Semivolatile

Dynamic headspace GC/MS. The distillation of volatile and semivolatile compounds into a continuously flowing stream of carrier gas and into a device for trapping sample components. Contents of the trap are then introduced onto a gas chromatographic column. This is followed by mass spectrometric analysis of compounds eluting from the gas chromatograph. 

Semivolatile Organics Sampling EPA Method 0010 as contained in Test Methods for Evaluating Solid Waste, 3d ed., Report No. 

SW-846, is used to measure emissions of semivolatile principal organic constituents. Method 0010 is designed to determine destruction and removal efficiency (DRE) of POHCs from incineration systems. The method involves a modification of the EPA Method 5 sampling train and may be used to determine particulate emission rates from stationary sources. The method is applied to semivolatile compounds, including polychlorinated biphenyls (PCBs), chlorinated dibenzodioxins and dibenzofurans, polycyclic organic matter, and other semivolatile organic compounds. 

Gaseous and particulate pollutants are withdrawn isoldnetically from an emission source and collected in a multicomponent sampling train. Principal components of the train include a high-efficiency glass- or quartz-fiber filter and a packed bed of porous polymeric adsorbent resin (typically XAD-2 or polyurethane foam for PCBs). The filter is used to collect organic-laden particulate materials and the porous polymeric resin to adsorb semivolatile organic species (com-... 

SEMIVOLATILE HALOGENATED SUBSTANCES IN DRINKING WATER AFTER CHLORINATION. FACTORS AFFECTING THE COMPOSITION AND CONTENTS OF THESE BY-PRODUCTS... 

Prepai ative isolation of nonvolatile and semivolatile organic compounds fractions (hydrophobic weak acids, hydrophobic weak bases, hydrophobic neutrals, humic and fulvic acids) from natural and drinking waters in optimal conditions was systematically investigated by solid-phase extraction method with porous polymer sorbents followed by isolation from general concentrate of antropogenic and/or toxic semivolatile compounds produced in chlorination and ozonation processes. 

A second sampling program in Southern California sampled for polychlorinated dioxins and polychlorinated dibenzofurans at seven locations (9). Because of the semivolatile nature of these compounds, a tandem sampler was used with a glass fiber filter to collect the particulate-associated compo-... 

The principal PIC for penta and penta-treated wood would include volatile organic compounds (VOCs), semivolatile organic compounds (SVOCs), dioxins and furans, as well as SOj, COj, NO, and HCl. Penta would be expected to have undergone a very high destruction efficiency (DRE) during the fire (> 99.99%). Among the VOC emissions, the following chemicals likely contributed to air pollution problems benzene, bromobenzene, chloromethane, 1,3-butadiene, iodomethane, acetone, chloroform, and 1,2-dichloroethane. 

Cooling water - The cooling water, that provides cooling and moderation, also retains fission products - e.specially the chemically active semivolatiles, as demonstrated at the TMI-2 accident. 

A variation on the method of thermal modulation is the use of a length of eapillary eolumn eoated with a thiek film of stationary phase. At ambient oven temperatures, this results in a retention of semivolatile analytes, whieh may be subsequently released to the seeondary eolumn onee the trap is heated. The rapid eyeling time possible with this methodology has resulted in its eommon applieation as the intermediate trap in eomprehensive GC. 

Frequently, column problems are caused by the samples that are being analyzed. This type of problem is more likely to occur on capillary columns because of their low capacity for contamination. Contamination results when the sample contains nonvolatile or even semivolatile materials such as salts, sugars, proteins, and so on. Column contamination is more frequently observed with splitless injection because larger amounts of material are being injected on the column. 

The symptoms of column contamination include irregular peak shape, loss of resolution, loss of retention, irregular or noisy baseline, and ghost peaks from semivolatile materials of a previous run or from sample decomposition. Some of these problems can be the result of a contaminated injector. 

Conessa, J.A., FuUena, A., and Font, R., Tire pyrolysis Evolution of volatile and semivolatile compounds, Energy Fuel, 14, 409, 2000. 

Volatile and semivolatile compounds are present in honeys and are attributed to aroma qualities. Aroma compoimds can indicate floral and geographical origins and processing treatments. Aroma compounds come from nectar or honeydew. Aroma components can be also formed during fhermal processing and sforage (Bonvehi and Coll, 2003 Soria et ah, 2003). More than 400 components have been detected in the volatile flavor fraction of honey... 

In general, CE is simple, rapid, and low cost because it needs neither laborious treatment of the samples nor long times of analysis. However, its high detection limit is a major limitation of CE. CE is often poorly reproducible. Enzymatic assay is more suitable for quantifying one organic acid in honey samples because it is specific, precise, and accurate. GC is more suitable for analyzing volatile or semivolatile chemicals. HPLC is versatile and reproducible. However, common HPLC detectors such as UV-VIS are not very sensitive for organic aliphatic acids. 

Analytes Semivolatiles and slightly volatile compounds Volatiles and semivolatiles... 

There are basically three methods of liquid sampling in GC direct sampling, solid-phase extraction and liquid extraction. The traditional method of treating liquid samples prior to GC injection is liquid-liquid extraction (LLE), but several alternative methods, which reduce or eliminate the use of solvents, are preferred nowadays, such as static and dynamic headspace (DHS) for volatile compounds and supercritical fluid extraction (SFE) and solid-phase extraction (SPE) for semivolatiles. The method chosen depends on concentration and nature of the substances of interest that are present in the liquid. Direct sampling is used when the substances to be assayed are major components of the liquid. The other two extraction procedures are used when the pertinent solutes are present in very low concentration. Modem automated on-line SPE-GC-MS is configured either for at-column conditions or rapid large-volume injection (RLVI). 

Prime technique for thermally stable and semivolatile analytes (MW < 1200)... 

Suitable for semivolatile, relatively nonpolar and/or thermally labile analytes... 

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