Monte Carlo Study of the Relationship between Atom Density and Absorbance in Electrothermal Atomizers

This work attempts to evaluate the generalized assumption that the electrothermal atomization absorbance signal is proportional to the gas-phase density throughout the transient profile. Spectral line shape considerations (i.e., Voigt profile and hyperfine structure) are introduced into a Monte Carlo simulation model to exploit the time and spatial density and temperature information made available from the simulation. The absorbance is found to be nearly proportional to gas-phase density at low analyte densities—in agreement with generalized assumptions. At higher concentrations the similar linewidths for the absorption and emission profiles reduce the absorbance signal and linear dynamic range. In general, furnace nonisothermality does not produce spectral results noticeably different from those observed with isothermality heated tubes. The temperature-dependent spectral changes for a nonisothermally heated furnace can be closely approximated in most cases by considering only the temperature at the center of the tube.