Cold vapor

Miscellaneous Atomization Methods A few elements may be atomized by a chemical reaction that produces a volatile product. Elements such as As, Se, Sb, Bi, Ge, Sn, Te, and Pb form volatile hydrides when reacted with NaBH4 in acid. An inert gas carries the volatile hydrides to either a flame or to a heated quartz observation tube situated in the optical path. Mercury is determined by the cold-vapor method in which it is reduced to elemental mercury with SnCb- The volatile Hg is carried by an inert gas to an unheated observation tube situated in the instrument s optical path. 

Atomic absorption spectroscopy is more suited to samples where the number of metals is small, because it is essentially a single-element technique. The conventional air—acetylene flame is used for most metals however, elements that form refractory compounds, eg, Al, Si, V, etc, require the hotter nitrous oxide—acetylene flame. The use of a graphite furnace provides detection limits much lower than either of the flames. A cold-vapor-generation technique combined with atomic absorption is considered the most suitable method for mercury analysis (34). 

Different TiN-, TiC-, and TiAlN-based single layer coatings on steel alloyed with Cr, Ni, Mn, and WC were prepared by use of the cold vapor deposition technique. The thickness of the coatings varied from 2.7 to 6.4 pm. 

Wet Flare and Dry Flare Sometimes relatively hot vapors carrying condensates may be separated from the dry cold vapors. They do not run as separate headers but either low-pressure or high-pressure flare headers may be associated with any one of them. Thus a wet flare header may be, in fact, the low-pressure header, and the dry flare header maybe the high-pressure flare, or vica-versa. 

Material stored at or below its atmospheric pressure boiling point has no superheat. Therefore there will be no initial flash of liquid to vapor in case of a leak. Vaporization will be controlled by the evaporation rate from the pool formed by the leak. This rate can be minimized by the design of the containment dike, for example, by minimizing the surface area of the liquid spilled into the dike area, or by using insulating concrete dike sides and floors. Because the spilled material is cold, vaporization from the pool will be further reduced. 

Someone suggested putting steam up the stack to disperse the cold vapor. This seemed a good idea and the suggestion was adopted (Figure 2-6). 

As the cold vapor flowed up the stack, it met condensate flowing down. The condensate froze and completely blocked the 8-in.-diameter stack. The tank was overpressured and ruptured. Fortunately, the rupture was a small one and the escaping ethylene did not ignite. It was dispersed with steam while the tank was emptied. 

At Delphi, the Pythia sat on a tripod above a cleft in the rocks and inhaled cold vapors emanating from inside the earth, which induced in her an ecstatic alteration of mind. In this altered state, she uttered mystical observations in the presence of the Delphi Prophet, who translated them into oracular pronouncements. 

For PHg, a variety of different filter methods have been applied, such as Teflon or quartz fiber filters. Before analysis, these filters undergo a wet chemical digestion usually followed by reduction-volatilization of the Hg to Hg(0) and analysis using cold vapor atomic absorbance spectrometry (CVAAS) or cold vapor atomic fluorescence spectrometry (CVAFS). Recently, a collection device based on small qrrartz... 

Bloom NS, Fitzgerald WF. 1988. Determination of volatile mercury species at the picogram level by low temperature gas chromatography with cold-vapor atomic fluorescence detection. Anal Chim Acta 208 151-161. 

DeWild JF, Olson ML, Olund SD. 2002. Determination of methyl mercury by aqueous phase ethylation, followed by gas chromatographic separation with cold vapor atomic fluorescence detection, U.S. Geological Survey Open File Report 01 45, 23 p. 

USEPA] US Environmental Protection Agency. 1996. Method 1631 mercury in water by oxidation, purge and trap, and cold vapor atomic fluorescence (C VAFS). Draft method EPA 821-R-96-012. 

The technique that has been widely apphed for analyzing total merctrry in aqttatic biota since the late 1960s (cold vapor atomic absorption spectrophotometry) lemains a vahd analytical method. Accordingly, we irtfer that most of the historical data for total merctrry in fish tissues are vahd. Moreover, the historical data on total merctrry concentrations in fish tissues provide defettsible estimates of prior MeHg concentrations. 

No preconcentration or isolation/separation procedures applied Physico-chemical separation/preconcentration Hydride generation, cold vapor generation (Hg)... 

Techniques for analysis of different mercury species in biological samples and abiotic materials include atomic absorption, cold vapor atomic fluorescence spectrometry, gas-liquid chromatography with electron capture detection, and inductively coupled plasma mass spectrometry (Lansens etal. 1991 Schintu etal. 1992 Porcella etal. 1995). Methylmercury concentrations in marine biological tissues are detected at concentrations as low as 10 pg Hg/kg tissue using graphite furnace sample preparation techniques and atomic absorption spectrometry (Schintu et al. 1992). 

Certain volatile elements must be analyzed by special analytical procedures as irreproducible losses may occur during sample preparation and atomization. Arsenic, antimony, selenium, and tellurium are determined via the generation of their covalent hydrides by reaction with sodium borohydride. The resulting volatile hydrides are trapped in a liquid nitrogen trap and then passed into an electrically heated silica tube. This tube thermally decomposes these compounds into atoms that can be quantified by AAS. Mercury is determined via the cold-vapor... 

Element Flame AA Graphite Furnace AA ICP Cold Vapor Hg Hydride... 

Cold vapor mercury Light absorbed by atoms of mercury generated by chemical reaction at room temperature is measured An excellent technique for mercury analysis... 

Why is the cold vapor mercury technique good only for mercury ... 

Compare atomic absorption (both flame and graphite furnace), ICP, flame photometry, cold vapor mercury, hydride generation, atomic fluorescence, and spark emission in terms of ... 

ICP, cold vapor mercury, and hydride generation in regard to applicability and detection limit. 

R02019 Method 1631, Revision E Mercury in Water by Oxidation, Purge and Trap, and Cold Vapor Atomic Eluorescence Spectrometry 821R96013 Method 1632 Determination of Inorganic Arsenic in Water by Hydride Generation Elame Atomic Absorption... 

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