TOPOLOGY AND VAPORIZATION CHARACTERISTICS OF PALLADIUM, COBALT, MANGANESE, INDIUM, AND ALUMINUM ON A GRAPHITE SURFACE USING ELECTROTHERMAL ATOMIC-ABSORPTION

Time and spatially resolved absorbance profiles, concentration studies, and aerosol deposition vs manual pipetting studies have been obtained for Pd, Co, Mn, In, and Al in 0.5% nitric acid. The activation energies of release for Pd, Co, and Mn are 44 +/- 3, 36 +/- 3, and 43 +/- 6 kcal/mol, respectively. Two activation energies were obtained over the course of release for In using manual pipetting: 57 +/- 7 and 33 +/- 5 kcal/mol. A strong Pd-graphite and Co-graphite interaction accounts for the characteristically broader half-widths and spatially nonuniform atom distribution on the rising portion of the peak. Data suggest that Pd and Co desorb from the graphite surface as individual atoms, which results in an apparent first-order release. The relatively weak metal-graphite interactions observed for In account for the narrower half-widths and a relatively uniform atom distribution within the furnace during atomization. For In, the formation of aggregates with desorption occurring from the aggregate surface is proposed as one of the generation mechanisms. In the case of Mn, vaporization occurs from aggregates of a Mn compound on the surface. However, an apparent first-order release is observed. Finally, Al is characterized by uniquely rapid generation from aggregates and undergoes gas-phase reactions.