Carbon disulfide desorption efficiency

Johansen, I., Wendelboe, J. F. Dimethylformamide and Carbon Disulfide Desorption Efficiencies for Organic Vapors on Gas-Sampling Charcoal Tube Analysis with a Gas Chromatographic Backflush Technique, J. Chromatogr. 217, 317 (1981)... 

DESORPTION EFFICIENCY OF AROMATIC COMPOUNDS Sorbent Coconut Base Carbon 0.5 grams Solvent Carbon Disulfide 5 mL... 

For the study of desorption efficiency, or recovery, of vinyl acetate from the charcoal, known amounts of vinyl acetate, either neat or in solution in cyclohexane, were metered onto 100-mg beds of charcoal. The samples were desorbed with 1 mL of carbon disulfide after 1, 5, or 15 days storage at room temperature. The resulting solutions were analyzed by gas chromatography to determine the amount of vinyl acetate that was desorbed. The desorption efficiencies were then calculated according to the following equation ... 

The desorbing solvent was changed to acetonitrile, a more polar solvent, and another desorption-efficiency study performed. The results are plotted in Figure 2. The desorption again showed a dependence upon the loading, although at the lower levels it was higher than when carbon disulfide was used. 

Figure 2. The relationship between desorption efficiency and loading of vinyl acetate on activated charcoal for different storage periods. The 100-mg beds of charcoal were desorbed with 1.00 mL of (------) carbon disulfide or (---) aceto-...

Removal of the collected sample from the charcoal tube is accomplished by desorption with carbon disulfide or other solvents appropriate for a desirable desorption efficiency. The capped charcoal tube is scored with a file at both ends and the... 

Other corrections that must be considered are the collection efficiency of the charcoal tube and the desorption efficiency of carbon disulfide for this specific solvent. TABLE 1 lists the recommended collection tube for each solvent, flow rate to be used in samplings, and desorption efficiency of many organic compounds. (6) The desorption efficiency of carbon disulfide with the charcoal tubes can be determined by injecting a known amount of solvent onto the charcoal. At least five charcoal tubes are sampled and the 100 mg portion removed and placed in a septum sealed vial. A concentration applicable to the threshold limit value of the organic solvent in question is injected onto the 100 mg of charcoal by piercing the septum cap with a microliter syringe. Several concentrations of solvent should be checked to determine the variation in desorption efficiency with solvent concentration. In like manner, standards are prepared by adding the same amount of solvent to the carbon disulfide solution in the vial. The standards are analyzed with the samples. The percent desorption efficiency (D.E.) is determined as ... 

Samples collected on adsorbents can be desorbed by heat (thermal desorption) or by solvent extraction. Thermal desorption of samples from charcoal is not efficient however, because of the high temperature needed (950°C) to remove hydrocarbons from the charcoal (192). For this reason, most ACS passive headspace procedures use carbon disulfide to extract the adsorbed liquid residues. In 1967 Jennings and Nursten (193) reported concentrating analytes from a large volume of aqueous solution using activated charcoal as the adsorbent and extracting with carbon disulfide. Since then many adaptations of this method have been used to detect accelerants in fire debris, but currently dynamic headspace methods are seldom used because of the inconvenience of sampling and possible contamination issues with equipment. 

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