Investigation and quantification of spectroscopic interferences from polyatomic species in inductively coupled plasma mass spectrometry using electrothermal vaporization or pneumatic nebulization for sample introduction

A new method for quantification of spectral interferences based on analyte isotope ratio measurements in the presence of various concentrations of a specific matrix is presented. Within the method, a tolerance level is used, defined as the matrix concentration at which the ratio between analyte isotopes with and without interferences is altered by 10% compared to a pure water reference standard, normalized with respect to the analyte concentration in the solutions. This can be used to estimate the lowest analyte concentration which can be determined with a defined accuracy in the presence of a known concentration of a specific matrix. Regarding spectroscopic interference effects, comparative results for sample introduction into the ICP-MS by electrothermal vaporization, ETV, and nebulization are presented for common matrix - (Ca, Na, K, CI, P, O) and analyte (Cr, Ni, Cu, As, Se) elements. With the exception of the spectral overlap of P-31(2)+ on Ni-62(+), spectroscopic interferences were reduced by 1-2.5 orders of magnitude when using ETV for sample introduction. Reasons for the increase in the spectral interference of P-32(2)+ on Ni-62(+) are discussed. For sample introduction by nebulization, it was found that spectral interferences from CaO+ on Ni-58(+) and Ni-60(+) were reduced in the presence of phosphate. (C) 1998 Elsevier Science B.V. All rights reserved.