Charcoal, vapor trapping

Surveys for airborne activity are required for laboratories where radioiodine is used. The surveys should cover working areas and fume hood duct discharges. Check the efficiency of vapor entrainment at the fume hood face by collecting air samples from the operator s breathing zone using an activated charcoal sampling trap. Your radiation safety office can assist you or perform this service. 

Procedures for trapping accelerant vapors in the headspace of a closed container on charcoal that is either encased in a porous pouch or impregnated into a flexible membrane have been described (124). Trace amounts of explosive compounds can be trapped from hplc effluents onto a porous polymer microcolumn for confirmatory gc examination (125). 

The most common methods for trapping pesticide vapors from air use adsorbents. Common air sampling adsorbents include charcoal (derived from petroleum or coconut) and synthetic polymeric materials, such as cross-linked polystyrene and open-cell polyurethane foam. Charcoal has been used for the cumulative sampling of volatile... 

Many of the charcoal tube methods are based on NIOSH Method P CAM 127 (4) for organic solvents. In this method, a known volume of air is drawn through a charcoal tube to trap organic vapors, the charcoal is transferred to a vial, and the sample is desorbed with carbon disulfide. The sample is analyzed by gas chromatography (GC) with flame ionization detection (FID). Most methods use CS2 as the desorption solvent because it yields good recoveries from charcoal and produces a very low flame response. 

In this context, extraction means any process by which a fluid (air or water) comes into contact with a material to which the pollutant has an affinity. The affinity can be a physical trapping modified by some form of surface energy or a solvent extraction process based on enthalpic principles. The result is that the fluid is pumped through the sorption medium and the pollutant is reduced or eliminated from the fluid. Despite limitations, the most common sorption medium is activated charcoal — a form of charcoal treated with oxygen to open millions of tiny pores between the carbon atoms. It is amorphous and is characterized by high adsorptivity for many gases and vapors. 

An inert gas is bubbled through the sample. The volatile hydrocarbons are transferred into the vapor phase and trapped over a sorbent bed containing 2,6-diphenylene oxide polymer (Tenax GC). A methyl silicone (3% OV-1 on Chromosorb-W, 60/80 mesh) packing protects the trapping material from contamination. Other adsorbents such as Carbopack B and Carbosieve S III may also be used. If pentane and other low boiling hydrocarbons need to be detected, the sorbent trap should be filled with activated charcoal, silica gel, and Tenax, respectively, in equal amounts. 

It was assumed that all of the organic vapor(s) trapped on the charcoal were obtained during a 15 min. sampling interval. This highly unlikely assumption can be successfully utilized when it is suspected that the 8-hour TWA concentrations will be low. 

In 2006, Cnlcasi et al. (27A22) also reported on the free radical-related cytotoxicity of the vapor phase of MSS and the paradoxical temporary inhibition of cytotoxicity of vapor-phase free radicals by the MSS particulate phase. In their ESR stndies, the spin trap 5-(diethoxyphosphoryl)-5-methyl-l-pyrroline-iV-oxide (DEPMPO) was employed. They experimented with cigarettes made with cellulose acetate hl-ters, empty cavity hlters, and cavity hlters containing carbon (charcoal). In their stndy, hlters containing carbon were effective in redncing vapor-phase free radical formation, cytotoxicity, and lipid peroxidation in three cell lines. The... 

Nevertheless, cold traps are often the only satisfactory means of removing contaminants, although in ordinary e qrerimental work the charcoal trap is occasionally acceptable. A charcoal trap will remove oil and condensable vapors so that pressures to 10 tor or better may be secured, but it presents a serious restriction on pumping speed. 

The analysis of plasticizers in indoor air is most fiequently done using either adsorbent tubes (without a front filter) or sample trains. Sample trains corrsist of a filter followed by an adsorbent. They are interrded to separate particles botmd fiom gaseotrs plasticizers. Filters are made either of qirartz or glass fiber. Adsorberrts to trap the vapor phase plasticizers may be XAD CIS extraction disks, polyrrrethane foarrr, - or charcoal." " ... 

A known volume of air is drawn through a charcoal tube to trap the organic vapors present. 

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