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Detector Tubes for Chemical Warfare Agents (CWAs) Presented by: Gretchen B. Manning Product Group Manager Portable Instruments © MSA 2002 www.msanet.com.

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Presentation on theme: "Detector Tubes for Chemical Warfare Agents (CWAs) Presented by: Gretchen B. Manning Product Group Manager Portable Instruments © MSA 2002 www.msanet.com."— Presentation transcript:

1 Detector Tubes for Chemical Warfare Agents (CWAs) Presented by: Gretchen B. Manning Product Group Manager Portable Instruments © MSA 2002

2 Response to CWA Incident 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

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

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 $ K Skilled operators with “refresher training” Nearly no false positives/negatives Analyses require 30 minutes or more

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

8 What are Detector Tubes? 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

9 Example of Detector Tube Use (H) Detector tube for HD HN Components Chemically treated indication layer Reagent ampoule Pump to draw sample through the tube indication layer reagent ampoule

10 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 indication layer reagent ampoule 0.01mg/L 0.001mg/L

11 Detector Tube Chemistry (H) mustard agent Indicator (colorless) developer (reagent) complex (blue) 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? Synapse Close up view of synapse  The synapse is the electrical switching center throughout the nervous system  Stimulating signals are fired across the synapses by chemicals  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!  Rapid twitching, paralyzed breathing, convulsions, and even death can occur

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

15 So, how does the human nervous system 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 Example of Detector Tube Use (G) √Read after 2 minutes < mg/L > mg/L (no reaction = agent is present!) reagent 1 reagent 2 substrate enzyme √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 Detector Tube Chemistry (G) (CH 3 ) 3 NCH 2 CH 2 SCCH 3 + H 2 O = O + (CH 3 ) 3 NCH 2 CH 2 SH + CH 3 COOH + substrate (white layer) enzyme (catalyst) in yellow layer + O 2 N - - S – S - - NO 2 HOOC COOH (CH 3 ) 3 NCH 2 CH 2 S – S - - NO 2 + COOH S - - NO 2 S = = N COOH = O nerve agent stops the first reaction…no color change! X X

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

20 Summary They are an ideal option for local first responders with small budgets Improvements to detector tubes will make them even more convenient to use Colorimetric tubes provide an inexpensive, accurate, simple-to-use alternative for detection of TICs and CWAs


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