AVS 50th International Symposium
    Homeland Security Topical Conference Wednesday Sessions
       Session HS-WeP

Paper HS-WeP4
Vapor Preconcentration during Explosive Detection: Study of Variables in a NIST Standard Test System

Wednesday, November 5, 2003, 11:00 am, Room Hall A-C

Session: Poster Session on Science & Technology for Homeland Security
Presenter: R.M. Verkouteren, National Institute of Standards and Technology
Correspondent: Click to Email
The reliable detection of ever-decreasing levels of explosives constantly challenges the public safety and analytical communities. The total absence of false negative responses is required while minimizing the rate of false positive responses. While much progress has been achieved, further significant improvements in methods may be enabled by the systematic study of the total measurement process, especially near the limits of detection. Fundamental data from such studies are needed by system designers, instrument manufacturers, and public safety officials in improving the sensitivity and specificity of portal screening systems, while balancing the human dimensions that include ease of use, speed of analysis, detection risk tolerance, personal invasiveness, and profiling decisions. Described will be a NIST standard test system and preliminary flash desorption experiments, designed to investigate variables affecting the efficiency of one segment of explosive detection: the preconcentration stage. The standard test system was built to enable robust monitoring and control over static and dynamic temperature regimes and gas flow, and was designed to allow modifications in the configuration of components. We intend that this system be used to compare reliably the relative performances of materials, configurations, and methods, and to provide a benchmarking reference to enable measured improvements to technology. In the NIST system, a known quantity of sample is introduced onto a metal felt collector, which is then desorbed into a gas stream by resistive heating and monitored by IR thermography. The vapors released are then trapped on a second metal felt collector, the temperature of which is controlled by a thermoelectric cooler. The amount of trapped sample is determined by off-line quantitative methods. Factorial experimental design will be discussed as an effective tool to investigate a large number of variables in a limited number of experimental runs.