Abstract
D.Phil. (Chemistry)
In order to optimise the parameters for graphite tubes used for electrothermal
atomic absorption spectrometry a good understanding of the
factors that influence the efficiency of the atomisation process is
necessary. The most important of these factors are the temperature
surroundings of the analyte. Consequently, a model was developed to
calculate the spatial and temporal variations of the wall temperature
of the tube.
Reliability of the calculations was ensured by determining some
graphite parameters experimentally. Normal laboratory conditions
could therefore be simulated precisely. There were some problems
associated with the actual measurement of wall temperatures. After
these had been investigated and solved, it was possible to correlate
and verify the calculated temperat~re values with the experimentally
measured ones.
While it is likely that the analyte evaporates as such (or in modified
forms) from the walls of the tube, the actual atomisation process most
probably takes place in the gas phase. It is therefore the gas temperature
that controls atomisation. In view of this a gas temperature
model was developed by means of which spatial and temporal temperature
data within the atomiser could be calculated. Together with the calculations
of wall temperatures already mentioned, this presents for
the first time the possibility of calculating temperatures, both
spatially and temporally, at any point within the atomiser during the
heating cycle.
With the above information, the nature of atomisation processes can be
studied. In this work, attempts were made to study the mechanism by
which- the use of a platform placed within the atomiser eliminates
interferences. Contrary to the literature, it was found that this can
not be attributed to stabilized temperature surroundings.