensation of low-volatility species). In the interval between gasification and condensation, these species could diffuse for some distance from the primary site. An application of the method of absolute reaction rates (the Hertz-Langmuir vaporization models) to the kinetics of analyte release in the presence of a palladium modifier permits the interpretation of the retention mechanism as dissociative chemisorption. The experimental data from the literature (the appearance temperatures and activation energies for Ag, As, Au, Bi, Cd, Cu, Se and Tl) were used in these calculations.