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Detector Tubes for Chemical Warfare Agents (CWAs) PowerPoint Presentation
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Detector Tubes for Chemical Warfare Agents (CWAs)

Detector Tubes for Chemical Warfare Agents (CWAs)

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Detector Tubes for Chemical Warfare Agents (CWAs)

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  1. Detector TubesforChemical Warfare Agents (CWAs) Presented by: Gretchen B. Manning Product Group ManagerPortable Instruments © MSA 2002

  2. Federal help (analytical-grade equipment) is ~6 hours away First responders – typically local FD or Hazmat crew – are in charge at the beginning Need to (1) assess nature of threat (2) define “hot zone” (3) aid the injured Response to CWA Incident

  3. Chemical Weapons for Terrorists Nerve agents (G) GA (Tabun) IDLH = 0.03ppm (0.2mg/m3) GB (Sarin) IDLH = 0.03ppm (0.2mg/m3) GD (Soman) IDLH = 0.008ppm (0.07mg/m3) VX IDLH = 0.002ppm (0.02mg/m3) Blister agents (H) HD (Mustard) IDLH = 0.0004ppm (0.003mg/m3) Choking/Blood agents AC (cyanide) IDLH = 50ppm (60mg/m3) CK (cyanogen chloride) Phosgene IDLH = 2ppm (10mg/m3) TICs (easier to access) Ammonia IDLH = 300ppm (230mg/m3) Chlorine IDLH = 10ppm (30mg/m3)

  4. First Responder Detector Needs Fits the budgets of local fire companies Easy to use – first responders are not Ph.D. analytical chemists Extremely low rate of false positives, false negatives Some idea of nature of hazard

  5. Technologies for CWA Detection Ion Mobility Spectrometry (IMS) Portable Distinguishes among agent families Detects at IDLH/10 $6 -12K Pesky radioactive source Sensitive to some “battlefield interferents”

  6. Technologies for CWA Detection Chromatography (GC-MS, GC-IMS, etc.) Transportable (often in dedicated truck) Best variants detect at below TWA $25 -100K Skilled operators with “refresher training” Nearly no false positives/negatives Analyses require 30 minutes or more

  7. Portable Detects at IDLH/10 to IDLH Discriminates among families of agents $10/tube Simple to use…go / no-go Low false positive rate Technologies for CWA Detection Detector Tubes

  8. Based on color change when analyte participates in a chemical or enzyme-catalyzed reaction Indicator compound supported on solid(i.e. silica gel) inside a glass tube First implementation in the 1910s for carbon monoxide detection Over 300 target analytes, including CWAs and TICs What are Detector Tubes?

  9. reagent ampoule indication layer Example of Detector Tube Use (H) Detector tube for HD HN Components Chemically treated indication layer Reagent ampoule Pump to drawsample throughthe tube

  10. indication layer reagent ampoule Example of Detector Tube Use (H) Break off tube tips on both ends Attach to pump – 40 strokes (4-10 sec. ea.) Break reagent ampoule to wet indication layer White to blue color change indicates presence of agent 0.01mg/L 0.001mg/L

  11. mustard agent Indicator (colorless) developer (reagent) complex (blue) Detector Tube Chemistry (H) Mustard Agent

  12. How does nerve agent really work? Humans and detector tubes have more in common than you think!

  13. How does nerve agent work? • The synapse is the electrical switching center throughout the nervous system • Stimulating signals are fired across the synapses by chemicals Synapse • A chemical called acetylcholine carries the stimulating signals • An enzyme known as Cholinesterase, specifically acetylcholinesterase, breaks down or inhibits the stimulating signals • Pesticides and nerve agents actually inhibit the Cholinesterase, therefore, preventing the breakdown of the stimulating signal (acetylcholine) • The result jams the nervous system so muscles being directed by nerves to move can’t stop and move uncontrollably! Close up viewof synapse • Rapid twitching, paralyzed breathing, convulsions, and even death can occur

  14. Build-up of Cholinesterase inhibitors or nerve agent occurs Cholinesterase inhibition Constant firing of electrical messages Twitching, trembling, paralyzed breathing, convulsions, andeven death In summary…

  15. So, how does the human nervoussystem relate to detector tubes? Detector tubes are based on the same inhibition of enzyme – the same mechanism that affects humans

  16. Example of Detector Tube Use (G) For detection of Phosphoric Esters: nerve agents GA, GB, GD, VX Based on inhibition of enzyme – the same mechanism that affects humans Two reagent ampoules and two supported solids

  17. reagent 1 enzyme substrate reagent 2 < 0.00005 mg/L > 0.0005 mg/L (no reaction = agent is present!) Example of Detector Tube Use (G) • Read after 2 minutes • Break off both tube tips • Break ampoule 1 to wet white (enzyme) layer • Draw sample through tube (30 strokes) • Break ampoule 2 to wet yellow (substrate) layer

  18. O X + + = (CH3)3NCH2CH2SCCH3 + H2O (CH3)3NCH2CH2SH + CH3COOH substrate (white layer) enzyme (catalyst) in yellow layer nerve agent stops the first reaction…no color change! + O2N - -S – S - -NO2 HOOC COOH X O = (CH3)3NCH2CH2S – S - -NO2 + S - - NO2 S = =N COOH COOH COOH Detector Tube Chemistry (G)

  19. Detector Tube Target Analytes nerve agents(GA, GB, GD, VX) blister agent (H), blister agent (L), blister agents (general, including H) phenol, phosphene, phosgene, SO2, SF6, vinyl chloride, toluene trichloroethane, ammonia, aromatics (benzene) formaldehyde, acetic acid, acetone …over 300in all! CO2, CS2, hexane, gasoline, mercury, MEK, NO2 chlorine, ethylene, ethanol, triethylamine, ethylmercaptan blood/choking agents (CG, DP, AC, CK)

  20. Summary Colorimetrictubes provide an inexpensive, accurate, simple-to-use alternative for detection of TICsand CWAs Improvements to detector tubes will make them even more convenientto use They are an ideal option for local first responders withsmall budgets