Spectral Interferences in the Determination of Phosphorus in Steel by Inductively Coupled Plasma Emission Spectrometry with an Echelle Monochromator

Spectral interferences in the determination of phosphorus in steel by inductively coupled plasma emission spectrometry is studied by using a computer-controlled, scanning echelle monochromator. There is no direct overlap of an iron line on the phosphorus analysis line, P(I) 213.618 nm, although several iron lines that have not been reported in the literature are observed near the phosphorus line. Scatter light, recombination continuum, and the wing of the Cu(II) 213.598 nm line cause background shift, but the interference can be eliminated by using wavelength modulation and lock-in amplification. The NO band interference arising from the entrainment of air into the plasma is observed when the outer gas flow rate is below 10 liters/min. The detection limit of phosphorus in steel is 0.0006% in the present method.