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Fires & Explosions > Lecture 7 > Flashcards

Lecture 7 Flashcards

1
Q

How does a chemiluminescence detector work?

A

Different N groups have different chemiluminscence

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2
Q

Rewatch section on TEA ANALYSER

A

Lecture 7

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3
Q

What are the advantages of the TEA system?

A
  • Picogram limit of detection (LOD)
  • Simple 🡪 easy to use and maintain
  • Fast
  • Reliable
  • Robust evidence
  • No known false positives despite decades of use
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4
Q

What columns are used in TEA?

A
  • BP1 (Non-Polar)
  • BP2 (Slightly polar)
  • CPSIL19 (Polar)
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5
Q

BP2 column

A
  • Only very slightly polar
  • Changing SP to have a small amount of phenyl groups instead of methyl
  • Difference in polarity is enough to slightly shift retention times
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6
Q

CPSIL19 Column

A
  • Not actually very polar but it’s more polar than the others
  • Introduces small amount of phenyl groups and Si-CN groups
  • Will increase the retention times if they are more polar
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7
Q

What is the importance of the 3 different columns in TEA?

A
  • If all three indicate the presence of an explosive the analysis is considered trustworthy
  • The same experiment is done 3 times using 3 columns of slightly different polarity
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8
Q

What are the reference compounds in TEA?

A

Reference compounds are well-known compounds containing nitro functionality

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9
Q

How does TEA work?

A

Different explosives and taggants have different retention times which are known

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10
Q

What does TEA detect?

A

Nitrogen-containing groups

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11
Q

What is the process for each column in TEA?

A
  1. Run a standard of the explosive we’re interested in + Internal Standard
  2. Run a blank + Internal Standard
  3. Run sample + Internal Standard
  4. Run a standard of the explosive we’re interested in + Internal Standard
  5. Calculate %RRT Difference
  6. Apply Acceptance Criterion
  7. Confirm on two other systems
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12
Q

BP1 Column

A

Non-polar column

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13
Q

How do you calculate Relative Retention Time (RRT)?

A

Look at retention time of the sample and divide by the retention time of the reference compound

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14
Q

How do you calculate % RT difference?

A

((RRT of Sample - RRT of standard) / RRT of Standard) x 100

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15
Q

What does the %RT difference tell us?

A
  • How close is the sample retention time vs standard retention time
  • This value gives us an idea about how confident that is it is the sample we believe it is
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16
Q

What should the difference be less than for %RT Difference?

A

The difference should be less than 0.50%

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17
Q

How do you calculate the mass of the sample injected?

A

Mass of sample injected = Mass of the standard injected x (Peak area of sample / Peak area of standard)

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18
Q

Total mass equation

A

Total mass = mass injected x (Total volume of sample / volume injected)
- Rewatch lecture to check values

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19
Q

What is the main technique used for explosive compounds containing nitrogen?

A
  • TEA
  • ADD TO THIS!
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20
Q

What are FTIR and Raman used for when investigating explosive compounds?

A
  • They could be used to identify specific functional groups
    within explosive compounds
  • Useful for non-UB active and non-nitrogen organic-based explosives
  • Can detect the presence of TATP
  • These methods are typically used in combination with other techniques
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21
Q

What is the drawback of using FTIR and Raman (IR radiation techniques)

A
  • They are bad for complex mixtures as the spectra get messy and hard to interpret
  • TEA is better for nitrogen-containing groups
  • Not great for UV-active explosives
  • Other methods exist to analyse inorganic techniques
22
Q

What technique is useful for the analysis of inorganic explosive species?

A

SEM-EDX

23
Q

What can SEM-EDX be used for?

A
  • SEM-EX is widely used for inorganic species
  • Inorganic fuels (Mg, S, Al)
  • Inorganic oxidizers (KClO4, KNO3, NH4NO3)
  • Microscopy allows us to take images of sample so we can look at different positions
  • EDX can identify the chemical composition so we can identify the different elements present
24
Q

What are the advantages of SEM-EDX?

A
  • Non-destructive - in reality its hard to mount sample without damaging them but they can potentially be used again for repeat analysis
  • Area mapping 🡪 can observe sample inhomogeneity
25
Q

What are the limitations of SEM-EDX?

A
  • Only gives element and oxidation state
  • Not the highest sensitivity in comparison to other techniques which can be a limitation for trace analysis
  • Doesn’t give usw an idea about where the other elements are coming from
26
Q

What technique provides a higher sensitivity over SEM-EDX?

A

X-ray photoelectron spectroscopy (XPS) is an alternative technique that provides higher sensitivity but cannot be used for mapping

27
Q

How can inorganic species be separated?

A
  • Ion exchange liquid chromatography
  • Capillary electrophoresis
  • Using both techniques can be helpful for identifying and quantifying the different inorganic complexes and making sure we’ve identified the complexes correctly
28
Q

Ion exchange liquid chromatography

A
  • Used to separate inorganic species
  • Higher charge elutes slower
  • Separates based on the charge
  • Can be used for more inorganic complexes
29
Q

Capillary electrophoresis

A
  • Separates inorganic species
  • Electric field separates ions based on size and charge
  • We get slightly different elution order with capillary electrophoresis
30
Q

How can you detect fuels and accelerants?

