Investigation of matrix effects in inductively coupled plasma-atomic emission spectroscopy using laser ablation and solution nebulization - effect ofsecond ionization potential

Plasma-related non-spectroscopic matrix effects of 31 elements in inductive ly coupled plasma (ICP)-atomic emission spectrometry were investigated usin g both laser ablation and solution nebulization as sample introduction tech niques. Matrix effects were studied by monitoring the excitation conditions of the plasma using the ionic to atomic spectral line intensity ratios of zinc and magnesium. A new kind of matrix interference was found in the ICP that appears to be related to matrices with elements of low second ionizati on potential. The matrix effects do not correlate with the first ionization potential of the element. Only those matrix elements with low second ioniz ation potential showed severe matrix effects. Increasing the forward power of the ICP or replacing the carrier gas with a 50%/50% argon-helium mixture did not significantly reduce this matrix effect. However, using 100% heliu m as the carrier gas greatly reduced the extent of this matrix effect, sugg esting that argon is involved in the interference mechanism. The interferen ce mechanism may involve interactions between doubly-charged matrix ions an d argon species. (C) 2001 Elsevier Science B.V. All rights reserved.