I. Francis Cheng, Derek F. Laine, Christopher Roske University of Idaho Moscow, ID Tel.: Fax: Homepage: Acknowledgement: NSF-SGER Pittcon 2008 Session University of Idaho, IF Cheng, DF Laine, C Roske 1 Detection of Organic Peroxide Explosives Through The Fenton Reaction

Triacetone Triperoxide (TATP) Pittcon 2008 Session University of Idaho, IF Cheng, DF Laine, C Roske 2 Wikipedia Acetone peroxide (triacetone triperoxide, peroxyacetone, TATP, TCAP) is an organic peroxide and a primary high explosive.organic peroxidehigh explosive

Hexamethylenetriperoxide (HMTD) Pittcon 2008 Session University of Idaho, IF Cheng, DF Laine, C Roske 3 Wikipedia - Oxley, J.C.; Smith, J.L.; Chen, H.; Cioffi, Eugene. Thermochim. Acta 2002, 388,

Outline Pittcon 2008 Session University of Idaho, IF Cheng, DF Laine, C Roske 4 Background Dangers Recent News Need for Detection Systems Fast Field Portable (handheld) Selective and LOD Electrochemical Detection Via Fenton Reaction

TATP & HMTD – the threat Pittcon 2008 Session University of Idaho, IF Cheng, DF Laine, C Roske 5 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.

TATP – Ease of Synthesis Pittcon 2008 Session University of Idaho, IF Cheng, DF Laine, C Roske 6 3H 2 O 2 + 3CH 3 COCH 3 = ((CH 3 ) 2 COO) 3 + 3H 2 O Ice Bath 3% H 2 O 2 (30% or more preferable) Acetone (paint thinner) H 2 SO 4 (battery acid)

Ease of HMTD Synthesis Pittcon 2008 Session University of Idaho, IF Cheng, DF Laine, C Roske 7 Hexamethylenetetramine + Citric Acid + H 2 O 2  HMTD

TATP & HMTD – physiochemical characteristics Pittcon 2008 Session University of Idaho, IF Cheng, DF Laine, C Roske 8 TATP Shock Sensitive Heat Sensitive High V.P K HMTD Shock Sensitive Heat Sensitive Low VP Neither have any commercial or military value. Propellants, Explosives, Pyrotechnics 30 (2005)127 J. Am. Chem. Soc. 2005, 127,

TATP – Most Recent News Pittcon 2008 Session University of Idaho, IF Cheng, DF Laine, C Roske 9 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.

TATP & HMTD – London Subway Bombings Pittcon 2008 Session University of Idaho, IF Cheng, DF Laine, C Roske 10 July 7,

TATP & HMTD Incidents Pittcon 2008 Session University of Idaho, IF Cheng, DF Laine, C Roske – London airline bombing plot – HMTD Joel Henry Hinrichs III – University of Oklahoma. – TATP Richard Reid, Shoe Bomber – TATP Millennium bomber Ahmed Ressam. 124 pounds of HMTD 1994/95 – Bojinka Plot – TATP? HMTD? 1994 – Philippines Airlines - TATP 1980’s – present - West Bank Israel – TATP “Mother of Satan”

TATP – TSA Fluid Ban Pittcon 2008 Session University of Idaho, IF Cheng, DF Laine, C Roske 12 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 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.

TATP & HMTD Detection - The Challenge Pittcon 2008 Session University of Idaho, IF Cheng, DF Laine, C Roske 13 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)

TATP & HMTD – Detector Requirements Pittcon 2008 Session University of Idaho, IF Cheng, DF Laine, C Roske 14 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, U Recent methods for the determination of peroxide-based explosives Anal. Bioanal. Chem (2006)

TATP & HMTD - Detectors Pittcon 2008 Session University of Idaho, IF Cheng, DF Laine, C Roske 15 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

TATP & HMTD – State of Detectors Pittcon 2008 Session University of Idaho, IF Cheng, DF Laine, C Roske 16 Costs Lack of Field Portability Ideal – Handheld Sensor May Require Knowledgeable User e.g. Commercial Glucose Sensors, electrochemical devices

The Fenton Reaction Pittcon 2008 Session University of Idaho, IF Cheng, DF Laine, C Roske 17 H 2 O 2 + e -  HO + HO - Fe(II)  Fe(III) + e - Fe(II) + H 2 O 2  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.

