031115-Presentation_chemistryExplosives.pdf

Something else

1. Forensicanalysisofexplosives
Youngeun Choi, Dario Remmler, Maximilian Ries, Felix Rösicke, Radwan Sarhan, Felix Stete, Zhiyang Zhang

2. Detectingandidentifying
explosives isofgreatimportance
●Airport andairlinesecurity
●Demining
●Forensicanalysis
●Removalofunexplodedordnance
Picture: Wo st 01/Wikipedia
Picture: MatthiasKabel/Wikipedia
Picture: Tom Oates/Wikipedia
Picture: Mark A. Moore/Wikipedia

3. Outline
●Forensicanalysis
●Common explosives
■Inorganicexplosives
●examplesandsample preparation
●selectedanalyticaltechniques
■Organicexplosives containingNitro-moieties
●Principleofdetection
●selectedanalyticaltechniques
■Other importantexplosives

4. Forensic analysis
After an incident with an explosion:
Where was the source of the explosion?
Which explosive was used?
Where did the explosive come from?

5. Commonly used explosives
Inorganic explosives:Explosives with containing Nitro-
moieties:
Others:
Ammonium nitrate
+ S + CK
+
+
Black powder
Trinitrotoluene (TNT)
Nitroglycerin (NG)
Triacetone triperoxide (TATP)
Dust of flammable
materials

6. Inorganic Explosives
Type Decomposition mechanism Characteristic ions
Ammonium nitrate 2 NH
4NO
3→ 4 H
2O + 2 N
2+ O
2 NO
3
−, NH
4
+
Ammonium perchlorate2 NH
4ClO
4→ Cl
2+ 2 O
2+ N
2+ 4 H
2O NO
3
−, ClO
4
-, NH
4
+
Pure compounds
Ignition needed!

7. Inorganic Explosives
Type Composition Characteristicions
ANFO
(Ammonium nitrate fuel oil)
NH
4NO
3, fuel oil
(long chain hydrocarbons)
NO
3
−, NH
4
+, MeNH
3
+
Black powder Nitrates, sulfur, charcoal NO
3
−, SO
4
2-, S
2O
3
2−
Na
+
, K
+
Chlorate blends Chlorates, reducing agent
(Metal powders, sugars etc.)
ClO
3
-, Cl
-
,
Al
3+
, Na
+
, K
+
Perchlorate blendsPerchlorates, reducing agent
(Metal powders, sugars etc.)
ClO
4
-, Cl
-
,
Al
3+
, Na
+
, K
+
Pure compounds Mixtures
Oxidizingsalt/ fuel

8. Inorganic Explosives
●Sample preparation:
●Inorganiccompounds: salts-soluble in water
●→ Dissolvein water!
●(removaloforganiccompoundsifnecessary)
●furtherpreparationstronglydependenton appliedmethod
Source: Youtube

9. Inorganic Explosives
On-site analytics
•Colorimetricreactions(wet-chemicalionspecificreactions)
–Brown ring reaction: NO
3
-
–Berthelot reaction: NH
4
+
•Flame colouring
https://de.wikipedia.org/wiki/Ringprobe
Reaction Ion LOD Source
Brown ring NO
3
- 30 μg/ml Stevens 1966
Berthelot reaction NH
4
+ 10 ng/ml Tsuboiet al. 2002
http://www.chemische-experimente.com/Alkalimetalle.htm
Hubaleket al. 2007

10. Inorganic Explosives
Off-site analytics
•Ion Exchange Chromatography
–fast
–onlyquantitative whenionseparate clearly
•Desorption ElectroFlow-FocusingIonization(DEFFI)- MS withCID
–CID improvesselectivitybybreakingupadducts-elemental
ionscanbepreducedanddetectedmoreselectively
–includesmappingpossibilities
–high instrumental effort
Technique Ion LOD Source
IEC
Al
3+
ClO
3
-
ClO
4
-
0.95 ng/l
2 ng/ml
0.77 ng/ml
Gibson et al. 1991
Binghui et al. 2006
Tian et al. 2003
DEFFI-MS
K
+
Pb
+
ClO
3
-
10 ng
1 ng
300 pg
Forbes et al. 2014
Source: Forbes et al. 2014

11. Nitro compounds
Trinitrotoluene (TNT)
Nitroglycerin (NG)
Explosives with nitro-groups:
2 C
7H
5N
3O
6(s) 12 CO(g) + 5 H
2(g) + 3 N
2(g)+2 C(s)
Violent decomposition of TNT:
Relative to 1 kg TNT
TNT 1
Black powder 0,55
Dynamite 1,54
RDX 1,60
Octanitrocubane 2,38
Nuclear bomb (Nagasaki) 4500
R.E. Factor: Relates an explosive´s demolition power to
that of TNT

