Hollow-cathode lamp-excited inductively coupled plasma atomic-fluorescence spectrometry: performance under compromise conditions for simultaneous multi-element analysis

Abstract

The plasma operating conditions required for the simultaneous analysis of dissimilar elements (refractory, easily dissociated and easily ionised) by hollow-cathode lamp-excited inductively coupled plasma atomic-fluorescence spectrometry (HCL-ICP-AFS) were studied. The r.f. power to the plasma and the carrier gas flow-rate required for simultaneous analysis degraded the detection limits only about four-fold or less for most elements, except the alkali metals, for which the degradation may be as much as two orders of magnitude. Using these conditions, matrix interferences due to solute vaporisation effects are small or absent. Detection limits and matrix interferences are independent over a wide range of observation heights in the plasma. The use of an ultrasonic nebuliser with aerosol desolvation increases the sample transport efficiency to the plasma about eight-fold, and enables correspondingly better detection limits to be achieved than using pneumatic nebulisation. The inclusion of solvent desolvation prevents cooling of the plasma, which, in turn, greatly reduces or eliminates matrix interferences due to solute vaporisation effects.