UV spectrometry (187–380 nm) with charge coupled device (CCD) detection was used to study the evolution of absorption spectra during the
vaporization of various species in the pyrocoated graphite furnace, with electrodeposited Ir and Rh as modifiers. In order to mimic a typical matrix
composition, various salts of aluminum, manganese, copper, magnesium, sodium, and lead were used in microgram amounts. Changes in spectra
and vapor release rate, along with aging of the tubes in the repetitive temperature cycles, were observed.
Compared to the unmodified pyrocoated tubes, the presence of Ir or Rh causes a significant reduction in the vaporization efficiency, especially
for microgram amounts of copper and aluminum introduced as nitrates, and manganese introduced as a sulfate. The vaporization efficiency, for
magnesium and sodium as chlorides, and for lead as a sulfate, remained unchanged. Interestingly, the aging of the tubes was accompanied by
partial restoration of the spectral characteristics for unmodified tubes. For example, with unmodified pyrocoated tubes, the vaporization spectrum,
appearing as a consequence of the decomposition of aluminum nitrate, consisted of Al2O bands overlapped by Al atomic lines. In the freshly
modified tubes, intensities of those lines and bands were substantially reduced, and in this case, the dominance of AlO molecules was observed.
The efficiency of vaporization of aluminum species increased in the aged modified tubes.
The scanning electron microscopy (SEM) images of the modified surfaces for the new and aged tubes indicated that aging of the tubes is
accompanied by the destruction of the pyrocoating, formation of pyrographite shells around the areas where the modifier was electrodeposited,
and finally, complete substitution of the metal on the graphite surface by pyrographite debris.
| Identifer | oai:union.ndltd.org:netd.ac.za/oai:union.ndltd.org:tut/oai:encore.tut.ac.za:d1000794 |
| Date | 26 August 2006 |
| Creators | Bulska, E, Piascik, M, Katskov, D, Darangwa, N, Grotti, M |
| Publisher | Elsevier |
| Source Sets | South African National ETD Portal |
| Language | English |
| Detected Language | English |
| Type | Text |
| Format | |
| Rights | © 2007 Elsevier B.V. |
| Relation | Spectrochimica Acta |
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