Samples active charcoal

SP 6 Recommended operating procedure for the preparation of active charcoal samples... 

The ROPs include sampling, sample preparation, and analysis instructions for low-volume Tenax and XAD-2 air samples. Only the preparation of an XAD-2 low-volume air sample is presented in this article, while the thermal desorption of a Tenax tube is described in the context of gas chromatographic analysis see Chapter 10). Active charcoal is such a strong adsorbent that it requires more effective extraction methods than XAD-2 resin or Tenax tubes. Thus, the recoveries of CWC-related chemicals tend to be lower from active charcoal than from other air sampling materials. Furthermore, active charcoal is not usually used for the collection of organophosphorus chemicals. The sample preparation methods for active charcoal samples have not been validated in international round-robin or proficiency tests. 

Active charcoal sometimes is doped with various chemicals to modify its properties for a specific purpose. This may cause degradation of the sample chemicals and extraction problems. The matrix may also contain substantial amounts of water. For these reasons, the origin and background of active charcoal samples should always be ascertained. 

NIOSH Contract HSM-99-72-98, Scott Research Laboratories, Inc., Collaborative Testing of Activated Charcoal Sampling Tubes for Seven Organic Solvents, 1973. 

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. 

Fig. XVII-29. Nitrogen isotherms the volume adsorbed is plotted on an arbitrary scale. The upper scale shows pore radii corresponding to various relative pressures. Samples A, Oulton catalyst B, bone char number 452 C, activated charcoal F, Alumina catalyst F12 G, porous glass S, silica aerogel. (From Ref. 196).

Health and Safety. Remover formulas that are nonflammable may be used in any area that provides adequate ventilation. Most manufacturers recommend a use environment of 50—100 parts per million (ppm) time weighted average (TWA). The environment can be monitored with passive detection badges or by active air sampling and charcoal absorption tube analysis. The vapor of methylene chloride produces hydrogen chloride and phosgene gas when burned. Methylene chloride-type removers should not be used in the presence of an open flame or other heat sources such as kerosene heaters (8). 

Health and Safety. Petroleum and oxygenate formulas are either flammable or combustible. Flammables must be used in facUities that meet requirements for ha2ardous locations. Soak tanks and other equipment used in the removing process must meet Occupational Safety and Health Administration (OSHA) standards for use with flammable Hquids. Adequate ventilation that meets the exposure level for the major ingredient must be attained. The work environment can be monitored by active air sampling and analysis of charcoal tubes. 

Charcoal Tubes Reference has been made earlier to adsorption, which is the property of some solid materials, such as activated charcoal, to physically retain solvent vapors on their surfaces. In environmental health testing, the adsorbed vapors are removed, generally with a solvent, in a laboratory. The solvent is then analyzed by physical methods (gas chromatography, etc.) to determine the individual compounds whose vapors, such as benzene, were present in the sampled air. Industrial atmospheric samples can be collected in small glass tubes (4 mm ID) packed with two sections of activated charcoal, separated and retained with fiberglass plugs. To obtain an air sample, the sealed ends of the tube are broken off, and air is drawn through the charcoal at the rate of 1 liter per minute by means... 

Sorbent tubes Small glass tubes that contain sampling media such as silica gel or activated charcoal. 

Air samples can be analyzed by passing a known volume of air through a Teflon filter to catch air particulates followed by an activated charcoal filter to trap any gas-phase materials. The Teflon filters are extracted with hexane, concentrated, and analyzed by GC/MS. The charcoal traps are desorbed with carbon disulfide, concentrated, and analyzed by GC/MS. No performance data were reported (Dannecker et al. 1990). 

Activated Charcoal Method ACC charcoals 5g, flow rate 5 /min, sampled temp.s -73°C, sampling time lhr.,transfered into ionization chamber... 

In order to assess the accuracy of the present method, we compared it with two other methods. One was the Track Etch detector manufactured by the Terradex Corp. (type SF). Simultaneous measurements with our detectors and the Terradex detectors in 207 locations were made over 10 months. The correlation coefficient between radon concentrations derived from these methods was 0.875, but the mean value by the Terradex method was about twice that by our detectors. The other method used was the passive integrated detector using activated charcoal which is in a canister (Iwata, 1986). After 24 hour exposure, the amount of radon absorbed in the charcoal was measured with Nal (Tl) scintillation counter. The method was calibrated with the grab sampling method using activated charcoal in the coolant and cross-calibrated with other methods. Measurements for comparison with the bare track detector were made in 57 indoor locations. The correlation coefficient between the results by the two methods was 0.323. In the case of comparisons in five locations where frequent measurements with the charcoal method were made or where the radon concentration was approximately constant, the correlation coefficient was 0.996 and mean value by the charcoal method was higher by only 12% than that by the present method. 