12. Mass Spectrometry exibits extraordinary
properties in explosive detection
Mass Spectrometry
Quadrupole
Iontrap
Time-of-flight (TOF)
Tandem based (MS/MS)
Modes
Ionization
Matrix-assistedlaserdesorption/ ionization
Electrosprayionization
Chemical ionization
...
Detection Limits
2,4,6-trinitrotoluene (TNT)* 3 pg/L
2,4-dinitrotoluene (DNT)* 90 ng/L
1,3,5-trinitro-1,3,5-triazacyclohexane*1 ng
PETN** 1 ng
Source: * Current trends in explosive detection techniques J. Sarah Caygill, Frank
Davis, Seamus P.J. Higson
** Direct detection of explosives on solid surfaces by mass spectrometry with an
ambient ion source based on dielectric barrier discharge Na Na, Chao Zhang, Mengxia
Zhao, Sichun Zhang, Chengdui Yang, Xiang Fang, Xinrong Zhang

13. Direct Analysis in Real Time is very useful for
examining surfaces
Direct Analysis in Real Time (DART)
Mechanism in Detail: Penning Ionization
M*+ S S
+•
+ M + e
-
He(2
3
S) + H
2O H
2O
+•
+ He(1
1
S) + electron
H
2O+•+H
2O H
3O
+
+ OH•
H
3O
+
+ n H
2O [(H
2O)
nH]
+
[(H
2O)
nH]
+
+ S SH
+
+nH
2O
Source: Direct Analysis in Real Time (DARTtm) Mass Spectrometry Robert B. Cody, James A. Laramée, J. Michael Nilles, H. Dupont Durst
Sample

14. Atmospheric-pressure chemical ionization
uses high temperatures for sampling
Atmospheric pressure chemical ionization interface (APCI)
Advantages:
-soft ionization method
-reduces the thermal decomposition
-possible to use a nonpolar solvent
Source: https://en.wikipedia.org/wiki/Atmospheric-pressure_chemical_ionization
Disadvantage:
-sample has to be in solution

15. ESI/quadrupole HMX;RDX;PETN;Tertyl 170 fmol/μL Straub & Voyksner, 1993
APCI;MS/MS TNT; PETN; RDX 5 fg; 250 pg; 5 ngEvans et al. 2002
DART nitroaromatics 2 μg/ml Song et al., 2009
LC-ESI RDX 2*10-8 M Sigman et al., 2005
APCI-CFI; quadrupoleTNT, RDX 10-20 ppt; 0.3 ppt Takada et al., 2002
DESI RDX 0.5 ng Cotte-Rodriguez & Cooks
2006
Detection limits are very low for mass
spectrometry methodes
Source: ON SPECTROMETRIC DETECTION TECHNOLOGIES FOR ULTRA -TRACES OF EXPLOSIVES: A REVIEW
Marko Ma¨kinen, Marjaana Nousiainen, and Mika Sillanpa¨ a¨
Limits of detection

16. Raman Effect
Inelastic scattering at vibrational modes
•change in polarizability
•distinct signatures = selectivity
•low efficiency P≈10
-7
–pulsed lasers
–UV higher QE (resonances)
–SERS
Raman Spectroscopy
Moore, Scharff 2008
Experimental Setup
Measuring the frequency- shift ω
q=ω
i±ω
s
•portable solutions
•stand-off detection

17. Raman Spectroscopy
Samples for Raman
•fingerprints, fingernails
•pure explosives
–aquaeous solutions
–vapour for SERS
detectable through various window material
only little preparation
Sajanlal, Pradeep 2012
Advantages
●selectivity
●sample preparation
●speed
●stand-off detection
●portable solutions
Disadvantages
●(sensitivity) → SERS
●ignition and eye-safety (Lasers)
●background elimination
●difficult in post-explosion analysis

18. Raman Spectroscopy
Raman stand- off PETN, RDX (>20m)
TNT, UN (30m)
DNT, TNT, RDX (7m)
<20μg/mm
-2
<500μg
<3mg
Moros et al. 2013
Gaft, Nagli 2008
Pacheco-Londoño et al. (2009)
Portable 23 incl. TNT, DNT, RDXpure, mg Lewis 2005
SERS on vapour TNT 5 ppb Sylvia et al. 2000
SERS on liquidsTNT, DNT
TNT, DNT, DPA, RDX
0,1 ppt
10
-7
M
Ko et al. 2009
Sajanlal, Pradeep 2012
Limits of detection

