Nebulizer geometry

A theoretical study of factors which affect pneumatic nebulizers (nebulizer geometry, capillary diameter, temperature fluctuations, gas pressure, solution viscosity, etc.] has been published by Heineman (24). Ultrasonic nebulization (which produces both smaller droplets and a narrower droplet size distribution] continues to attract attention (93, 95). 

For many years pneumatic nebulizers of the V-groove, Meinhard and cross-flow type have been the most widely used sample insertion devices for aerosol generation. The interaction geometry between the gas and liquid sample streams allows pneumatic nebulizers to be classified into two major groups, namely (a) pneumatic concentric nebulizers, which involve concentric interaction and (b) cross-flow nebulizers, which involve perpendicular interaction between the liquid and gas streams. Pneumatic nebulizers are well established and widely used on account of their simplicity, robustness, ease of use and low cost however, they provide low transport efficiency and tend to be clogged by high salt-content solutions [4]. 

Although the results indicate a good ionization stability, the problem of the unwanted formation of relatively large droplets could not be completely solved. This is likely due to the injection geometry since liquid is injected from one side, a liquid film occurs at one side of the nebulization channel. Further optimization of the injection geometry, such that the liquid is enclosed by the nebulization gas at both sides, might reduce this unwanted effect. 

Detector MS, JEOL JMS-SX102A reversed geometry (BE), accelerating voltage +5 kV, air pressure chemical ionization APCI, nebulizer 290°, ion source chamber 400°, discharge electrode, skimmer 1 aperture 300 pm, skimmer 2 aperture 400 pm, no nebulizer gas... 

The setup for atmospheric pressure photoionization (APPI) (Bos et ah, 2006 Hanold et ah, 2004 Raffaelli and Saba, 2003 Robb et ah, 2000) is very similar to that of APCI (Fig. 8.7). Only the corona discharge is replaced by a gas discharge lamp (krypton,10.0 eV) that generates ultraviolet (UV) photons in vacuum. The liquid phase is also vaporized by a pneumatic nebulizer and different geometries are used. Most analytes have ionization potentials below 10 eV, while high-pressure liquid chromatography (HPLC) solvents have higher ionization potentials (water 12.6 eV, methanol 10.8 eV, and acetonitrile 12.2 eV). 

In order to obtain maximum power of detection. the atomization efficiency should be as high as possible. Optimization of the geometry of the spray chamber and the nebulizer gas flow is required. The primary radiation should be well isolated by the monochromator and the amount of nonabsorbed radiation reaching the detector should be minimized by selection of the appropriate observation zone with the aid of a suitable illumination system. 

Optimization. For the optimization of ICP-MS with respect to maximum power of detection. minimal spectral interference, signal enhancement or depression, and maximum precision, the most important parameters are the power of the ICP, its gas flows (especially the nebulizer gas), the burner geometry, the position of the sampler, and the ion optical parameters. These parameters determine the ion yield and the transmission, and thus the intensities of analyte and interferenee signals. At increasing nebulizer gas flow, the droplet size decreases (Section 21.4.1) and thus the analyte introduction efficiency goes up, but at the expense of the residence time in the plasma, the plasma temperature, and the ionization [304]. However, changes of the nebulizer gas flow also... 

Isotopic analysis in cosmochemistry has further profited immensely from instrumental improvements that were developed over the last decade, including new skimmer cone geometries, improved desolvation nebulizer systems, and the use of higher capacity vacuum pumps for the expansion chamber. These... 

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