The Fenton Reaction Pittcon 2008 Session University of Idaho, IF Cheng, DF Laine, C Roske 18 Fe III EDTA + e - = Fe II EDTA Fe II EDTA + H 2 O 2 = Fe III EDTA + HO - + HO ∙ (fast) H 2 O 2 + e - = HO - + HO ∙ (slow)

EC’ Voltammetry with the Fenton Reaction Mechanism Pittcon 2008 Session University of Idaho, IF Cheng, DF Laine, C Roske 19 Cyclic voltammetry 0.1 mM Fe III EDTA 0.1M KCl, 0.1 M chloroacetic acid (pH=3.3) under N 2 purge a) 8 mM TBHP or H 2 O 2 b) 0 mM TBHP. a b

TATP & HMTD – Detection by Electrochemical Means Pittcon 2008 Session University of Idaho, IF Cheng, DF Laine, C Roske 20 Proposed Basis For Detection Fenton Reaction for Organic Peroxides RO-OR + Fe II EDTA  RO - + RO· + Fe III EDTA

TATP & HMTD – Electrochemical Detection Reaction with Organic Peroxides is not Spontaneous Pittcon 2008 Session University of Idaho, IF Cheng, DF Laine, C Roske 21 RO-OR + Fe II EDTA  N.R. E 0 RO-OR + e -  RO - + RO·<-0.5 V Fe II EDTA  Fe III EDTA + e-0.1 V E cell = E cath – E anod -0.6 V

TATP & HMTD – Electrochemical Detection Reaction with Peroxides and Hydroperoxides is Spontaneous Pittcon 2008 Session University of Idaho, IF Cheng, DF Laine, C Roske 22 E 0 RO-OH + e -  RO - + HO·≈0.4 V HO-OH + e -  HO - + HO·0.8 V Fe II EDTA + RO-OH/HO-OH  Fe III EDTA + RO∙/HO∙/H + Requires that TATP & HMTD be degraded

TATP – Degradation to HOOH/ROOH Pittcon 2008 Session University of Idaho, IF Cheng, DF Laine, C Roske 23 Acid degradation TATP + H +  H 2 O 2 + Products Concentrated HCl 1-10 minutes

HMTD Degradation Pittcon 2008 Session University of Idaho, IF Cheng, DF Laine, C Roske 24 HMTD  products + H 2 O 2 Rapid (almost immediate) & Spontaneous With addition of Fe III EDTA pH effect – 2.1

TATP – Cyclic Voltammograms after Acid Digestion Pittcon 2008 Session University of Idaho, IF Cheng, DF Laine, C Roske 25 A B Figure 1. Cyclic voltammograms of two solutions both containing 10 mM TATP and 1 mM Fe III EDTA under dearated conditions, 30 mV/s. A) Acid treated TATP. B) Non-acid treated TATP.

Chronoamperometry Pittcon 2008 Session University of Idaho, IF Cheng, DF Laine, C Roske 26 Background: Fe III EDTA + e - = Fe II EDTA Fe II EDTA + O 2 = Fe III EDTA + O 2.- E- step = -400 mV v. Ag/AgCl 1 mM Fe III EDTA 0.1 NaAc/HAc buffer pH 3 40% Acetonitrile Vigorous Stirring A) 0.04 mM acid treated TATP B) 0 mM TATP B A

TATP calibration curve Pittcon 2008 Session University of Idaho, IF Cheng, DF Laine, C Roske 27 The detection limit is 0.9 μM = 3S b /m, S b = standard deviation of blanks m = slope of calibration curve Sensitivity of mA/mM TATP. Background subtracted Error bars indicate one standard deviation.

