INFLUENCE OF EMISSION FROM THE FURNACE WALL ON ZEEMAN ATOMIC-ABSORPTION SPECTROMETRIC SIGNALS

About 8% of the radiation emitted by the wall of the graphite furnace consists of a.c. components, independent of the total amount of furnace emission that reaches the detector. The ratio of the signals measured with Zeeman-effect background-corrected atomic absorption spectrometry (ZAA) and atomic absorption spectrometry without Zeeman-effect background correction (AAS), depends on the contribution of the furnace emission intensity to the measured intensities. The ratio of the absorbances, ZAA:AAS, is equal in peak height and in integrated absorbance in the absence of furnace emission. When furnace emission is present, the ZAA:AAS ratio is increased. The enhancement is much more pronounced in integrated absorbance than in peak absorbance. The a.c. components of the radiation emitted by the furnace wall cause systematic errors in the ZAA signal and also contribute to the noise. High-frequency modulation of the hollow-cathode lamp was applied to eliminate the influence of furnace emission on Zeeman-effect AAS signals.