2. Chemical Warfare Agents
• Most modern countries posses stockpiles of weaponized
agents
• Increasing threats from extremist countries and groups on
the usage of agents e.g. Al-Qaeda, North Korea
• Used as recently as 2013 in the Syrian capital
• Counter measures need to be taken
• Detectors need to be: Durable, selective, portable, cheap
2
3. Existing Techniques: IMS / MS
• Ion Mobility Spectroscopy
• Mass spectroscopy
• Disadvantages:
• Expensive
• Training
• Moderately large
3
4. Existing Techniques: Chemical tests
• Test papers
• Disadvantages
• Easily contaminated
• Subject to false positives
• Identify by human eye
• Enzymes
• Nerve agent immobilized-enzyme alarm detector (NAIAD)
• Disadvantages
• Poor shelf life
• Bulky
• Storage problems
4
5. HGV (Highly selective, Greatly enhanced
responses & times, Very easy to use)
• Developed by Dr. Ian Fallis Cardiff
• Very fast responses
• Small and easily portable
• Swabs are already in use in airports etc.
• Would be easy to integrate
5
6. Need For Project
• Colour change in swabs are very intense
• However very hard for humans to see slight colour change over time
• Swabs do not give an indication if antidote is needed
• Detector needed to inform user on impending danger
• Do not want to inject antidote if no presence of warfare agent, as can
lead to seizures and other side effects
N. B. Munro, A. P. Watson, K. R. Ambrose, and G.D. Griffin, Environmental Health Perspectives, 1990, 89, 205-215
(on left)
Mark I
NAAK kit
6
7. Aims of Project
• Begin to develop a sensor to detect significant colour
change over time
• Detectors need to be:
• Cheap
• Portable
• Small
• Simplistic
• Sensitive
• 2 methods approached:
• Image analysis program
• Potentially using a smart device (e.g. mobile phone)
• Spectroscopic analysis
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9. Calibrating Micrometer to Wavelengths
• First step to develop the spectroscopic analysis was to
calibrate the micrometer
• Achieved through spectroscopic analysis of coloured
filters with specific wavelengths
0 0.5 1 1.5 2
Absorbance/[arbitraryunit]
Micrometer position / m-6
Absorbance from Orange 550nm long pass filter
0 0.5 1 1.5 2
Absorbance/[arbitraryunit]
Micrometer Position / m-6
Absorbance from Green 495nm long pass filter
9
10. Calibrating Micrometer to Wavelengths
• From the previous graphs, points of intense absorbance
were found and analyzed to determine the exact
wavelength compared to the spectrometer
0.6 0.7 0.8 0.9 1 1.1
Absorbance/[arbitraryunit]
Micrometer position / m-6
Orange 550nm long pass Filter
1.15 1.2 1.25 1.3 1.35 1.4 1.45
Absorbance/[arbitraryunit]
Micrometer Position / m-6
Absorbance from Green 495nm long pass filter
10
11. Analysis of Formazan Complexes
• Calibrated spectrometer was now able to detect
absorbance based on micrometer positions
• The next step was to analyze real formazan complexes
• While also analyzing the sensitivity of the spectrometer
11
12. Analysis of Formazan Complexes
• Absorption becomes difficult to observe past a dilution
factor of 2 as the signal to noise ratio decreases as the
dilution factor increases
• Therefore a more sensitive analysis was proposed
0
0.2
0.4
0.6
0.8
1
1.2
0 0.5 1 1.5 2
Absorbance/[arbitraryunit]
Micrometer Position / m-6
Absorbance from Non diluted formazan
complex
0
0.05
0.1
0.15
0.2
0.25
0.3
0.35
0.4
0.45
0 0.5 1 1.5 2
Absorbance/[arbitraryunit]
Micrometer position / m-6
Absorbance from formazan complex at
dilution factor 2
0
0.02
0.04
0.06
0.08
0.1
0.12
0.14
0.16
0.18
0.2
0 0.5 1 1.5 2
Absorbance/[arbitraryunit]
Micrometer position / m-6
Absorbance from formazan complex at
dilution factor 4
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13. “Boxed” Analysis
• Moves a defined box along light spectrum seen through grating
• Gives a higher wavelength resolution by separating
wavelengths
• This removes light contamination as the box concentrates on a
particular wavelengths
13
14. “Boxed” Analysis
• Improves sensitivity of the spectrometer
• Very effective in measuring absorbance of complexes
• Sensitivity of spectrometer stops at a dilution factor 4
0 0.5 1 1.5 2
Absorbance/[arbirtaryunit]
Micrometer Position / m-6
Non diluted formazan complex
0 0.5 1 1.5 2
Absorbance/[arbitraryunit]
Micrometer Position / m-6
non diluted formazan complex (box analysis)
0 1 2
Absorbance/[arbitraryunit]
Micrometer position / m-6
formazan complex at dilution factor 2
(boxed analysis)
0 1 2
Absorbance/[arbitraryunit]
Micrometer position / m-6
formazan complex at dilution factor 2
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15. Image Analysis Program
• Program utilizes the CCID chip from a camera to analyze
colours of the solutions
• Exact wavelengths of the solutions cannot be found from the
pixels
• Approximate wavelengths are used instead, e.g. red vs non red
• An image is loaded to the program where it is converted to an
RGB
• It is then split into 3 separate image bands of red, green and
blue
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16. Image Analysis Program
• From the three split image bands, arrays of pixel values are
created and a histogram created depending on which colour is
selected
• Program used “kmeans” clustering to determine the most
dominant colours in an image
• A threshold was written in to the clustering to increase the
sensitivity
• Program will then inform the user if there is a danger
16
17. Moving Forward
• Moving forward with the
spectroscopic analysis:
• Using a SQUIGGLE motor
• Small LED as light source
• Replacing heavy steel components with
plastic
• Encasing spectrometer components
with a casing to improve signal to noise
ratio
17
18. Moving Forward
• Image analysis program:
• Adding a “centroiding” component to the program
• Finding LD50 of warfare agent, swab testing this and analyzing
• Developing to make more user friendly
• Using both methods in conjunction
• Conducting spectroscopic analysis
• Using program to identify clusters of light intensity
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