Chemical vapor generation

A. Lopez-Molinero, O. Mendoza, A. Callizo, P. Chamorro and J. R. Castillo, Chemical vapor generation for sample introduction into inductively coupled plasma atomic emission spectroscopy vaporisation of antimony(III) with bromide. Analyst, 127(10), 2002, 1386-1391. 

M. Grotti, C. Lagomarsino and R. Frache, Multivariate study in chemical vapor generation for simultaneous determination of arsenic, antimony, bismuth, germanium, tin, selenium, tellurium and mercury by inductively coupled plasma optical emission spectrometry, J. Anal. At. Spectrom., 20(12), 2005, 1365-1373. 

Sturgeon, R.E., X. Guo, and Z. Mester. 2005. Chemical vapor generation Are further advances yet possible Anal. Bioanal. Chem. 382 881-883. 

Pohl, P. 2004. Recent advances in chemical vapor generation via reaction with sodium tetrahydroborate. 

D Ulivo, A. 2004. Chemical vapor generation by tetrahydroborate (III) and other borane complexes in aqueous media—A critical discussion of fundamental processes and mechanisms involved in reagent decomposition and hydride formation. Spectrochim. Acta B 59 793-825. 

Chemical vapor generation is another important variant of AAS suitable for the determination of several elements forming elemental vapors (Hg) or volatile hydrides (As, Se, Bi, Sn, Ge, Te, Pd). The cold vapor technique generating the volatile element is almost exclusive to Hg, although there is one report of Cd. There is a voluminous literature on the determination of Hg by atomic absorption of Hg atoms in the gaseous phase beginning from the early days after development and continuing presently. 

NaBHjCN (sodium cyanotrihydroborate), or electrochemical reduction to generate hydrides of As, Se, Bi, Sn, Sb, Ge, and Pb. These are then swept into either a flame directly or into a flame- or electrically heated tube for atomization. Atomization of the gaseous hydrides occurs in argon (or nitrogen)-hydrogen diffusion flame, electrically-heated quartz tube, flame-heated quartz tube (quartz tube atomizers QTA), flame-in-tube (FIT) atomizer or a graphite furnace. Other techniques of chemical vapor generation can be as chlorides, Ni carbonyl, tetramethyl lead or chelates. 

D Ulivo A, Loreti V, Onor M, Pitzalis E, and Zamboni R (2003) Chemical vapor generation atomic spectrometry using amineboranes and cyanotrihydroborate(III) reagents. Analytical Chemistry 75 2591-2600. 

CHEMICAL VAPOR GENERATION AAS 4.1. Properties and Sample Requirements... 

The two techniques for chemical vapor generation are different insofar as in CVAAS the chemical reaction generates already mercury atoms which only have to be volatilized and measured in an... 

Chemical vapor generators of very many different designs are described in the literature. They can be classified into batch and flow systems, and the latter can be continuous flow or FI systems. 

FIG. 6. Schematic design of a batch system for chemical vapor generation in the special configuration for cold vapor AAS with amalgamation (Courtesy of Perkin-Elmer). 

The specificity of the chemical vapor generation techniques for an inorganic, ionic form of the analyte can be used, if required, for speciation purposes. If conditions are chosen properly it may, for example, be possible to distinguish between the inorganic and organic constituents of an element in a sample. 

In the chemical vapor generation techniques, the analyte element passes into the atomizer as the gaseous hydride (HGAAS) or as the gaseous element (CVAAS), while concomitants normally remain in the reaction vessel. Consequently, due to the small number of components in the gas phase in the atomizer, spectral interferences can be virtually excluded. 

Vieira, M.A., Ribeiro, A.S., Dias, L.F., Curtius, A.J. (2005) Determination of Cd, Hg, Pb and Se in sediments slurries by isotopic dilution cahbration ICP-MS after chemical vapor generation using an on-line system or retention in an electrothermal vaporizer treated with iridium. Spectrochim. Acta Part B, 60, 643-652. 

A chemical vapor generation system consists of the vapor source and volume dilution through a mixing device. The controlled vapor from the vapor source is introduced into the dilution flow and mixing device to achieve the desired concentration. The process is very simple. Precise control of various flow blends and understanding pertinent basic physical chemical laws determine the suitabihty of a given dissemination technique. 

This SOP involves the operation of a multipurpose chemical vapor generation system for generating controlled toxic vapor concentrations over a wide range, in an approved hood or agent test chamber. This vapor generation system is primarily used for testing detection and alarm systems. 

The atomic absorption spectrometer contrAA 300 from Analytik Jena AG (Jena, Germany) is the first commercially available instrument for HR-CS AAS, and it is closely related to the DEMON research spectrometers described in detail in Section 3.2.2. At the time of writing this book, the instrument was available only for flame atomization and chemical vapor generation techniques (refer to Figure 3.15). However, the manufacturer has already announced that a combined flame and graphite furnace version will be introduced in the near future. 

Burgener, J. A. (1995) Parallel path induction pneumatic nebuUser. U.S. Patent 5,411,208. Feng, Y. L., Lam, J. W., and Sturgeon, R. E. (2001) Expanding the scope of chemical vapor generation for noble and transition metals. Analyst, 126,1833. ... 

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