ELIMINATION OF SPECTRAL INTERFERENCES IN INDUCTIVELY COUPLED PLASMA ATOMIC EMISSION-SPECTROSCOPY USING ORTHOGONAL POLYNOMIALS

Orthogonal polynomials have been applied to correct for spectral interferences in ICP-AES. The emission spectra of many analytes measured over fairly wide wavelength ranges have characteristic normal probability distribution profiles (quadratic pattern) centering on the prominent line of each element. The emission spectra of many interferents (with the exception of direct line overlap) display more or less linear shapes over the same analyte wavelength range. Accordingly, a quadratic polynomial fitting results in coefficient values that relate largely to the concentration of the analyte and negligibly to the concentration of interferents. The method has been demonstrated to cancel the interference caused by the presence of 1000 mg l concentrations of Ca, Mg, Al and Fe in the analysis of selected elements (Cr, Cu, Mn, P, Zn, S and Pb) at their most sensitive prominent lines. The results indicate not only the efficacy of the proposed method for eliminating such interferences, but also its superiority over the currently used two- and three-point correction procedures. © 1990.