Sampling charcoal tube

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)... 

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. 

These compounds migrate rapidly to the back-up section of the charcoal tube. A 400 mg tube should be used for sample collection with a second 100 mg tube in series behind the large tube to determine breakthrough. 

Prepare a blank(s) during the sample period for each type of sample collected. For any given analysis, one blank will suffice for up to 20 samples collected. These blanks may include opened but unused charcoal tubes, and so forth. 

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... 

The shorter (backup, or second) section of the charcoal tube should be inserted into the sampling line so that the air is drawn through the longer section first. When analyzed, the backup section should be void of solvent vapors - in other words, there should have been no carry-over from the first section. 

H.W. Biermann and T. Barry, Evaluation of Charcoal Tube and SUMM A Canister Recoveries for Methyl Bromide Air Sampling, Report EH 9902, Cahfomia Environmental Protection Agency, Department of Pesticide Regulation, Sacramento, CA (1999). 

Occupational air (breathing zone) Collection on charcoal tubes DMF desorption dual column cap. GC/FID 0.5 g/sample (for 1-4 L sample) Not reported Hakkola and Saarinen 1996... 

Adsorb air sample onto charcoal tube extract sample and analyze... 

Occupational air Collection on charcoal tubes desorption with CS2 GC/FID 0.01 mg/ sample 12.5 Method 1003 NIOSH 1994... 

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. 

In some cases it was necessary to use a large charcoal tube, a low flow rate and a limited sample size to avoid losses due to breakthrough. 

In handling worldwide industrial hygiene problems for the Air Force, our Laboratory receives a heavy work load of charcoal tube and vapor monitor air samples. With our work load increasing, and more methods being applied to gas chromatography, any method which would remove some of the work load from our overworked gas chromatographs would be welcomed. 

Any alternate methods would have to have similar sensitivities, be relatively specific and able to analyze the samples quickly. We have found that infrared spectroscopy, when applied to hydrocarbon samples collected on charcoal tubes or vapor monitors, meets these requirements. 

Therefore, to check the possibility of using this IR procedure in our Laboratory, it was decided to evaluate the procedure against the recommended NIOSH GC procedures. We have limited our study to the hydrocarbons JP-4 aviation fuel and PD-680 cleaning solvent. In addition to evaluating the IR method for charcoal tubes and vapor monitors, we also compared the two methods on actual field samples. 

The charcoal tubes were broken open and the charcoal transferred into a stoppered glass test tube. One milliliter of carbon disulfide was pipetted into each tube, and 1.5 ml of carbon disulfide was pipetted into each 3M vapor monitor badge. After 30 minutes, aliquots of carbon disulfide were injected into the gas chromatograph and compared versus hydrocarbon standards prepared in carbon disulfide. The total areas of the sample and standard peaks were measured by the data system. 

Field Sampling. An opportunity arose where actual field samples could be analyzed by both the infrared and gas chromatographic methods. At Robins AFB, Georgia, workers were inspecting and repairing the interior and exterior of C-141 aircraft fuel tanks. They were exposed only to JP-4 fuel fumes. Duplicate charcoal tubes or vapor monitors were attached to each worker, one on each lapel. Samples were drawn through the charcoal tubes at 0.20 to 0.26 1pm by portable pumps attached to the worker s belt. Because of slight variations, the total volumes collected for the duplicates were close, but not exactly the same in all cases. Samples were then labeled and shipped to our Laboratory for analysis by both methods. 

Field Studies. As seen in Table VI, with the exception of three sets of duplicate charcoal tube samples, the results obtained with each method corresponded fairly well. The engineer in the field admitted that the duplicate 598, 602 and 610 could have been accidentally contaminated with some of the liquid aviation fuel. This could possibly explain the differing results by each method on these samples. It appears one set of samples was from workers exposed to low levels of JP-4 vapors, while the other set was from an area with very high concentrations. The variations in results on the low-level samples could be explained by several factors. Among these would... 

It appears there would be several advantages in using the proposed infrared method analyses could be performed much faster using the IR method. An IR scan takes 45 seconds versus -16 minutes by the NI0SH GC method. The IR method is adapted to charcoal tubes sampled by current recommended techniques. The majority of laboratories have infrared spectrometers and the simplest of models will do utilization of the IR method would relieve pressure of the heavily used gas chromatographs. The... 

We believe it has been shown that this method for infrared analysis of hydrocarbons collected on charcoal tubes and vapor monitors is a valid and acceptable one. Further work is being done to validate the method for other hydrocarbons such as petroleum naphtha, Stoddard solvent, and other JP aviation fuels. Additionally, work is being done to determine the 3M monitor sampling rate for JP-4. 

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. 

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