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Detector Tubes for Chemical Warfare Agents (CWAs). Presented by: Gretchen B. Manning Product Group Manager Portable Instruments. © MSA 2002. Federal help (analytical-grade equipment) is ~6 hours away.

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Detector Tubes for Chemical Warfare Agents (CWAs)

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detector tubes for chemical warfare agents cwas

Detector TubesforChemical Warfare Agents (CWAs)

Presented by:

Gretchen B. Manning

Product Group ManagerPortable Instruments

© MSA 2002

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

Response to CWA Incident
chemical weapons for terrorists
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)

first responder detector needs
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

technologies for cwa detection
Technologies for CWA Detection

Ion Mobility Spectrometry (IMS)


Distinguishes among agent families

Detects at IDLH/10

$6 -12K

Pesky radioactive source

Sensitive to some “battlefield interferents”

technologies for cwa detection6
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

technologies for cwa detection7


Detects at IDLH/10 to IDLH

Discriminates among families of agents


Simple to use…go / no-go

Low false positive rate

Technologies for CWA Detection

Detector Tubes

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

What are Detector Tubes?
example of detector tube use h

reagent ampoule

indication layer

Example of Detector Tube Use (H)

Detector tube for




Chemically treated indication layer

Reagent ampoule

Pump to drawsample throughthe tube

example of detector tube use h10

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



detector tube chemistry h

mustard agent

Indicator (colorless)

developer (reagent)

complex (blue)

Detector Tube Chemistry (H)

Mustard Agent

how does nerve agent really work

How does nerve agent really work?

Humans and detector tubes have more in common than you think!

how does nerve agent work
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


  • 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
in summary

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…
so how does the human nervous system relate to detector tubes
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

example of detector tube use g
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

example of detector tube use g17

reagent 1



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
detector tube chemistry g








substrate (white layer)

enzyme (catalyst) in yellow layer

nerve agent stops the first reaction…no color change!

+ O2N - -S – S - -NO2





(CH3)3NCH2CH2S – S - -NO2 +

S - - NO2 S = =N




Detector Tube Chemistry (G)
detector tube target analytes
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)


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