19. IR Spectrum
Absorption at vibrational modes
•change in dipol moment
•whole molecule (below 1300cm
-1
)
•functional groups (above 1500cm
-1
)
–X-NO
2(v
s, v
as)
IR Spectroscopy
Beveridge 2012functional groupsymmetric v
s asymmetric v
as
C-NO
2 1320-1390 cm
-1
1510-1590 cm
-1
Ring-NO
2 1340-1370 cm
-1
1520-1560 cm
-1
C-O-NO
2 1270-1285 cm
-1
1640-1660 cm
-1
N-NO
2 1270-1310 cm
-1
1530-1590 cm
-1
http://www.sesame.org.jo
Experimental Setup
Measuring absorption in transmission or
reflectance
•FTIR (interferometer)
•portable solutions
•stand-off detection

20. IR Spectroscopy
Advantages
●selectivity
●stand-off detection
●portable solutions
●characteristic for functional
groups/inorganic atoms
Disadvantages
●ignition
●absorption by air/water
●difficult in post-explosion analysis
●IR spectra sometimes similar
●low sensitivity (typical LOD ≥ 1mg)
Samples forIR
•pure explosives
–gases/ solidsbetwenplates, pellets
–aquaeoussolutions
•compoundsaredifficult
chromatography(MS better)
•reactionproductsafter explosion
–e.g. carbonates, thiocyanates
US8222604 B2

21. Triacetone triperoxide (TATP)
Combustible dust
Other explosives
There are other explosives out there that do not fit in the two categories shown before!
So, what happens in these cases?

22. Others - Organic Peroxides
Triacetone triperoxide, TATP
❏Primary explosive; Highly volatile, susceptible to heat, shock, or friction
❏Terrorists’ favorite explosive
❏Lack of Nitro groups
❏Home-made explosive:
July 2005 London bombings
www.globalresearch.ca

23. TATP traces detection in post- explosion
debris by HS-GC/MS
Volatile compounds are separated according to their partitioning behaviour
between mobile gas and stationary phase in the column. Identification of
the analyte happens at the mass spectrometer detector
Unlikely that 2 different
molecules behave similar
in both techniques.
Transfer
line
MS
Ionization,
detection
Headspace Gas chromatography/ mass spectrometry (HS-GC/MS)
GC
Injection,
separation
wikipedia.org

24. Headspace sampling:
analysis of the gas phase in the headspace above the sample.
Post-explosion debris(soil, glass and metals) collected from the
area of explosion in a glass container and heated. Then, a sample
from the headspace is injected to GC/MS.
m/z [M-1]
Detection limit of
1 nanogram
TATP traces detection in post- explosion
debris by HS-GC/MS
Stambouli A. et al., Forensic Sci
Int.,2004, 146S, S191
http://www.labhut.com/

25. Immunosensor for TATP detection
Immunoassay:
Biochemical test based on antibody/antigen
interaction for qualitative and quantitative
analysis.
Analyte, antibody and a detectable label
TATP
immunogen
TATP Hapten-
BSA conjugate
M. Walter, U. Panne, M. Weller,
Biosensors, 2001, 1, 93
http://www.invitro-test.com/

26. Sensitivity and selectivity of TATP
antibody
No cross reactivities
with other
explosive
s
M. Walter, U. Panne, M. Weller,
Biosensors, 2001, 1, 93
Detection limit in the
range of ng/L

27. Others - Dust explosions
Dust explosions ; explosive combustion of dust cloud
If particle size is less than 500 μm and suspended in air, the combustion rate is very
fast and the energy required for ignition very small → Violent combustion!
ASTM test methods: well-dispersed dust cloud is formed in a 20 L chamber, nearly spherical
in shape, and subjected to a strong pyrotechnic ignition souce. Resulting pressure and rate of
pressure rise are measured.
U.S. Chemical SafteyandHazard
InvesitagionBoard (CSB)
Parnell, C. et al., J. Loss.
Prevent. Proc. 2013, 26, 427

28. Summary
Method
Compound
Mass
Spectrometry
Vibrational
Spectroscopy Others
Inorganic Salts/
Mixtures
DEFFI
SERS/IR
Colorimetric reactions
Nitrogen containing
compounds
DART
Immunoassays and other
techniques
Peroxides GC/MS Immunoassays
Sample condition
Solid (surfaces)
Liquid (dissolved)
Gaseous
all phases
Sensitivity! Remote/
nondestructive!
Instant on- site
analysis!