I. Francis Cheng, Derek F. Laine, Christopher Roske

1
Detection of Organic Peroxide Explosives Through
The Fenton Reaction

• I. Francis Cheng, Derek F. Laine, Christopher
  Roske
• University of Idaho
• Moscow, ID 83844-2343
• Email ifcheng_at_uidaho.edu
• Tel. [phone]
• Fax [phone]
• Homepage http//www.chem.uidaho.edu/faculty/ifche
  ng/
• Acknowledgement NSF-SGER

2
Triacetone Triperoxide (TATP)

• Wikipedia http//en.wikipedia.org/wiki/Acetone_per
  oxide
• Acetone peroxide (triacetone triperoxide,
  peroxyacetone, TATP, TCAP) is an organic peroxide
  and a primary high explosive.

3
Hexamethylenetriperoxide (HMTD)

• Wikipedia - http//en.wikipedia.org/wiki/Hexamethy
  lene_triperoxide_diamine

Oxley, J.C. Smith, J.L. Chen, H. Cioffi,
Eugene. Thermochim. Acta 2002, 388, 215-225.
4
Outline

• Background
• Dangers
• Recent News
• Need for Detection Systems
• Fast
• Field Portable (handheld)
• Selective and LOD
• Electrochemical Detection Via Fenton Reaction

5
TATP HMTD the threat

• Due to the cost and ease with which the
  precursors can be obtained, acetone peroxide is
  commonly manufactured by those without the
  resources needed to manufacture or buy more
  sophisticated explosives. When the reaction is
  carried out without proper equipment the risk of
  an accident is significant.
• http//en.wikipedia.org/wiki/Acetone_peroxide

6
TATP Ease of Synthesis

• 3H2O2 3CH3COCH3 ((CH3)2COO)3 3H2O
• Ice Bath
• 3 H2O2 (30 or more preferable)
• Acetone (paint thinner)
• H2SO4 (battery acid)

7
Ease of HMTD Synthesis

• http//business.fortunecity.com/executive/674/hmtd
  .html
• Hexamethylenetetramine Citric Acid H2O2 ?
  HMTD

8
TATP HMTD physiochemical characteristics

• HMTD
• Shock Sensitive
• Heat Sensitive
• Low VP

• TATP
• Shock Sensitive
• Heat Sensitive
• High V.P. 7 Pa _at_ 300K

• Neither have any commercial or military value.
• Propellants, Explosives, Pyrotechnics 30
  (2005)127
• J. Am. Chem. Soc. 2005, 127, 1146-1159

9
TATP Most Recent News

• NY Times Sept. 5, 2007
• FRANKFURT, Sept. 5 The German police have
  arrested three Islamic militants suspected of
  planning large-scale terrorist attacks against
  several sites frequented by Americans, including
  discos, bars, airports, and military
  installations.
• She said the suspects had amassed large amounts
  of hydrogen peroxide, the main chemical used to
  manufacture the explosives used in the suicide
  bombings in London in July 2005.

10
TATP HMTD London Subway Bombings

• July 7, 2005
• http//news.bbc.co.uk/nol/shared/spl/hi/pop_ups/05
  /uk_enl_1121567244/img/1.jpg

11
TATP HMTD Incidents

• 2006 London airline bombing plot HMTD
• 2005 - Joel Henry Hinrichs III University of
  Oklahoma. TATP.
• 2001 - Richard Reid, Shoe Bomber TATP
• 1999 - Millennium bomber Ahmed Ressam. 124 pounds
  of HMTD
• 1994/95 Bojinka Plot TATP? HMTD?
• 1994 Philippines Airlines - TATP
• 1980s present - West Bank Israel TATP
  Mother of Satan

12
TATP TSA Fluid Ban

• Effective November 10, 2006, the TSA has advised
  that travelers may now carry through security
  checkpoints travel-size toiletries (3.4
  ounces/100 ml or less) that fit comfortably in
  ONE, QUART-SIZE, clear plastic re-sealable bag.
• The 3-1-1 Kit contains six 2-1/2 oz and four
  1-1/2 oz flexible squeeze tubes, plus one 1-3/4
  oz Envirosprayer.
• Kit is also compliant with the new International
  Security Measures Accord.
• http//www.easytravelerinc.com/