HMTD analysis Pittcon 2008 Session University of Idaho, IF Cheng, DF Laine, C Roske 28 Increasing [HMTD] E- step = -400 mV v. Ag/AgCl 1 mM Fe III EDTA Vigorous Stirring Detection limit 30 μM = 3S b /m, S b = standard deviation of blanks m = slope of calibration curve Error bars indicate one standard deviation.

Detection of TATP in technical mixtures Pittcon 2008 Session University of Idaho, IF Cheng, DF Laine, C Roske 29 Significant concentrations of HOOH and ROOH. Provides Target for the Detection of Technical Mixtures TATP purification requires MeOH Recrystallization – More Stable than Technical Mixtures

Detection of HOOH & ROOH Pittcon 2008 Session University of Idaho, IF Cheng, DF Laine, C Roske 30 E 0 RO-OH + e -  RO - + HO·≈0.4 V HO-OH + e -  HO - + HO·0.8 V Fe II EDTA + RO-OH/HO-OH  Fe III EDTA + RO∙/HO∙/H + Detection Limits H 2 O μ M tert-butyl hydroperoxide21 μ M

Literature Pittcon 2008 Session University of Idaho, IF Cheng, DF Laine, C Roske 31 Technique Pre- treatment Speed (mins) LOD Simultaneous Detection of TATP/HMTD Ref EC’ Fenton TATP Acid1-101 μMYesThis Work EC’ Fenton HMTD None030 μMYesThis Work HRP Colorimetric UV10.9 mMNo6* HRP Fluorescence UV308 μMNo4* HPLC Fluorescence UV152 μMYes3* Amperometric- PBME UV/laser150nMNo7* “Acid155 nMNo* Chronoampero metric/ PBME Acid118 mMNo* *Wang, Joseph et al, Analyst 2007, 132,

Other Needs for H 2 O 2 Detection Glucose Detector Glucose + H 2 O + O 2  Gluconic Acid + H 2 O 2 H 2 O 2  2H + + O 2 + 2e - (slow) Immobilized HRP Limited Linear Range to 3 mM Pittcon 2008 Session University of Idaho, IF Cheng, DF Laine, C Roske 32

Advantages of H 2 O 2 via Fenton Reaction This Work: Fe III EDTA + e - = Fe II EDTA (fast) Fe II EDTA + H 2 O 2 = Fe III EDTA + HO - + HO ∙ (fast) Does not require immobilization of enzymes Less Expensive Linear Range LOD – 100 mM Pittcon 2008 Session University of Idaho, IF Cheng, DF Laine, C Roske 33

Summary Pittcon 2008 Session University of Idaho, IF Cheng, DF Laine, C Roske 34 TATP µM LOD Instrumental HMTD - 30 µM LOD Method HOOH – 0.4 µM LOD Instrumental ROOH – 21 µM LOD Instrumental O 2 interference Fe II EDTA + O 2  Fe III EDTA + O 2.- HOOH/ROOH – No Pretreatment Requires Acid Pretreatment TATP – 1-10 min. Sample Pretreatment HMTD – Instantaneous

Summary Pittcon 2008 Session University of Idaho, IF Cheng, DF Laine, C Roske 35 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

Future Work Pittcon 2008 Session University of Idaho, IF Cheng, DF Laine, C Roske 36 Elimination of O 2 interference Metal Complex Reduction Potential Kinetics of H 2 O 2 vs. O 2 reduction Optimal Hydrolysis Design of probes Air Samples Liquid Sample

Acknowledgements National Science Foundation Pittcon 2008 Session University of Idaho, IF Cheng, DF Laine, C Roske 37

Abstract - Detection of Organic Peroxide Explosives through the Fenton Reaction Pittcon 2008 Session University of Idaho, IF Cheng, DF Laine, C Roske 38 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 Fe III complex to Fe II followed by oxidation by either a hydroperoxide or hydrogen peroxide: Fe II complex + RO-OH  Fe III complex + RO - + HO∙ Fe II complex + HO-OH  Fe III complex + HO - + HO∙ The current due to the electro-reduction of the Fe III 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 H 2 O­ 2, 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.