The clean laboratory for trace metals was divided into three areas entrance laboratory (with clothes changing annex), instrument laboratory, and ultraclean sample preparation laboratory, all under positive pressure with active charcoal filtered air. Personnel using the clean rooms were required to wear hair caps, polyethylene gloves, laboratory coats, and designated shoes. These items are worn only in the clean rooms. 

A 10 g sample is roasted at 650°C and decomposed with hydrochloric acid/hydrogen peroxide. The Pt and Pd in the solution is pre-concentrated using adsorbent materials which are composed of active charcoal and anion resin. The adsorbent materials are washed sequentially with 2% ammonium bifluoride, 5% hydrochloric acid and distilled water, and subsequently ashed in a muffle furnace at 650°C. The total residue of ca. 0.25 mg is dissolved with 2 ml fresh aqua regia, then diluted to 5ml using 10% hydrochloric solution, and determined using ICP-MS, which has a detection limit of 0.2 ppb for Pt and Pd. The residue can also be mixed with a spectral buffer, and determined by DC-arc ES, which has detection limits of 0.3 ppb for Pt and 0.2 ppb for Pd. 

Diagnosis Be suspicious if an aerosol attack occurs in the form of yellow rain with droplets of yellow fluid contaminating clothing and the environment. Confirmation requires testing of blood, tissue and environmental samples. As for treatment, there is no specific antidote however, super-activated charcoal should be given orally if the toxin is swallowed. The only defense is to wear a protective mask and clothing during an attack. No specific immunotherapy or chemotherapy is available for use in the field. 

Various sample enrichment techniques are used to isolate volatile organic compounds from mammalian secretions and excretions. The dynamic headspace stripping of volatiles from collected material with purified inert gas and trapping of the volatile compounds on a porous polymer as described by Novotny [3], have been adapted by other workers to concentrate volatiles from various mammalian secretions [4-6]. It is risky to use activated charcoal as an adsorbent in the traps that are used in these methods because of the selective adsorption of compounds with different polarities and molecular sizes on different types of activated charcoal. Due to the high catalytic activity of activated charcoal, thermal conversion can occur if thermal desorption is used to recover the trapped material from such a trap. 

The width of the EPR absorption line is also dependent on the temperature of formation of the carbon and depends somewhat on whether the sample is carbonized in air or in vacuo as illustrated in Fig. 34. The difference in width obtained between air and in vacuo carbonization is a manifestation of the oxygen effect. If oxygen is added to coals and sugars heated above 500° or activated charcoals heated to a temperature above 100° a pronounced increase in width of the EPR signal occurs. The total, integrated intensity of the EPR absorption, however, does not change greatly. Thus, in this effect the total number of radicals remains approxi-... 

ASTM. 1987a. Standard practice for sampling atmospheres to collect organic compound vapors (activated charcoal tube adsorption method) - method D 3686-84. In 1987 annual book of ASTM standards. Vol. 11.03. Atmospheric analysis occupational health and safety. Philadelphia, PA American Society for Testing and Materials, 326-336. 

Adsorption experiments are carried out as follows. The solid sample (for example, activated charcoal) is shaken in contact with a solution with a known concentration of acetic acid. After equilibrium is reached (after 24 h), the amount of acetic acid adsorbed is determined. 

The limit of detection by Raman spectroscopy was 3-5 weight % for the oxime ester and methacrylonitrile for these samples. The shorter time required to reduce background fluorescence in those samples filtered through activated charcoal indicates that more careful sample preparation and purification would lower this limit. 

Surface Area and Mesh Size. 20/40 mesh sorbent is generally used to minimize the pressure drop across a sorbent tube. Some sorbents, such as Tenax-GC, are not available in these mesh sizes, but can still be used by increasing the cross-sectional area of the sampling tube to lower the overall pressure drop for these smaller sorbent particles. Surface areas vary from very low in Tenax-GC to over 1000 m2/g in activated charcoal. In some cases, the greater surface area may increase the capacity of the sorbent. 

The report (5) on the study recommended that a less active charcoal be tested. A literature survey did not yield any conclusive evidence for successful collection by recovery from alternative sorbents. On the basis of the little information available, we selected petroleum charcoal and three porous polymers to test (petroleum charcoal is less active than coconut charcoal). All the porous polymers were based on aromatic monomers, and they should be good collectors for nonpolar aromatics. Aliquots of 113 pg diphenyl were spiked onto these sorbents, and the samples were desorbed with various solvents. The results are given below. 

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