EXTENSION OF THE DYNAMIC-RANGE IN AC ZEEMAN ELECTROTHERMAL ATOMIC-ABSORPTION SPECTROMETRY

In electrothermal atomic absorption spectrometry (ETAAS) the dynamic range of analytical curves is limited to 2-3 orders of magnitude, depending on the analyte element. Zeeman background correction further reduces the analytical range for elements that show a significant contribution of sigma-component absorption to the measurement of the background absorption at maximum magnetic field strength. The 3-field a.c. Zeeman system offers at best a factor of 5 extension of the dynamic range in comparison with the conventional 2-field a.c. Zeeman system when peak absorbance is used and only a factor of 2 using integrated absorbance. The slope of the 3-field analytical curve can be selected by adjusting the intermediate field strength. However, acceptable precision of the measured analyte concentrations over the broader concentration range is obtained only when the slope of the 3-field analytical curve is reduced with a factor of about 2-3 in comparison with the corresponding 2-field Zeeman analytical curve. Extension of the dynamic range of the analytical curve is obtained at the cost of less precision for the measured analyte concentrations.