EVALUATION OF CALIBRATION METHODS FOR ZEEMAN GRAPHITE-FURNACE ATOMIC-ABSORPTION SPECTROMETRY USING COMPUTER MODELING

Computer modeling was used to compare calibration curves and relative concentration errors for normal, linearized, and three-field Zeeman GF -AAS. The model assumed that either photon shot noise or the combinati on of photon shot and analyte fluctuation noise were limiting and that the sole source of nonlinearity was stray light. For absorbance, the calibration range and the relative concentration error for all three m ethods are almost identical. The difference is a reduced-sensitivity c urve for three-field Zeeman, which offers a relative concentration err or advantage in the concentration region where the most sensitive curv e rolls over. For integrated absorbance, the sum of absorbances over t he analytical peak, linearized Zeeman provides a significant relative concentration error advantage over the other methods at the high conce ntration end of the calibration curve. The calibration range is effect ively extended by at least 1.5 orders of magnitude. This advantage ari ses from integration of absorbances which have a linear relationship t o concentration. At high concentrations, absorbances computed for norm al and three-field Zeeman are nonlinear with respect to concentration. Three-field Zeeman offers no advantage over normal Zeeman for integra ted absorbance.