Plasma sources types

LC-MS interfaces generally produce ions with a relatively wide energy and spatial distribution. Table 7.49 lists the main LC-MS interface types. The most important types of contemporary LC-MS interfaces are direct inlet systems PB, TSP, API, ICPI and MIP (the latter two for plasma source detection, cf. Section 7.3.3.5). Three main types of LC-MS coupling systems are usually distinguished ... 

It was discovered early that the penetration of hydrogen from a plasma source into a substrate of p-type silicon is greatly reduced if the substrate is covered by a thin layer of strongly n-type material (Pankove et al., 1985 ... 

There are two popular types of plasma sources l) the direct current plasma (DCP), and 2) the inductively coupled plasma (ICP). In the commercial version of the former plasma source (marketed by Spectrometries, Inc.), the sample is aspirated with argon through a small orifice into a chamber where the large droplets settle out and the fine mist is conveyed by the argon stream through a chimney to the vertex of a plasma which is in the form of... 

In AAS, the excitation source inert gas emission offers a potential background spectral interference. The most common inert gases used in hollow cathode lamps are Ne and Ar. The data taken for this table and the other tables in this book on lamp spectra are from HCLs however, electrodeless discharge lamps emit very similar spectra. The emission spectra for Ne and Ar HCLs and close lines that must be resolved for accurate analytical results are provided in the following four tables. This information was obtained for HCLs and flame atom cells and should not be considered with respect to plasma sources. In the Type column, I indicates that the transition originates from an atomic species and II indicates a singly ionized species. 

Several other observations of a variety of doubly-charged negative ions have been made by different investigators using different experimental approaches. The experimental methods employed do, however, have some common bases. The experiments described below involve different ion sources, but these can be classified into two main categories conventional Nier-type ion sources and relatively cool plasma sources. The experiments of Ahnell and Koski Dougherty and Bowie and Stapleton involve the Nier-type ion sources. The experiments of Schnitzer and Anbar and Stapleton and Bowie like those of Baumann, Heinicke,... 

The above mechanisms for the formation of and S are plausible and explain the observation of 0 and S by Stuckey and Kiser and by Baumann, Heinicke, Kaiser and Bethge. They specifically involve excited states both of Z and of Z. And the lifetime of the Z would permit significant concentrations of Z to be formed in a plasma source, such as found in the omegatron or the Penning source. However, it is anticipated that only much lower concentrations of Z would be formed in the Nier-type ion source employed in most conventional mass spectrometers. It is unlikely, therefore, that the above mechanisms can satisfactorily account for the observation of F formed from CF3CI, as reported by Ahnell and Koski or the various Z species reported by Bowie and Stapleton ... 

Both flame and plasma sources are sensitive and selective techniques measuring as little as 10 16 g of analyte solution in complex mixtures. However, understanding the techniques and the type of sample being analysed helps in deciding which technique is suited for a particular application. 

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