EFFECT OF SODIUM DURING THE AEROSOL TRANSPORT AND FILTERING IN INDUCTIVELY-COUPLED PLASMA-ATOMIC EMISSION-SPECTROMETRY

Robust conditions, i.e. high R.F. power and low carrier gas flow rate were used to minimize the role of the plasma and to emphasize the cont ribution of the sample introduction system in the effect of Na in ICP- AES. Two combinations of pneumatic nebulizers and spray chambers were selected to obtain different Na effects, A conespray nebulizer was use d with a cyclone spray chamber, and a cross-flow nebulizer was coupled to a double-pass spray chamber. A decrease in the ICP-AES analyte sig nal was observed with Na solutions under so-called robust conditions, irrespective of the sample introduction system employed. The cross-flo w nebulizer associated with the double-pass spray chamber was more sen sitive to Na presence than the other combination. These observations c an be partially explained by a decrease in the solvent transport rate observed in presence of Na. It has been found that, in every case, the presence of Na did not modify the characteristics of the primary aero sol, while the tertiary aerosol is significantly modified. Finer dropl ets were obtained at the exit of the spray chamber when Na was present . Also, recirculation of the aerosol led to a significant element enri chment of the largest droplets for the Na solutions. It can be conclud ed that the effect of Na occured during the aerosol transport and filt ering through the spray chamber. (C) 1998 Elsevier Science B.V.