Comparative Study of Several Nebulizers in Inductively Coupled Plasma Atomic Emission Spectrometry: Low-pressureversus High-pressure Nebulization

Abstract

Five nebulizers for use in ICP-AES were compared. Two of them work at low pressure, a Meinhard and a V-groove nebulizer (VGN), and three at high pressure, a single-bore high-pressure pneumatic nebulizer (SBHPPN), a hydraulic high-pressure nebulizer and a thermospray (TN). The comparison was made using three solvents, water, ethanol and butan-1-ol, using the sample uptake rate ( Q _l ) as a variable and studying its influence on drop size distribution, analyte transport rate and analytical behaviour, i.e. , emission intensity and limits of detection (LODs). The sample introduction system includes a desolvation unit. The Sauter mean diameters of the primary aerosols generated by the high-pressure nebulizers (HPNs) are between 1.5 and 5.8 times lower than those generated by the low-pressure nebulizers (LPNs), this reduction being more noticeable at high liquid flow rates. In addition, at high liquid flow rates, HPNs achieve higher analyte transport rates (between 2.4 and 19 times higher), higher emission signals (up to 1.8 times for methanol and up to 4.5 times for water, using the Mn II 257.610 nm line) and lower LODs for nine elements than the LPNs. Among HPNs, the SBHPPN gives rise to the best results at low Q _l ( i.e. , 0.6 ml min ^-1 ), whereas at high Q _l ( i.e. , 1.2 ml min ^-1 ) the results are similar for all three HPNs when using methanol and butan-1-ol. With water, at high Q _l , the TN gives the best results. For all the nebulizers tested, organic solvents (methanol and butan-1-ol) provide better results than water, the relative improvement being more important for LPNs ( e.g. , with VGN at 1.2 ml min ^-1 , the improvement with methanol over water for Mn II is around sixfold) than for HPNs ( e.g. , when SBHPPN is used at 1.2 ml min ^-1 for Mn II this improvement is 4.5-fold).