Carbon disulfide desorption

Ai r Coconut shell carbon sorption, carbon disulfide desorption GC/FID 10 li g/sample No data NIOSH 1984... 

Ai r Charcoal sorption, carbon disulfide desorption GC/HSD No data No data ASTM 1987... 

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)... 

The effects of adsorption and desorption on the performance of fluidized beds are discussed elsewhere. Adsorption of carbon disulfide... 

The effects of adsorption and desorption on the performance of fluidized beds are discussed elsewhere. Adsorption of carbon disulfide vapors from air streams as great as 300 nr/s (540,000 ft3/min) in a 17-m- (53-ft-) diameter unit has been reported by Avery and Tracey ( The Application of Fluidized Beds of Activated Carbon to Recover Solvent from Air or Gas Streams, Tripartate Chemical Engineering Conference, Montreal, Sept. 24, 1968). 

Ai r Sorption by activated carbon, desorption by carbon disulfide GC/FID <20 mg/m No data Mackenzi e Peers 1985... 

Ai r Sorption by HBr-treated activated carbon, desorption with carbon disulfide GC/ECD 0.2 ppm No data LeFevre et al. 1989... 

Air Adsorption onto charcoal desorption with carbon disulfide GC/FID (OSHA Method 05) 0.11 ppm for 10 L sample 96 (8.5% RSD) OSHA 1979... 

Air Adsorption onto charcoal desorption with carbon disulfide, containing internal standard if desired GC/FID (NIOSH method 1003) 0.7 mg/m for 15 L sample 97 at 120-493 mg/m NIOSH 1994... 

OSHA. 1979. Method No. 05. Collection on charcoal adsorbent, desorption with carbon disulfide, analysis by gas chromatography using a flame ionization detector. Organic Methods Evaluation Branch, Occupational Safety and Health Administration Analytical Lab, Salt Lake City, UT. May 1979. 

We then designed model studies by adsorbing cinchonidine from CCU solution onto a polycrystalline platinum disk, and then rinsing the platinum surface with a solvent. The fate of the adsorbed cinchonidine was monitored by reflection-absorption infrared spectroscopy (RAIRS) that probes the adsorbed cinchonidine on the surface. By trying 54 different solvents, we are able to identify two broad trends (Figure 17) [66]. For the first trend, the cinchonidine initially adsorbed at the CCR-Pt interface is not easily removed by the second solvent such as cyclohexane, n-pentane, n-hexane, carbon tetrachloride, carbon disulfide, toluene, benzene, ethyl ether, chlorobenzene, and formamide. For the second trend, the initially established adsorption-desorption equilibrium at the CCR-Pt interface is obviously perturbed by flushing the system with another solvent such as dichloromethane, ethyl acetate, methanol, ethanol, and acetic acid. These trends can already explain the above-mentioned observations made by catalysis researchers, in the sense that the perturbation of initially established adsorption-desorption equilibrium is related to the nature of the solvent. 

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

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. 

For analysis, the monitor now serves as an analytical vessel for internal desorptions. The Elution Solvent, in most cases Carbon Disulfide, is added to the monitor. At this point, the procedure follows the NIOSH method P CAM 127. 

Analytical methods used are described by Bianchi et al. (1997). Methods 3M 3500 and 3M 3520 involve absorption onto a butadiene-specific activated charcoal, followed by desorption with carbon disulfide or with dichloromethane, respectively, and analysis by direct-injection gas chromatography with flame ionization detection. 

Sample preparation desorption with carbon disulfide... 

The NIOSH methods, in general, are based on adsorption of compounds in the air over a suitable adsorbent, desorption of the adsorbed analytes into a desorbing solvent, and, subsequently, their determination by GC using a suitable detector. A known volume of air is drawn through a cartridge containing coconut shell charcoal. The adsorbed compounds are desorbed into carbon disulfide, propanol, benzene, toluene, hexane, or methylene chloride. An aliquot of the solvent extract is then injected onto the GC column. FID is the most commonly used detector. Other detectors, such as ECD, ELCD, or PID have been used, however, in the method development of certain compounds. NIOSH method numbers and the analytical techniques are presented in Table 2.9.3. 

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-...

The collection tubes are prepared for analysis using distilled carbon disulfide as a desorbing agent. The desorption phase is usually complete within thirty minutes. The carbon disulfide solution is then analyzed by a Gas Chromatograph equipped with a flame ionization detector. The separation column specified by NIOSH is a 20 ft. x 1/8 in. stainless steel column packed with 10% FFAP on Chromosorb W. Alternative columns, such as 10% SE-30 on Chromosorb W or Porapak Q can be used depending on separation and peak resolving problems. 

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... 

All laboratory work with carbon disulfide should be performed in a hood because of its high toxicity. For complete desorption, the samples should be agitated or periodically shaken for a period of 30 minutes. If the desorbed sample is not analyzed immediately, it should be refrigerated, but no longer than two days. (7)... 

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 ... 

Air (occupational) Sample trapped on charcoal desorption with carbon disulfide GC/FID (NIOSH Methods 1500 and 1501) 10-100 ppb NR NIOSH 1984... 

Soil air Sample collection on activated charcoal desorption with carbon disulfide GC/FID NR 97-100 Colenutt and Davies 1980... 

Water Purge and trap on activated carbon desorption with carbon disulfide GC/FID conf. by GC/MS NR 96-99 Colenutt and Thorburn 1980... 

Thermal Desorption Thermal desorption is an alternative GC inlet system particularly used for VOC analysis. However, the analytes subjected to thermal desorption must be thermally stable to achieve successful analysis. Otherwise, decomposition occurs. This technique is mainly used for determination of volatiles in the air. Such a methodology requires sample collection onto sohd sorbents, then desorption of analytes and GC analysis. Traditionally, activated charcoal was used as a sorbent followed by extraction with carbon disulfide. However, solvent desorption involves re-dilution of the VOCs, thus partially negating the enrichment effect. Therefore, the sampling method is to pump a sample of gas (air) through the sorbent tube containing certain sorbents in order to concentrate the VOC. Afterwards, the sample tube is placed in thermal desorber oven and the analytes are released from the sorbent by application of high temperature and a flow of carrier gas. Additionally, desorbed compounds are refocused in a cold trap and then released into the GC column. Such a two-step thermal desorption process provides a narrow chromatographic band at the head of the column. 

The compounds absorbed are recovered either through extraction by means of solvents (often using carbon disulfide), or by thermal desorption in a carrier gas which avoids analyte dilution and the introduction of artefacts. 

UK/HSE. 1983. Carbon disulfide in air Laboratory method using charcoal adsorption tubes, solvent desorption and gas chromatography. London, England United Kingdom, Health and Safety Executive, Occupational Medicine and Hygiene Laboratory. MDHS Report No. 15. 

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