Selective volatilization

In the direct insertion technique, the sample (liquid or powder) is inserted into the plasma in a graphite, tantalum, or tungsten probe. If the sample is a liquid, the probe is raised to a location just below the bottom of the plasma, until it is dry. Then the probe is moved upward into the plasma. Emission intensities must be measured with time resolution because the signal is transient and its time dependence is element dependent, due to selective volatilization of the sample. The intensity-time behavior depends on the sample, probe material, and the shape and location of the probe. The main limitations of this technique are a time-dependent background and sample heterogeneity-limited precision. Currently, no commercial instruments using direct sample insertion are available, although both manual and h ly automated systems have been described. ... 

Ross, R. T. and Gonzalez, J. G. "Direct Determination of Trace Quantities of Manganese In Blood and Serum Samples Using Selective Volatilization and Graphite Tube Reservoir Atomic Absorption Spectrophotometry". Bull. Environ. 

Ross, R. T., Gonzalez, J. G., and Segar, D. A. "The Direct Determination of Chromium In Urine by Selective Volatilization with Atom Reservoir Atomic Absorption". Anal. Chlm. Acta (1973), 63, 205-209. 

Chodola GR, Biswas N, Bewtra JK, et al. 1989. Fate of selected volatile organic substances in aqueous environment. Wat Pull Res J Can 24 119-142. 

Harkov R, Kebbekus B, Bozzelli JW, et al. 1984. Comparison of selected volatile organic compounds during the summer and winter at urban sites in New Jersey. Sci Total Environ 38 259-274. 

Wallace LA. 1986. Personal exposures, indoor and outdoor air concentrations and exhaled breath concentrations of selected volatile organic compounds measured for 600 residents of New Jersey, North Dakota, North Carolina, and California. Toxicol Environ Chem 12 215-236. 

Pavlostathis, S.G. and Mathavan, G.N. Desorption kinetics of selected volatile organic compounds from field contaminated soils. Environ. Sci. TechnoL, 26(3) 532-538, 1992. 

Tancrede, M. V. and Y anagisawa, Y. An anal34ical method to detemrine Henry s law constant for selected volatile organic compounds at concentrations and temperatures corresponding to tap water nse, J. Air Waste Manage. Assoc., 40(12) 1658-1663, 1990. 

Bozzelli JW, Kebbekus BB. 1979. Analysis of selected volatile organic substances in ambient air. Report to New Jersey Department of Environmental Protection, Program on Environmental Cancer and Toxic Substances, by New Jersey Institute of Technology, Air Pollution Research Laboratory. 

No studies on the transformation or degradation of fuel oils in the atmosphere were located. However, volatile components of fuel oils such as benzene, toluene, xylenes, and PAHs may be expected to enter the atmosphere where they are subjected to degradation processes. Further information on the atmospheric degradation of selected volatile hydrocarbons are presented in the ATSDR toxicological profiles for these chemicals (ATSDR 1989, 1990a, 1991a, 1991b). 

TABLE 4.4 Concentrations of selected volatile compounds prior to malo-lactic fermentation in Cabernet Sauvignon and Tempranillo wines data from Hernandez-Orte... 

TABLE 10.34 Distribution and (Yields) of Nitro-PAH Isomers (a) Formed from the Gas-Phase Reactions of Selected Volatile and Semivolatile PAHs with OH Radicals and N03 Radicals (Each in the Presence of Oxides of Nitrogen), (b) Formed by Electrophilic Nitration, and (c) Present in Diesel Exhaust" ... 

Sulfation Roasting. Acid roasting technology (Fig. 2) relies on differences in the volatility of the tetravalent oxides of selenium and tellurium at roasting temperatures of 500—600°C to selectively volatilize selenium from slimes. Acid roasting uses sulfuric acid as the oxidant for the conversion of selenium/selenides and tellurium/tellurides to their respective tetravalent oxides. Typical oxidation reactions are as follow ... 

Table IV. Influence of 16-23 weeks of storage of soya containing bread improver PASTE and POWDER on differences (d) in relative decreases (%) of GC peak areas of selected volatile compounds of white bread (22)...

TaUe nL Radial Growth of A, flavus as a Percent of Control After Two Days in Contact with Some Selected Volatiles (Adapted from 79)... 

Table 10.2 presents a summary of odour qualities, odour thresholds in water, and concentrations of some selected volatile compounds, which are characteristic flavour impact compounds, owing to their typical flavour quality and their rather low odour thresholds. These compounds are not formed during fermentation but originate from the raw material and contribute significantly to the typical flavour of a fruit. The components summarised in Table 10.2 are important compounds in wine and different fruits and are discussed later. 

Table 10.2 Odour qirality and minimmn and maximum odoirr thresholds in water [11] (Christoph and Bauer-Christoph 2006, unpublished results) of selected volatile impact compounds of raw materials for distilled spirits ...

Importance of Selected Volatile Components to Natural Orange, Grapefruit, Tangerine, and Mandarin Flavors... 

Influence of Selected Volatile Components on Flavor of a Bland Orange Juice Drink... 

Colombo, A., Bortoli, M., Knoppel, H., Pecchio, E. andVissers, H. (1993) Adsorption of selected volatile organic compounds on a carpet, a wall coating,... 

N02 and selected volatile organic compounds at 32 shoe, stalls located near busy roadways in Seoul, Korea. Science of the Environment, 323, 99-105. 

The variability of environmental data must also be regarded as being dependent on space and/or time. As an example, the temporal variability is demonstrated for the occurrence of volatile chlorinated hydrocarbons in river water (Fig. 1 -5). The very different pattern for the time functions of the selected volatile chlorinated hydrocarbons at two sampling locations 40 km apart shows that the concentration fluctuations are quite random. 

Response Surface Methodology (RSM) was used to investigate the effects of temperature, pH and relative concentration on the quantity of selected volatiles produced from rhamnose and proline. These quantities were expressed as descriptive mathematical models, computed via regression analysis, in the form of the reaction condition variables. The prevalence and importance of variable interaction terms to the computed models was assessed. Interaction terms were not important for models of compounds such as 2,5-dimethyl-4-hydroxy-3(2H)-furanone which are formed and degraded through simple mechanistic pathways. The explaining power of mathematical models for compounds formed by more complex routes such as 2,3-dihydro-(lH)-pyrrolizines suffered when variable interaction terms were not included. 

A data base of area count response was prepared for 23 selected volatiles using Lotus 123 spreadsheet software. Regression analysis for model determination was done with SAS software. 

Table II. Effects of Changes in Reaction Conditions on the Quantity of Selected Volatiles (ppm)...

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