The role of the nebulizer on the sodium interferent effects in inductively coupled plasma atomic emission spectrometry

Abstract

The role of the nebulizer on the sodium chloride interferent effects in ICP-AES was investigated. Three different pneumatic nebulizers coupled to a cyclonic spray chamber were investigated: a V-groove (VGN) and two new pneumatic concentric nebulizers specifically designed to work with saline solutions (the 'Seaspray' nebulizer, SSN, and experimental nebulizer, EN). The effect of the salt concentration on the characteristics of the aerosols generated by the nebulizers (primary aerosols) and those at the exit of the spray chamber (tertiary aerosols) on the transport parameters and on the analytical figures of merit in ICP-AES were evaluated. The characteristics of the primary aerosols were related to their critical dimensions and were independent of the solution salt concentration. Solvent and analyte transport rates were related to the characteristics of the primary aerosols. Thus, the SSN provided the highest solution transport rates followed by the EN and VGN. The Mn II emission signal correlated quite well with transport parameters. When the salt concentration increased, an interference effect on the ICP-AES emission signal was observed. This effect was related to the nebulizer employed. Thus, for the SSN, the effect of the sodium chloride on the emission signal was different for the ionic and atomic lines. For the remaining nebulizers, a depressive effect of the salt concentration on the emission signal was always observed irrespective of the line considered. The magnitude of the interference was different for each nebulizer and was related to the amount of solvent transported to the plasma. In general terms, by increasing the salt concentration, poorer signal precision and limits of detection were obtained. These results confirm the importance of sustaining robust plasma conditions to reduce the sodium chloride interferences.