-
Forensic analysis of explosives
Youngeun Choi, Dario Remmler, Maximilian Ries, Felix Rösicke, Radwan Sarhan, Felix Stete, Zhiyang Zhang
-
Detecting and identifyingexplosives is of great importance
●Airport and airline security
●Demining
●Forensic analysis
●Removal of unexploded ordnance
Picture: Wo st 01/Wikipedia
Picture: MatthiasKabel/Wikipedia
Picture: Tom Oates/Wikipedia
Picture: Mark A. Moore/Wikipedia
-
Outline
● Forensic analysis
● Common explosives
■ Inorganic explosives● examples and sample preparation
● selected analytical techniques
■ Organic explosives containing Nitro-moieties● Principle of detection
● selected analytical techniques
■ Other important explosives
-
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?
-
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
-
Inorganic Explosives
Type Decomposition mechanism Characteristic ions
Ammonium nitrate 2 NH4NO3 → 4 H2O + 2 N2 + O2 NO3−, NH4+
Ammonium perchlorate 2 NH4ClO4 → Cl2 + 2 O2 + N2 + 4 H2O NO3−, ClO4-, NH4+
Pure compounds
Ignition needed!
-
Inorganic Explosives
Type Composition Characteristic ions
ANFO(Ammonium nitrate fuel oil)
NH4NO3, fuel oil (long chain hydrocarbons)
NO3−, NH4+, MeNH3+
Black powder Nitrates, sulfur, charcoal NO3−, SO42-, S2O32−
Na+, K+
Chlorate blends Chlorates, reducing agent(Metal powders, sugars etc.)
ClO3-, Cl-, Al3+, Na+, K+
Perchlorate blends Perchlorates, reducing agent(Metal powders, sugars etc.)
ClO4-, Cl-, Al3+, Na+, K+
Pure compounds Mixtures
Oxi
dizin
gsa
lt/ fu
el
-
Inorganic Explosives
● Sample preparation:
● Inorganic compounds: salts - soluble in water
● → Dissolve in water!
● (removal of organic compounds if necessary)
● further preparation strongly dependent on applied method
Source: Youtube
-
Inorganic Explosives
On-site analytics• Colorimetric reactions (wet-chemical ion specific reactions)
– Brown ring reaction: NO3-
– Berthelot reaction: NH4+
• Flame colouring
https://de.wikipedia.org/wiki/Ringprobe
Reaction Ion LOD Source
Brown ring NO3- 30 μg/ml Stevens 1966
Berthelot reaction NH4+ 10 ng/ml Tsuboi et al. 2002
http://www.chemische-experimente.com/Alkalimetalle.htm
Hubalek et al. 2007
-
Inorganic Explosives
Off-site analytics• Ion Exchange Chromatography
– fast– only quantitative when ion separate clearly
• Desorption Electro Flow-Focusing Ionization(DEFFI)-MS with CID– CID improves selectivity by breaking up adducts - elemental
ions can be preduced and detected more selectively– includes mapping possibilities– high instrumental effort
Technique Ion LOD Source
IECAl3+
ClO3-ClO4-
0.95 ng/l2 ng/ml
0.77 ng/ml
Gibson et al. 1991Binghui et al. 2006
Tian et al. 2003
DEFFI-MS K+Pb+
ClO3-
10 ng1 ng
300 pgForbes et al. 2014
Source: Forbes et al. 2014
-
Nitro compounds
Trinitrotoluene (TNT)
Nitroglycerin (NG)
Explosives with nitro-groups:
2 C7H5N3O6(s) 12 CO(g) + 5 H2(g) + 3 N2(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
-
Mass Spectrometry exibits extraordinary properties in explosive detection
Mass Spectrometry
QuadrupoleIontrap
Time-of-flight (TOF)Tandem based (MS/MS)
Modes
IonizationMatrix-assisted laser desorption/ionization
Electrospray ionizationChemical 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
-
Direct Analysis in Real Time is very useful forexamining surfaces
Direct Analysis in Real Time (DART)
Mechanism in Detail: Penning Ionization
M*+ S S+• + M + e-
He(23S) + H2O H2O+•+ He(11S) + electronH2O+•+H2O H3O++ OH•
H3O++ n H2O [(H2O)nH]+[(H2O)nH]++ S SH++nH2O
