Spectral interferences and background overcompensation in zeeman-corrected atomic absorption spectrometry : Part 1. The effect of iron on 30 elements and 49 element lines

The background compensation performance of a Zeeman corrector with the magnetic field acting on the graphite atomization cell was assessed for 30 elements and 49 element lines in an iron matrix. Two of the elements studied, gallium and zinc, are influenced by background overcompensation which introduces serious negative systematic errors. The overcompensation is due to the presence of iron lines close to the 287.4-nm gallium line and the 213.9-nm zinc line; when the magnetic field is on, the σ-components of the adjacent iron lines overlap at the position of the analyte line and a background, which is not present when the magnetic field is off, is recorded. When gallium and zinc are measured under the same conditions but with deuterium arc background correction, the adjacent iron lines cause positive systematic errors. These spectral interferences for gallium in the presence of iron can be avoided by doing the measurements at the 294.4-nm gallium line; the two lines have about the same sensitivity. When zinc is to be measured at the 213.9-nm line, with either type of background correction, the spectral interferences from iron can be avoided by careful selection of the graphite-furnace parameters. In addition to spectral interferences, iron also affects the sensitivity for both gallium and zinc.