A
  • GC with a flame ionisation detector (FID)
  • Lighter fuel analysis can be analysed by headspace GC-FID
31
Q

What are the two purposes of explosives legislation?

A
  • Health and Safety
  • Control and safe use of legitimately held explosives 🡪 e.g. 1875 Explosives Act
  • Criminal Activity
  • Intent to cause harm 🡪 e.g. 1883 Explosive Substances Act
32
Q

1883 Explosive Substances Act

A

Offences:
- Causing an explosion likely to endanger life and property
- Any act with intent to cause an explosion
- Making or keeping explosives with intent to endanger
- Making or keeping explosives under suspicious circumstances

33
Q

What does the ‘explosive substance’ term include in the 1883 explosive substances act?

A

“The expression ‘explosive substance’ shall be deemed to include any materials for making any explosive substance; also any apparatus, machine, implement or materials used, or intended to be used, or adapted for causing, or aiding in causing, any explosion in or with any explosive substance; also any part of any such apparatus, machine or implement”

34
Q

Where does the burden of proof lie in the 1883 Explosive Substances Act?

A
  • The burden of proof is with the accused
  • If you are found to have explosive materials, it is up to you to prove that you don’t intend to use it for illegal purposes (not tending to cause harm)
35
Q

What was the problem with the 1883 Explosive Substances Act?

A

It didn’t define what an explosive was

36
Q

How did they overcome the issue with the 1883 Explosive Substances Act?

A

They made an amendment that listed the different types of explosives but it’s not all-encompassing as there are lots of other things that could be used as an explosive to cause harm

37
Q

What case introduced the amendment of what an explosive was for the 1833 Explosives Substances Act?

A
  • R vs Wheatley 1979
  • “gun powder, nitroglycerine, dynamite, gun-cotton, blasting powders, fulminate of mercury or of other metals, coloured fires and every other substance, whether similar to those above mentioned or not, used or manufactured with a view to producing a practical effect by explosion or a pyrotechnic effect”
38
Q

1991 Montreal Convention

A
  • More restrictions were introduced relating to the use of plastic explosives
  • The use of taggants was introduced
39
Q

2003 Ammonium Nitrate Regulations

A

Only farmers could obtain ammonium nitrate in volumes higher than 16%

40
Q

EU 98/2014 and Control of Explosive Precursors Act 2014

A

Restrictions on peroxides

41
Q

Regulated/reported precursors

A

Controlled % (w/w)
H2O2 = 12%
Nitromethane = 30%
HNO3 = 3%
Na/KClO3 = 40%
KClO4 = 40%

42
Q

First example of banning membership of an organisation (IRA and INLA)

A

Counter Terrorist Legislation

43
Q

Counter-terrorist legislation

A
  • Complimentary to Explosives Act
  • First example of banning membership of an organisation (IRA and INLA)
  • It was considered an offence to commission, prepare or instigate terrorist activity
  • Introduced detention without charge for 48 hours and 5 days with ministerial approval
  • This was introduced in the 1970s
44
Q

2000 Terrorist Act / 2005 Prevention of Terrorism Act

A
  • The potential to make explosives had to be proved it wasn’t for the use of harmful purposes
  • Incitement, training and possession of documents were considered new offences
  • A broader definition of terrorism was changed to “causing fear in the pursuit of political objectives”
  • Proscribed organisations were extended beyond Ireland
  • Band 1 Offences were introduced
45
Q

What are band 1 offences under the 2000 terrorist act / 2005 prevention of terrorism act

A

Band 1 offences:
- Terrorist murder
- Explosive substances offences
- Preparation for terrorism
- Possession of material for the purpose of terrorism

46
Q

2006 / 2008 legislation

A
  • New offence 🡪 ‘glorifying’ terrorism/disseminating terrorist publications (Al-Muhajiroun)
  • Detention without charge now 28 days and remains the same now (Labour Home Secretary wanted 90)
  • Detention time was extended due to cases becoming more complex
  • Can continue to question suspects after being charged
  • DNA and fingerprints taken from those subject to a ‘control order’
    (Often those suspected of terrorism but limited evidence against them)
47
Q

What do the codes of practise and conduct lay out?

A

They outline the requirements for being an expert witness

48
Q

What are the requirements for being an expert witness in relation to terrorism?

A
  • An expert witness only requires “skills beyond those of ordinary people enjoying ordinary pursuits”
  • Presents relevant evidence (including opinion evidence.
    even allowed to give specialist hearsay evidence!)
  • If you’re working in an explosive analysis lab and you had a conversation with a supervisor who had an expertise that guided you on how to present or conduct your analysis, you can use this as justification as to why you’ve done something.
49
Q

What are duties of an expert witness?

A

To provide evidence which is:
- Independent
- Unbiased
- Impartial
- Objective
- Present their evidence, what they’ve done and why.
- Not to act as an advocate or fact finder

50
Q

What is the key thing related to explosive legislation and counter-terrorism legislation?

A
  • There are specific codes of practice that we have to adhere to if we’re going to collect and present that evidence in court.
  • These include standing operating procedures (SOPs), ISO 17025, etc

Fires & Explosions (18 decks)

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