Volatile organic compounds, passive

Begerow J, Jermann E, Keles T, et al. 1995. Passive sampling for volatile organic compounds VOCs in air at environmentally relevant concentration levels. Fresenius Journal of Analytical Chemistry 351(6) 549-554. 

Reclaim is a passive, in situ technology that uses a hydrophobic porous polymer to attract, adsorb, and concentrate petroleum hydrocarbons and volatile organic compounds (VOCs) from soils and/or groundwater. Reclaim is considered a passive treatment technology because it requires no mechanical equipment remediation consists of placing polymer-filled canisters in recovery wells and allowing the containers to attract and adsorb organic contaminants. Reclaim canisters are then recycled and contaminants recovered for analysis and/or disposal. This polymer extracts contaminants whether they are in liquid phase, vapor phase or dissolved phase in water. 

Cao, X.-L., and C. N. Hewitt, Build-up of Artifacts on Adsorbents during Storage and Its Effect on Passive Sampling and Gas Chromatography-Flame Ionization Detection of Low Concentrations of Volatile Organic Compounds in Air, . /. Chromatogr. A, 688, 368-374 (1994). 

Vroblesky, D.A. 2007. Passive diffusion samplers to monitor volatile organic compounds in groundwater. In R. Greenwood, G.A. Mills, and B. Vrana (eds), Passive Sampling Techniques in Environmental Monitoring, pp. 295-309. Amsterdam Elsevier. 

Cao XL, Hewitt CN. 1991. Evaluation of Tenax-GR adsorbent for the passive sampling of volatile organic compounds at low concentrations. Atmos Environ Part A 27A 1865-1872. 

Wallace, L.A., E.D. Pellizzari, T.D. Hartwell, R. Peritt and R. Ziegenfus (1987b). Exposures to benzene and other volatile organic compounds from active and passive smoking. Arch. Environ. Health, 42, 272-279. 

Brown V.M., Crump D.R. and Gardiner D. (1992) Measurement of volatile organic compounds in indoor air by a passive technique. Environ. Technol., 13, 367-375... 

Cohen M.A., Ryan P.B., Yanagisawa Y. and Hammond S. (1990) The validation of a passive sampler for indoor and outdoor concentrations of volatile organic compounds. J. Air and Waste Management, 40, 993-997. 

Chung, C-W., M. T. Morandi, T. H. Stock M. Afshar, 1999. Evaluation of a passive sampler for volatile organic compounds at ppb concentrations, varying temperatures, and humidities with 24-hr exposures. 2. Sampler performance. Environ. Sci. Technol. 33 3666-3671. 

The EPA (US Environmental Protection Agency) describes a process for sampling and analysis of volatile organic compounds (VOCs) in the atmosphere. It is based on the collection of air samples in passivated stainless steel canisters (SUMMA canisters). The organic components are separated by GC and determined using conventional GC detectors or by mass spectrometry (Figure 4.1). The use of mass spectrometers allows the direct positive detection of individual components (Madden, 1994). 

Passive samplers are widely used in monitoring volatile organic chemicals (VOCs) in groundwater. Such samplers have the potential to reduce costs of monitoring from the high levels associated with the use of pumps to sample the test wells. Moreover, the risk of loss of volatile analytes during sample transport and storage is substantially reduced once the compounds are accumulated in the sampler sorption phase. 

Organic solvents used in liquid membranes for both passive and facilitated transfer can be either nonpolar aliphatic or aromatic hydrocarbons such as toluene and kerosene, or polar organic compounds such as dihexylether. The polarity of the membrane liquid phase can be modified readily by the addition of small amounts of hydrophobic polar organic solvents (e.g., trioctyl phosphine oxide, dodecanol). Liquid membranes are generally more permeable than solid SP membranes thus allowing faster separation. They are also suitable for the separation of both volatile and nonvolatile analytes. 

Odorant molecules are typically small organic molecules with a molecular weight of 26-300. An odor consists of millions of volatile molecules emitted into the fluid media of air or water. The vapor pressure of a compound is a measure that directly relates to its volatility odorants with high vapor pressures in ambient conditions volatilize readily. Inanimate odor sources passively emit odors animate odor sources may passively or actively emit them. The intensity and chemical nature of both passive and active emission are a function of the properties of the compounds present, the temperature, and the atmospheric pressure. Examples of inanimate passive emission would include an inanimate object such as a glass of wine emitting hundreds of compounds from the fluid surface into the headspace in the immediately vicinity of the fluid." Animate passive emission often occurs as a function of a metabolic process. For example, the odors typically associated with rotting meat are produced and emitted by microbes as a byproduct of metabolism." Mammals emit CO2 and lactic acid as a byproduct of metabolism CO2 and lactic acid may be used by insects, such as mosquitos, to locate mammalian hosts." " In active emission, odors are synthesized and emitted by an animate signaler. Examples... 

Thermal desorption Volatile compounds in gases such as pollutants in air can be trapped in a small adsorption tube, either by pumping the gas through or by passive diffusion. The packing in the trap can be chosen from a wide variety of adsorbents (molecular sieves, graphitized carbon blacks, organic polymers). After sample collection the adsorption tube is rapidly heated in a stream of purge gas which transports the released analytes to the GC column where the separation runs. 

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