13
TATP HMTD Detection - The Challenge

• The Need for a Fast Portable Detector
• Innocuous Appearing White Powder
• Dogs are only moderately successful at detection
  of TATP HMTD - Expensive
• Lacks Chromophoric Groups (not detectable by
  UV-vis absorbance)

14
TATP HMTD Detector Requirements

• Unknown Materials Public Safety, e.g. Airports
• High Selectivity Low Limits of Detection not
  Required
• Air Samples, e.g. Airports
• Moderate Selectivity Low Limits of Detection
  Required
• Debris at Post-Explosion Sites
• High Selectivity Low Detection Limits
• Field Portability

Schulte-Ladbeck, R. Vogel, M. Karst, URecent
methods for the determination of peroxide-based
explosivesAnal. Bioanal. Chem. 386 559-565
(2006)
15
TATP HMTD - Detectors

• IR-Raman
• High Selectivity Relatively High LOD
• Fluorescence/UV-vis Absorbance
• Low LOD requires tagging
• Ion Mobility
• Good Selectivity, moderate LOD
• HPLC or GC
• Excellent Selectivity and LOD

16
TATP HMTD State of Detectors

• Costs
• Lack of Field Portability
• Ideal Handheld Sensor
• May Require Knowledgeable User
• e.g. Commercial Glucose Sensors, electrochemical
  devices

17
The Fenton Reaction

• H2O2 e- ? HO HO-
• Fe(II) ? Fe(III) e-
• Fe(II) H2O2 ? Fe(III) HO HO-

H.J.H. Fenton. J. Chem. Soc. 1894, 65, 889. F.
Haber and J.J. Weiss. Proc. Roy. Soc. London,
Ser. A. 1934, 147, 332.
18
The Fenton Reaction

• FeIIIEDTA e- FeIIEDTA
• FeIIEDTA H2O2 FeIIIEDTA HO- HO (fast)
• H2O2 e- HO- HO (slow)

19
EC Voltammetry with the Fenton Reaction Mechanism

• Cyclic voltammetry
• 0.1 mM FeIIIEDTA
• 0.1M KCl, 0.1 M chloroacetic acid (pH3.3) under
  N2 purge
• 8 mM TBHP or H2O2
• 0 mM TBHP.

20
TATP HMTD Detection by Electrochemical Means

• Proposed Basis For Detection
• Fenton Reaction for Organic Peroxides
• RO-OR FeIIEDTA ? RO- RO FeIIIEDTA

21
TATP HMTD Electrochemical DetectionReaction
with Organic Peroxides is not Spontaneous

• RO-OR FeIIEDTA ? N.R.
• E0
• RO-OR e- ? RO- RO lt-0.5 V
• FeIIEDTA ? FeIIIEDTA e- 0.1 V
• Ecell Ecath Eanod -0.6 V

22
TATP HMTD Electrochemical DetectionReaction
with Peroxides and Hydroperoxides is Spontaneous

• E0
• RO-OH e- ? RO- HO 0.4 V
• HO-OH e- ? HO- HO 0.8 V
• FeIIEDTA RO-OH/HO-OH
• ?FeIIIEDTA RO/HO/H
• Requires that TATP HMTD be degraded

23
TATP Degradation to HOOH/ROOH

• Acid degradation
• TATP H ? H2O2 Products
• Concentrated HCl
• 1-10 minutes

24
HMTD Degradation

• HMTD ? products H2O2
• Rapid (almost immediate) Spontaneous
• With addition of FeIIIEDTA
• pH effect 2.1

25
TATP Cyclic Voltammograms after Acid Digestion
26
Chronoamperometry

• E- step -400 mV v. Ag/AgCl
• 1 mM FeIIIEDTA
• 0.1 NaAc/HAc buffer pH 3
• 40 Acetonitrile
• Vigorous Stirring
• 0.04 mM acid treated TATP
• B) 0 mM TATP

• Background
• FeIIIEDTA e- FeIIEDTA
• FeIIEDTA O2 FeIIIEDTA O2.-

27
TATP calibration curve

• The detection limit is 0.9 µM 3Sb/m,
• Sb standard deviation of blanks
• m slope of calibration curve
• Sensitivity of 0.025 mA/mM TATP.
• Background subtracted
• Error bars indicate one standard deviation.

