Field screening methods

Ion mobility spectrometry (IMS, Section 5.5) is the most common instrument used in tiie field detection of explosives. At airports, IMS is utili2fid to screen devices such as portable computers a swiped sample obtained by wiping a sample pad over the case is inserted into the instrument, producing an alarm-noalarm response. IMS can also be used in a laboratory as part of a GQMS or IMS-MS system, but to date its forensic applications have been outside the laboratory. IMS is also used at border crossings and ports to detect smu led drugs. 

Intense interest has arisen in developing microchip-based sensors and chemical noses to supplement IMS instrumentation and bomb-snifiing dogs. Because small quantities of analytes are involved, detection modes are usually, 

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Easterling et al. [161] has reported a rapid field screening method for the determination of elemental mercury in soil. This method involves thermal desorption of the mercury onto gold, followed by thermal desorption from the gold film mercury analyser. 

In answering these questions, we must keep in mind that field screening methods produce mostly semiquantitative data that are not acceptable for confirmation sampling or site closure and that the screening method detection limits may not be sufficiently low for comparisons to the action levels. 

Olivero, R. A. Cameron, R. E. Cabbie, K. J. Homsher, M. T. Stapanian, M. A. Brown, K. W., Environmental Field Sampling Expert System--Development of a Soil Sampling Advisor, In Proc. 1st Inti. Svmp, on Field Screening Methods for Hazardous Waste Site Investigations. Las Vegas, Nevada, 1988, pp 325-339. 

Provide a level of confidence for a select portion of preliminary data, focus on specific pollutants and specific levels of concentration quickly, by using field screening methods and verifying 10% by more rigorous analytical methods and quality assurance. 

EPA. 1988d. Determination of chlordane in soil by enzyme immunoassay. U.S. EPA, Res. Dev. EPA/600/D-89/189, Field Screening Methods Hazard. Waste Site Invest 433-437. 

Field Screening Methods Catalog. Washington, DC U. S. Environmental Protection Agency, 1988. TJ Kuehn, DA Bell. Field screening Methods for Hazardous Waste and Chemicals. Pittsburgh, PA Air and Waste Management Association, Vols 1 and 2, 1993. 

Liebman, S.A., Phillips,C.E., Fitzgerald, W., Levy, E.J. Proc. Third Intemat. Sympos. Field Screening Methods, EPA/EMSL, Las Vegas,... 

Environmental Applications Although ion-selective electrodes find use in environmental analysis, their application is not as widespread as in clinical analysis. Standard methods have been developed for the analysis of CN , F , NH3, and in water and wastewater. Except for F , however, other analytical methods are considered superior. By incorporating the ion-selective electrode into a flow cell, the continuous monitoring of wastewater streams and other flow systems is possible. Such applications are limited, however, by the electrode s response to the analyte s activity, rather than its concentration. Considerable interest has been shown in the development of biosensors for the field screening and monitoring of environmental samples for a number of priority pollutants. 

Today an increasing importance of qualitative analysis can be stated in certain fields. This is due to an increasing number of materials under study, especially active agents of interest on the one hand, and the many and diverse ways of synthesis (e.g., by combinatorial chemistry) on the other hand as well as the increasing demands on quality. Because analytical laboratories in research and routine control would be overtaxed in their capacity if full quantitative analyses were done generally, screening methods become more and more significant. 

IR-based TPH methods Laboratory and field screening—most appropriate for water and soil Primarily diesel and fnel oils Most hydrocarbons, with exception of volatile and very high hydrocarbons EPA Method 418.1... 

Immunoassay Field screening—most Varions products (but yields only Aromatic hydrocarbons EPA Method 4030... 

A number of procedures, based on microanalysis of samples for known physical properties (Chapter 8, 9, and 10), have also been employed. Eor example, field screening, which uses infrared spectroscopy, employing a portable version of the laboratory procedure has been used (Kasper et al., 1991). Eield turbido-metric methods favor the determination of high-boiling hydrocarbons and are... 

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