Absorbance vs. time curves at high heating rates in electrothermal atomic absorption spectroscopy

The absorbance vs. time curves that can be obtained in electrothermal atomi c absorption spectroscopy with special atomizers and high heating rates can show a very steep increase of the signal from the baseline at the beginnin g of the atomization step, followed by a more or less extended flat region and by an exponential decay. This type of curve can be mathematically descr ibed by simple equations if rather drastic assumptions are made, i.e. if th e atom supply is a delta function, if the absorbing species are homogeneous ly distributed in a plane at the center of a container of constant cross-se ction, and if the atom removal occurs only by diffusion. In this paper, som e experimental curves are presented which are in satisfactory agreement wit h the theoretical model, thus supporting the claim that, with our atomizati on system and power supply, the existence of the flat region is indeed just ified. With a new atomizer, specifically designed, it is possible to measur e the diffusion coefficient of atoms in a gas at high temperature. However, for accurate measurements, the model must be refined and better measuremen ts of the temperature of the atomizer must be obtained. (C) 2000 Elsevier S cience B.V. All rights reserved.