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Tools Available for Real-Time Exposure Assessment

Tools Available for Real-Time Exposure Assessment. Phil Smith, PhD, CIH CDR MSC, USN psmith@usuhs.mil. Objectives. Describe the range of field chemical detection systems now available

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Tools Available for Real-Time Exposure Assessment

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  1. Tools Available for Real-Time Exposure Assessment Phil Smith, PhD, CIH CDR MSC, USN psmith@usuhs.mil

  2. Objectives Describe the range of field chemical detection systems now available Describe trends in real-time detection and identification tools towards the ideals of “faster,” “cheaper,” and “easier-to-use”

  3. Types of Real-Time Exposure Assessment Tools Transportable Man-portable (Derived from Level 4) Increasing cost, expertise, complexity Handheld Quantitative Detectors Small Colorimetric Single-use Detectors

  4. Military Capabilities without Instrumentation M8 Paper (simple) M256 Kit (complicated)

  5. Length-of-Stain Indicator Tubes Color change produced through chemical rection Length of stain corresponds to concentration when a given volume of air is sampled

  6. Simple Handheld Instruments Capable of Quantitative Detection Photoionization detector as an example… A simple and rugged instrument that uses relatively little power Relies on atmospheric pressure photoionization of target analytes Selectivity is based on ionization potential

  7. Combined PID/Electrochemical Sensors Electrochemical Sensors

  8. Basis for Photoionization • UV light energy removes electron from neutral target molecules, creates ions • The resulting electrical current from these ions is proportional to contaminant concentration • The UV energy emitted must be sufficient to ionize that particular substance, or PID will not detect that analyte

  9. Current is measured and concentration is displayed on meter 100.0 ppm - + + + - - - + Gas enters the instrument Non-ionized gas exits the instrument intact Ions flow to charged Plates, producing current UV lamp PID Operation Courtesy of Bob Henderson, GFG Inc.

  10. What does a PID Measure? Some Ionization Potentials (IPs) for Common Chemicals 9.8 eV Lamp 10.6 eV Lamp 11.7 eV Lamp Not Ionizable by PID 15 14.01 14 Ionization Potential (eV) 13 12.1 11.47 12 11.32 10.66 11 10.5 10.1 9.99 10 9.54 9.24 9 8.4 8 IPA MEK Carbon Monoxide Styrene Benzene Oxygen Methylenechloride Ethylene Carbon Tet. Acetic Acid Vinyl Chloride Courtesy of Bob Henderson, GFG Inc.

  11. Sarin Detection and Cleardown, PID

  12. How does Ion Mobility Spectrometry work?

  13. How does Ion Mobility Spectrometry work?

  14. IMS analysis of VX Reactant Ion (H2O) Peaks SPME Fiber (with VX) Introduced Reduced Mobility (cm2V-1s-1)

  15. Person-Portable IR

  16. H | H | H | H | H | H | H – C – C – C – C – C – C – H | H | H | H | H | H | H n-hexane • When a molecular bond vibrates at the same frequency as IR light the bond and the light are resonant • The bond is “excited” as the IR light is absorbed by the molecule

  17. Field-Portable GC-MS

  18. Existing Level-1 and Level-2 Real-Time Information Capabilities • Detection systems found in Level-1 (single use • colorimetric) and Level-2 (handheld) have an important • role now in exposure assessment • New technologies (e.g., field-portable GC-MS) • will provide even better qualitative data for increased • clarity with immediate feedback • (2) Current systems provide actionable real-time data • to both hygienist (exposure assessment) AND workers • (safety); as systems are further refined for precision and • reliability this will grow in importance

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