Passive activated carbon monitor

As part of the radon program at EML to develop or improve and field test radon monitors, a modified activated carbon device (Warner, 1986) was developed to obtain higher measurement sensitivity. As a result, we have surveyed 380 buildings in six states in the eastern United States. The purpose of the measurements reported in this paper was to test the feasibility of the new version of the passive activated carbon device and to obtain data on indoor radon levels in different geographical locations. 

The detector used to measure indoor radon was the latest version of the passive activated carbon device developed at EML (George, 1984 Warner, 1986), which consists of a thin-walled aluminum canister with a screen cover to expose 80 g of carbon to the test atmosphere. Although not as physically rugged as earlier models, properly packed this monitoring device was as successful in conducting the surveys through the mail. 

Passive diffnsion of accelerant vapors onto an adsorbent placed inside the container of fire debris has gained wide acceptance in the United States because it is nonlaborious and takes little time to perform. Dietz (182) has reported a procedure that uses activated carbon-coated Teflon strips, similar to devices used in enviromnental monitoring badges, to recover as little as 0.2 tiL of an equal mixture of gasoline, kerosene, and diesel fuel. Neuman (183) reported on the optimized method as well as the effects of time, temperature, strip size and sample concentration. The most recent recommended procedure heats the samples at approximately 60-80°C for 8-24 hs (184). The optimum adsorption time for maximum sensitivity will depend on the adsorption package, the sample itself, and the temperatures. The accelerants are desorbed with carbon disulfide, which can be concentrated to improve sensitivity and shows little response, but may cause a pressure disturbance to the FID. Another advantage to this technique is the fact that multiple analyses may be performed from one sample. The carbon strip can be easily cut into smaller pieces, placed into vials, and frozen for later analysis. 

The selectivity of immunosensors for steroid analytes is achieved with the use of appropriately selected monoclonal antibodies. The carbon working electrode provides a suitable surface for passive adsorption of proteins, and can therefore be tailored with an appropriate antibody, so that it will act as an immunoactive surface upon which an immunoaffinity assay can be performed an electrochemical signal can then be generated by monitoring the production of an electroactive species at the underlying electrode surface. We and other workers have found that to retain maximum monoclonal antibody activity, it is desirable to use a primary antibody (rabbit IgG), which serves both to capture (e.g., from a culture medium) and to orientate the mAb. Hence this approach... 

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