Plasma alkali metals

Choice of Atomization and Excitation Source Except for the alkali metals, detection limits when using an ICP are significantly better than those obtained with flame emission (Table 10.14). Plasmas also are subject to fewer spectral and chemical interferences. For these reasons a plasma emission source is usually the better choice. 

Rubidium metal is commeicially available in essentially two grades, 99 + % and 99.9 + %. The main impurities ate other alkali metals. Rubidium compounds are available in a variety of grades from 99% to 99.99 + %. Manufacturers and suppliers of mbidium metal and mbidium compounds usually supply a complete certificate of analysis upon request. Analyses of metal impurities in mbidium compounds are determined by atomic absorption or inductive coupled plasma spectroscopy (icp). Other metallic impurities, such as sodium and potassium, are determined by atomic absorption or emission spectrograph. For analysis, mbidium metal is converted to a compound such as mbidium chloride. 

In this Section we want to present one of the fingerprints of noble-metal cluster formation, that is the development of a well-defined absorption band in the visible or near UV spectrum which is called the surface plasma resonance (SPR) absorption. SPR is typical of s-type metals like noble and alkali metals and it is due to a collective excitation of the delocalized conduction electrons confined within the cluster volume [15]. The theory developed by G. Mie in 1908 [22], for spherical non-interacting nanoparticles of radius R embedded in a non-absorbing medium with dielectric constant s i (i.e. with a refractive index n = Sm ) gives the extinction cross-section a(o),R) in the dipolar approximation as ... 

Jackson SE, Gunther D (2003) The nature and sources of laser induced isotopic fractionation in laser ablation-multicollector-inductively coupled plasma-mass spectrometry. J Anal At Spectrom 18 205-212 Jiang S-J, Houk RS, Stevens MA (1988) Alleviation of overlap interferences for determination of potassium isotope ratios by Inductively-Coupled Plasma Mass Spectrometry. Anal Chem 60 1217-1220 Lam JWH, Horlick G (1990) A comparison of argon and mixed gas plasmas for inductively coupled plasma-mass spectrometry. Spectrochim Acta Part B 45 1313-1325 Langmuir I, Kingdon KH(1925) Thermionic effects caused by vapours of alkali metals. Phil Trans R Soc A107 61-79... 

In the previous example, we have calculated the plasma frequency for metallic Na from the free electron density N. In Table 4.1, the measnred cutoff wavelengths, Xp, for different alkali metals are listed together with their free electron densities. The relatively good agreement between the experimental values of Xp and those calculated from Equation (4.20), within the ideal metal model, should be noted. It can also be observed that the N values range from abont 10 to about 10 cm leading to... 

The FAB plasma provides conditions that allow to ionize molecules by either loss or addition of an electron to form positive molecular ions, M" , [52,89] or negative molecular ions, M, respectively. Alternatively, protonation or deprotonation may result in [Mh-H]" or [M-H] quasimolecular ions. Their occurrence is determined by the respective basicity or acidity of analyte and matrix. Cationization, preferably with alkali metal ions, is also frequently observed. Often, [Mh-H]" ions are accompanied by [MH-Na]" and [Mh-K]" ions as already noted with FD-MS (Chap. 8.5.7). Furthermore, it is not unusual to observe and [Mh-H]" ions in the same FAB spectmm. [52] In case of simple aromatic amines, for example, the peak intensity ratio M 7[Mh-H] increases as the ionization energy of the substrate decreases, whereas 4-substituted benzophenones show preferential formation of [Mh-H]" ions, regardless of the nature of the substituents. [90] It can be assumed that protonation is initiated when the benzophenone carbonyl groups form hydrogen bonds with the matrix. 

The alkali metals, with only one free electron per atom, have lower plasmon energies than those of divalent free-electron metals such as Mg and A1 because the plasma frequency decreases with decreasing electron density. Thus, surface plasmon energies for alkali metals are in or near the visible, whereas they are in the far ultraviolet for Mg, Al, and Pb. Surface plasmon energies of the divalent metals Ag, Au, and Cu are shifted toward and into the visible because of interband transitions (see Fig. 12.9d) this is also the cause of the large values of c" for Au and Cu. 

Atomic spectrometry methods based on the ICP allow the determination of almost every element. Important restrictions are given by the plasma gas and its impurities (Ar, other noble gases, N, O and to some instance halogens), by the typical solvent used for the liquid solutions (H, O) and by some physical restrictions such as insufficient ionization (F) or emission lines below or above the observable wavelengths (F, Cl, Br, for some instruments the alkali metals ) [ 8 ]. 

Polymeric fullerene materials can be obtained by many methods, for example by irradiation with electrons or ions, treatment in a plasma generator, doping with alkali metals [9,28,46], direct chemical synthesis [47], or mechanical milling [29]. Because of the small penetration depth of light fullerenes can only be photopolymerized as thin films, but bulk photopolymer can be obtained by polymerization in solution [48,49]. Diffraction studies show that photopolymers usually have a disordered fee structure. Although some ordered films have been... 

Klyucharev, A.N. and Janson, M.L. (1988). Elementary Processes in Alkali Metal Plasma (in Russian) (Energoizdat, Moscow). 

Plasma Formation in Alkali Metal Vapors by Quasi-Resonant Laser Excitation... 

Optical diagnostic techniques are convenient and popular for alkali metal plasmas, because the strong and well-understood emission lines and continua can be easily observed in the visible and near-visible region. 

The alkali metal ions are very important for the proper functioning of biological systems, such as nerves and muscles Na+ and K+ ions are present in all body cells and fluids. In human blood plasma the concentrations are... 

Matrix interferences are often associated with the sample introduction process. For example, pneumatic nebulization can be affected by the dissolved-solids content of the aqueous sample, which affects the uptake rate of the nebulizer and hence the sensitivity of the assay. Matrix effects in the plasma source typically involve the presence of easily ionizable elements (EIEs), e.g. alkali metals, within the plasma source. 

The concentrations of alkali metals and chlorine were determined directly for the fuel samples using a inductively coupled plasma-atomic emission spectrometry apparatus in order to analyse sodium and potassium contents. Chlorine content was determined by Eschka method according to ASTM D2361-66. The concentrations are given on dry basis (table 1). 

An alkali metal bead, usually rubidium sulfate, is positioned above the jet in NPD, as seen in Fig. 2, and the current is applied to this bead, which causes it to achieve temperatures up to 800°C. The addition of hydrogen and air generates plasma around the bead, and carrier gas containing the solutes is delivered to the tip of the jet and the plasma. Specific ions are produced in the plasma from nitrogen- or phosphorus-containing compounds. These ions move to the charged collector. This movement of ions generates a current that is measured... 

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