Abstract

Aerosol characteristics when nebulizing nitric acid solutions and water were measured for two spray chambers commonly employed in ICP-AES: a double pass and a cyclonic type. The results indicated that the aerosols leaving the spray chamber (tertiary aerosols) were finer for a 0.9 mol l ⁻¹ nitric acid solution than for water, with the extent of this change more pronounced for the double pass spray chamber than for the cyclonic one. For the double pass spray chamber, the most important change in aerosol characteristics induced by nitric acid with respect to water was produced at the exit of the central tube. The ICP-AES emission signal data revealed that the nitric acid steady state interference was more severe for the double pass spray chamber than for the cyclonic one. Therefore, the measurement of tertiary aerosols could be considered as an appropriate diagnostic to estimate the extent of matrix effects. Several experiments were performed to elucidate the mechanism responsible for the acid effects, showing that they cannot be attributed to a single source. The data obtained revealed the complexity of the steady matrix effects induced by inorganic species. The influence of the spray chamber design on the acid transient effects was also studied. It was observed that these effects were similarly more pronounced for the double pass than for the cyclonic spray chamber. The temperature of the spray chamber walls played a significant role on the magnitude of the acid transient effects.