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![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(23S) + H2O H2O+•+ He(11S) + electron
H2O+•+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](https://image.slidesharecdn.com/031115-presentationexplosives-240814070614-68339cec/85/031115-Presentation_chemistryExplosives-pdf-13-320.jpg)
![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/](https://image.slidesharecdn.com/031115-presentationexplosives-240814070614-68339cec/85/031115-Presentation_chemistryExplosives-pdf-24-320.jpg)
031115-Presentation_chemistryExplosives.pdf
- 1. Forensic analysis ofexplosives Youngeun Choi, Dario Remmler, Maximilian Ries, Felix Rösicke, Radwan Sarhan, Felix Stete, Zhiyang Zhang
- 2. Detecting and identifying explosivesis 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
- 3. Outline ●Forensic analysis ●Common explosives ■Inorganicexplosives ● examples and sample preparation ● selected analytical techniques ■Organic explosives containing Nitro-moieties ● Principle of detection ● selected analytical techniques ■Other important explosives
- 4. Forensic analysis After anincident with an explosion: Where was the source of the explosion? Which explosive was used? Where did the explosive come from?
- 5. Commonly used explosives Inorganicexplosives: Explosives with containing Nitro- moieties: Others: Ammonium nitrate + S + C K ++ Black powder Trinitrotoluene (TNT) Nitroglycerin (NG) Triacetone triperoxide (TATP) Dust of flammable materials
- 6. Inorganic Explosives Type Decompositionmechanism 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!
- 7. Inorganic Explosives Type CompositionCharacteristic ions ANFO (Ammonium nitrate fuel oil) NH4NO3, fuel oil (long chain hydrocarbons) NO3 −, NH4 +, MeNH3 + Black powder Nitrates, sulfur, charcoal NO3 −, SO4 2-, S2O3 2− 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 Oxidizing salt/ fuel
- 8. Inorganic Explosives ● Samplepreparation: ● Inorganic compounds: salts - soluble in water ● → Dissolve in water! ● (removal of organic compounds if necessary) ● further preparation strongly dependent on applied method Source: Youtube
- 9. 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
- 10. 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 IEC Al3+ ClO3 - ClO4 - 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+ ClO3 - 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 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
- 12. Mass Spectrometry exibitsextraordinary properties in explosive detection Mass Spectrometry Quadrupole Iontrap Time-of-flight (TOF) Tandem based (MS/MS) Modes Ionization Matrix-assisted laser desorption/ionization Electrospray ionization 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 inReal Time is very useful for examining surfaces Direct Analysis in Real Time (DART) Mechanism in Detail: Penning Ionization M*+ S S+• + M + e- He(23S) + H2O H2O+•+ He(11S) + electron H2O+•+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
- 14. Atmospheric-pressure chemical ionization useshigh 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 170fmol/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 REVIEW Marko Ma¨kinen, Marjaana Nousiainen, and Mika Sillanpa¨a¨ Limits of detection
- 16. Raman Effect Inelastic scatteringat 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 ωq=ωi±ωs • portable solutions • stand-off detection
- 17. Raman Spectroscopy Samples forRaman • 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-offPETN, 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, RDX pure, mg Lewis 2005 SERS on vapour TNT 5 ppb Sylvia et al. 2000 SERS on liquids TNT, 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 atvibrational modes • change in dipol moment • whole molecule (below 1300cm-1) • functional groups (above 1500cm-1) – X-NO2 (vs, vas) IR Spectroscopy Beveridge 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 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 for IR • pure explosives – gases/solids betwen plates, pellets – aquaeous solutions • compounds are difficult chromatography (MS better) • reaction products after explosion – e.g. carbonates, thiocyanates US8222604 B2
- 21. Triacetone triperoxide (TATP) Combustibledust 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 - OrganicPeroxides 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 detectionin 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 ofthe 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 TATPdetection 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 selectivityof 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
- 27. Others - Dustexplosions 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 Saftey and Hazard Invesitagion Board (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 Colorimetricreactions 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!