Source: Direct Analysis in Real Time (DARTtm) Mass Spectrometry Robert B. Cody, James A. Laramée, J. Michael Nilles, H. Dupont Durst
Sample
-
Atmospheric-pressure chemical ionizationuses 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
-
ESI/quadrupole HMX;RDX;PETN;Tertyl 170 fmol/μL Straub & Voyksner, 1993
APCI;MS/MS TNT; PETN; RDX 5 fg; 250 pg; 5 ng Evans 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; quadrupole TNT, 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 REVIEWMarko Ma¨kinen, Marjaana Nousiainen, and Mika Sillanpa¨a¨
Limits of detection
-
Raman EffectInelastic 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 SetupMeasuring the frequency-shift ωq=ωi±ωs• portable solutions• stand-off detection
-
Raman SpectroscopySamples for Raman
• fingerprints, fingernails• pure explosives
– aquaeous solutions– vapour for SERS
detectable through various window materialonly 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
-
Raman Spectroscopy
Raman stand-off PETN, RDX (>20m)TNT, UN (30m)DNT, TNT, RDX (7m)
-
IR SpectrumAbsorption at vibrational modes
• change in dipol moment• whole molecule (below 1300cm-1)• functional groups (above 1500cm-1)
– X-NO2 (vs, vas)
IR SpectroscopyBeveridge 2012 functional group symmetric vs asymmetric vas
C-NO2 1320-1390 cm-1 1510-1590 cm-1
Ring-NO2 1340-1370 cm-1 1520-1560 cm-1
C-O-NO2 1270-1285 cm-1 1640-1660 cm-1
N-NO2 1270-1310 cm-1 1530-1590 cm-1
http://www.sesame.org.jo
Experimental SetupMeasuring absorption in transmission or reflectance• FTIR (interferometer)• portable solutions• stand-off detection
-
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 for IR• pure explosives
– gases/solids betwen plates, pellets– aquaeous solutions
• compounds are difficultchromatography (MS better)
• reaction products after explosion– e.g. carbonates, thiocyanates
US8222604 B2
-
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?
-
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 bombingswww.globalresearch.ca
-
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
MSIonization, detection
Headspace Gas chromatography/ mass spectrometry (HS-GC/MS)
GCInjection,
separation
wikipedia.org
-
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
://w
ww
.labh
ut.c
om/
-
Immunosensor for TATP detection
Immunoassay:Biochemical test based on antibody/antigen interaction for qualitative and quantitative analysis.
Analyte, antibody and a detectable label
TATPimmunogenTATP Hapten-BSA conjugate
M. Walter, U. Panne, M. Weller, Biosensors, 2001, 1, 93 http://www.invitro-test.com/
-
Sensitivity and selectivity of TATP antibody
No cross reactivities with other explosives
M. Walter, U. Panne, M. Weller, Biosensors, 2001, 1, 93
Detection limit in the range of ng/L
-
Others - Dust explosionsDust explosions ; explosive combustion of dust cloudIf 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 Saftey and HazardInvesitagion Board (CSB)
Parnell, C. et al., J. Loss. Prevent. Proc. 2013, 26, 427
-
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-siteanalysis!
Forensic analysis of explosivesFoliennummer 2Foliennummer 3Foliennummer 4Foliennummer 5Foliennummer 6Foliennummer 7Foliennummer 8Foliennummer 9Foliennummer 10Foliennummer 11Foliennummer 12Foliennummer 13Foliennummer 14Foliennummer 15Foliennummer 16Foliennummer 17Foliennummer 18Foliennummer 19Foliennummer 20Foliennummer 21Foliennummer 22Foliennummer 23Foliennummer 24Immunosensor for TATP detectionFoliennummer 26Foliennummer 27Foliennummer 28