<p>The performance of different types of nebulisers: Vulkan direct injection nebuliser (Vulkan DIN), direct injection high efficiency nebuliser (DIHEN), microconcentric nebuliser coupled to cyclonic or double pass spray chamber (MCN-C or MCN-DP, respectively) was investigated and compared when used for sample introduction to ICP-MS or ICP-OES. With ICP-OES, in axial viewing mode, intensity distributions across the radius of the plasma (radial intensity profiles) were determined for different spectral lines with Esum 1.85-15.41 eV to determine fundamental plasma properties for various matrices using Vulkan DIN and MCN-C. The results showed that with the MCN-C the ionisation temperature (Tion) was about the same across the measured region of the plasma (±3.0 mm) whereas with the Vulkan DIN the Tion was significantly lower in the centre of the plasma. A large deviation from local thermodynamic equilibrium, as well as deteriorated stability, was observed for the plasma when using the Vulkan DIN.</p><p>With ICP-MS noise power spectra (NPS) were generated to identify sources of noise. NPS showed that the magnitude of white noise for the tested sample introduction systems decreased in the following order: Vulkan DIN > DIHEN > MCN-C > MCN-DP. This order follows the decrease of mean droplet size and span of the size distribution, indicating that the white noise is caused by spatial and temporal non-uniform desolvation and ionisation. Another source of noise arose from the peristaltic pump and the magnitude of pump interference noise decreased in the following order: DIHEN > MCN-C/DP > Vulkan DIN. Mains power interference noise and 1/f noise were lower for the direct injection nebulisers compared to the spray chamber systems. The contribution or effects of these noise components on relative standard deviations of steady-state ion-count rate and isotope ratio measurements is discussed in this thesis.</p><p>Aerosols generated by the Vulkan DIN and the DIHEN were also directly characterised using Particle Dynamic Analysis. The Vulkan DIN produced particles with a mean diameter of ~30 µm and a size distribution between 2-80 µm. With the DIHEN the corresponding values were ~11 µm and 1-40 µm, respectively, with a few particles at 55-78 µm. The mean velocity of particles from the Vulkan DIN was ~10 m s-1 and from the DIHEN ~18 m s-1. The lower velocity allows longer residence time counteracting the effects of the larger droplet size.</p>
| Identifer | oai:union.ndltd.org:UPSALLA/oai:DiVA.org:umu-671 |
| Date | January 2006 |
| Creators | Goitom Asfaha, Daniel |
| Publisher | Umeå University, Chemistry, Umeå : Kemi |
| Source Sets | DiVA Archive at Upsalla University |
| Language | English |
| Detected Language | English |
| Type | Doctoral thesis, comprehensive summary, text |
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