A THEORETICAL INVESTIGATION OF ISOTOPE ABSORPTION SPECTROMETRY: COMPUTER SIMULATIONS

A computer model that can calculate absorbances for atomic absorption spectrometry involving multi-isotopic elements is presented. The validity of the model calculations is verified by close matching of calculated absorbances with independently measured experimental absorbances aimed to determine isotope abundances of Li. The model is able to reveal behavior of atomic absorption experimental systems which are difficult to observe directly unless the experiments are performed with extreme care.;For four selected elements (Ga, Cu, Pb and Hg), with different hyperfine structures, isotope shifts and number of isotopes, the optimum experimental conditions and the strategies to be used for isotope abundance determinations using flame atomic absorption spectrometry are delineated.;Also, for situations where the isotopic compositions of analytes and standards are different from one another, the possibility of obtaining inaccurate results in quantitative elemental analyses is demonstrated. For the four selected elements, the experimental conditions (the elemental concentrations and the type of the flame absorption cell) which do not introduce errors into analyses are presented.;For the four elements referred to above, the magnitude of analytical error and the maximum absorbance that do not introduce error into analysis are also determined for several analyte isotopic compositions, elemental concentrations and different experimental conditions.;The significance of the dependence of isotope shifts and hyperfine and fine structure separations of spectral lines on the sensitivity of isotope abundance determinations using flame atomic absorption spectrometry are demonstrated. Further, the effects of concentrations of all isotopes and the flame parameters (line broadening parameter and collisional shift of absorption lines) on the ability to discriminate among isotopes for a given experimental system are shown.;Finally, the influence of the Zeeman effect of emission or absorption spectral lines on the sensitivity of isotope abundance determinations and the magnitude of analytical error are evaluated. For the selected elements, the optimum field strengths and the configurations which can increase the sensitivity of isotope abundance determination and decrease the analytical error are determined.