Determination of phosphorus in steel with a stabilized-temperature graphite furnace and zeeman-corrected atomic absorption spectrometry

The determination of phosphorus in steel by graphite furnace a.a.s. is plagued by a spectral interference from the iron matrix which results in overcompensation when a continuum-source background corrector is used. Zeeman background correction using an alternating transverse magnetic field at the furnace eliminates this problem and allows a routine determination of phosphorus down to 0.002% in steel. Lanthanum is an effective matrix modifier for the phosphorus determination, but its enhancing effect depends largely upon the tube material used and the sample matrix. A 0.2% lanthanum solution was found to be optimum. The stabilized-temperature platform furnace concept allows an interference-free determination of phosphorus in steel, down to 0.002%, directly against aqueous standards. Atomizing the sample from a pyrolytic graphite platform in an uncoated graphite tube provides the optimum environment for a phosphorus determination.