Optimization of analytical performance of a graphite furnace atomic absorption spectrometer with Zeeman-effect background correction using variable magnetic field strength

This paper describes a graphite furnace atomic absorption spectrometer of the third generation with Zeeman-effect background correction and variable magnetic field strength. Compared to earlier generations it is focused on magnetic field strength control and technical and analytical performance parameters. The Zeeman ratios for 10 elements at different magnetic field strengths were determined. The capability of increasing the magnetic field strength up to a maximum of 1.0 T allows the analytical sensitivity for Cu to be improved by up to 38%, resulting in an enhanced Zeeman ratio, and two-folds increase of the linear working range. Alternatively, the introduction of the 3-field mode - measurement at zero, maximum and a medium magnetic field strength - allows the sensitivity to be adapted for higher analyte concentrations. With this mode, Cu, Fe and Zn were determined in serum, with analyte contents in a concentration range common for flame atomic absorption spectrometry. The results were in good agreement with the expected values. The dynamic mode combines the sensitive measurement mode of graphite furnace atomic absorption spectrometry with the reduced-sensitivity 3-field mode. The present work demonstrates how this mode enables to extend calibration over 3 orders of magnitude for Pb. (C) 2003 Elsevier B.V. All rights reserved.