Characterization of trace metal desorption using electrothermal atomic absorption spectroscopy
The desorption characteristics of several metals have been studied using electrothermal atomic absorption spectroscopy (ETAAS). Activation energies and orders of release obtained from the atomic absorption profiles provided the main tools to draw conclusions about the different systems. Different factors affecting the absorption profiles were studied. Vaporization was carried out from different substrates including graphite, Ta and alumina. Different heating rates, drying temperatures and thermal pretreatment temperatures were studied. Chemisorption of gases onto the graphite prior to the sample deposition and roughening of the substrates surface using abrasives were also evaluated. ETAAS data provides information concerning the degree of metal-substrate interaction which is elemental dependent. Changes in activation energies as a result of variations in the thermal treatment of the sample revealed changes in the distribution of the analyte on the surface. The metal geometry and its distribution on the surface was also affected by changes in the substrate. Metals such as Ag and Au seemed to move on the surface and disperse to smaller particles when the temperature of the substrate reached the Tammann temperature for the respective metal. Given the potential of ETAAS to provide surface information a tube-in-tube atomizer was designed to make the technique more amenable for this type of investigation. Metal migration into different types of graphite was studied. Metals appeared to migrate several microns through imperfections on the substrate surface. The main effect of this migration on the atomic absorption profiles seemed to be an increase in tailing of the back edge. Finally, several methods used to evaluate kinetic parameters from ETAAS data were compared. One of the methods does not seem to discriminate order of release different than unity. However, the others did yield reasonable results for the metals studied with good correlations among them.
- Research Organization:
- Texas Univ., Austin, TX (United States)
- OSTI ID:
- 7102153
- Country of Publication:
- United States
- Language:
- English
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