28
HMTD analysis

• E- step -400 mV v. Ag/AgCl
• 1 mM FeIIIEDTA
• Vigorous Stirring
• Detection limit 30 µM 3Sb/m,
• Sb standard deviation of blanks
• m slope of calibration curve
• Error bars indicate one standard deviation.

Increasing HMTD
29
Detection of TATP in technical mixtures

• Significant concentrations of HOOH and ROOH.
• Provides Target for the Detection of Technical
  Mixtures
• TATP purification requires MeOH Recrystallization
  More Stable than Technical Mixtures

30
Detection of HOOH ROOH

• E0
• RO-OH e- ? RO- HO 0.4 V
• HO-OH e- ? HO- HO 0.8 V
• FeIIEDTA RO-OH/HO-OH ?FeIIIEDTA RO/HO/H
• Detection Limits
• H2O2 0.4 µM
• tert-butyl hydroperoxide 21 µM

31
Literature
Wang, Joseph et al, Analyst 2007, 132, 560-565.
Technique Pre-treatment Speed (mins) LOD Simultaneous Detection of TATP/HMTD Ref
EC Fenton TATP Acid 1-10 1 µM Yes This Work
EC Fenton HMTD None 0 30 µM Yes This Work
HRP Colorimetric UV 1 0.9 mM No 6
HRP Fluorescence UV 30 8 µM No 4
HPLC Fluorescence UV 15 2 µM Yes 3
Amperometric-PBME UV/laser 1 50nM No 7
Acid 1 55 nM No
Chronoamperometric/ PBME Acid 1 18 mM No
32
Other Needs for H2O2 Detection

• Glucose Detector
• Glucose H2O O2 ? Gluconic Acid H2O2
• H2O2 ? 2H O2 2e- (slow)
• Immobilized HRP
• Limited Linear Range to 3 mM

33
Advantages of H2O2 via Fenton Reaction

• This Work
• FeIIIEDTA e- FeIIEDTA (fast)
• FeIIEDTA H2O2 FeIIIEDTA HO- HO (fast)
• Does not require immobilization of enzymes
• Less Expensive
• Linear Range LOD 100 mM

34
Summary

• TATP - 0.9 µM LOD Instrumental
• HMTD - 30 µM LOD Method
• HOOH 0.4 µM LOD Instrumental
• ROOH 21 µM LOD Instrumental
• O2 interference
• FeIIEDTA O2 ? FeIIIEDTA O2.-
• HOOH/ROOH No Pretreatment
• Requires Acid Pretreatment
• TATP 1-10 min. Sample Pretreatment
• HMTD Instantaneous

35
Summary

• Proof of concept
• No modified electrodes or enzymes required.
  Reagents can stand up to long term storage.
• Allows for development of simple, handheld
  inexpensive devices, e.g. glucose sensors
• Not a stand-off detection device
• High TATP VP may allow for gas phase sensor

36
Future Work

• Elimination of O2 interference
• Metal Complex Reduction Potential
• Kinetics of H2O2 vs. O2 reduction
• Optimal Hydrolysis
• Design of probes
• Air Samples
• Liquid Sample

37
Acknowledgements

• National Science Foundation

38
Abstract - Detection of Organic Peroxide
Explosives through the Fenton Reaction

• There is an urgent need for methods and
  techniques that are able to detect quantitatively
  and qualitatively peroxide based explosives,
  especially triacetone triperoxide or TATP. The
  basic chemistries for such endeavor have not been
  fully described. This investigation will examine
  the electrochemical mediation of the Fenton
  Reaction as a basis for detection of this class
  of explosives. The mediation takes place as a
  result of the homogeneous Fenton Reaction and the
  electro-reduction of an FeIII complex to FeII
  followed by oxidation by either a hydroperoxide
  or hydrogen peroxide
• FeIIcomplex RO-OH ? FeIIIcomplex RO- HO
• FeIIcomplex HO-OH ? FeIIIcomplex HO- HO
• The current due to the electro-reduction of the
  FeIII complex is proportional to the square root
  of the peroxide concentration. The process is
  expected to be rapid, robust, and inexpensive. We
  will report on the detection limits, kinetics,
  optimal conditions for the degradation of TATP to
  hydroperoxides and H2O2, and the role of the
  chelate of that iron complex. The latter is based
  on considerations of the structure-activity
  relationships developed by cyclic voltammetric
  studies.