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The many Wonders of FeEDTA: Room Temperature Incineration of Pollutants, and The Detection of Peroxide Based Explosives Frank Cheng Associate Professor of Chemistry University of Idaho Moscow, ID 83844-2343 Email: [email protected] Tel.: 208-885-6387 Fax: 208-885-6173 Homepage: http://www.chem.uidaho.edu/faculty/ifcheng/ 11 September 2007 University of Idaho 1 Outline Background and History of EDTA I] Room Temperature and Pressure Combustion of Organic Pollutants and Nerve Agent Surrogates – The Search for a Green Oxidant II] A Detector for Peroxide-Based Explosives III] A Model for the Role of Calcium and Zinc in Biological Oxidations 11 September 2007 University of Idaho 2 EDTA – A brief history Ethylenediaminetetraacetic acid 1930’s Ferdinand Munz first synthesizes EDTA as a substitute for amino acids in textile processing. COOH N COOH COOH Annual Production 100,000 metric tons. http://www.chm.bris.ac.uk/motm/edta/edtah.ht m 11 September 2007 University of Idaho N COOH 3 EDTA – Modern Uses http://en.wikipedia.org/wiki/EDTA Industrial cleaning: complexation of Ca and Mg ions, binding of heavy metals. Detergents: complexation of Ca and Mg (reduction of water hardness). Pulp and paper industry: complexation of heavy metals during chlorine-free bleaching, stabilization of hydrogen peroxide. Textile industry: complexation of heavy metals, bleach stabilizer. Food: added as preservative to prevent catalytic oxidation by metal ions or stabilizer and for iron fortification. Personal care: added to cosmetics to work in synergy with preservatives and to improve product stability. 11 September 2007 University of Idaho 4 EDTA – Modern Uses -http://en.wikipedia.org/wiki/EDTA Oil production: added into the borehole to inhibit mineral precipitation. Dairy and beverage industry: cleaning of bottles from milk stains. Flue gas cleaning: removal of NOx. Medicine: used in chelation therapy (brand name Endrate®, marketed by Hospira; generic product is also on the market) for acute hypercalcemia and mercury and has been used for lead poisoning. Added to many soft drinks containing ascorbic acid and sodium benzoate, to reduce the formation of benzene (a carcinogen). Can be used in the recovery of used lead acid batteries. Used in dentistry as a root canal irrigant to remove compounds of organic and inorganic debris (smearlayer). 11 September 2007 University of Idaho 5 Metal Complexes http://en.wikipedia.org/wiki/EDTA Agrochemicals: Fe, Zn and Cu fertilizer, especially in calcareous soils. Photography: use of Fe(III)EDTA as oxidizing agent. Scavenging metal ions: in biochemistry and molecular biology, ion depletion is commonly used to inactivate enzymes which could damage DNA or proteins 11 September 2007 University of Idaho 6 EDTA – Modern Uses http://www.dow.com/productsafety/images/edtachart.jpg 11 September 2007 University of Idaho 7 Complexation of Fe(II/III) with EDTA pKa1-6 = 0.0, 1.5, 2.0, 2.66, 6.16, 10.24 Kf(FeII) = 1014.32 Kf(FeIII) = 1025.1 11 September 2007 University of Idaho 8 Cyclic voltammetry - http://en.wikipedia.org/wiki/Cyclic_voltammetry red 0.7 volts ox Applied potential waveform to electrode ox + e- = red 11 September 2007 E0 = 0.7 volts University of Idaho 9 The Cyclic Voltammogram ox + e- red Start E End E ox + e- <-- red 11 September 2007 University of Idaho 10 Cyclic Voltammetry of Fe(II/III)EDTA 8.00E-06 1.0 mM FeIIIEDTA FeIIIEDTA + e- FeIIEDTA 6.00E-06 pH 7.40, 0.1 M HEPES buffer 10 mV/sec 4.00E-06 2.00E-06 Current (A) 0.00E+00 300 100 -100 -300 -500 -700 -2.00E-06 C disk electrode -4.00E-06 FeIIIEDTA + e- FeIIEDTA -6.00E-06 Potential (mV) 11 September 2007 University of Idaho 11 CV of Fe(II/III)EDTA in the presence of O2 Electrocatalytic (EC’) Voltammetry 2 Figure 1. Cyclic voltammetric curves on a pH =3 sample A 1.5 1 uA A) 0.1 mM FeIIIEDTA, air saturated B) 0.1 mM FeIIIEDTA only, N2 purged 0.5 B B 0 -0.5 0.3 0.2 0.1 scan rate = 5 mV/s. 11 September 2007 0 -0.1 -0.2 -0.3 -0.4 V University of Idaho 12 The reducing current is amplified and oxidizing current is absent in EC’ mechanism Electrochemical reduction coupled with a homogeneous reaction Fe EDTA e Fe EDTA III k' II 2 Fe EDTA O2 Fe EDTA O II 11 September 2007 k" University of Idaho III 13 Kinetic Realities FeIIIEDTA efast FeIIEDTA Electrode O2 eslow O2.- 11 September 2007 University of Idaho 14 Mediated Electron Transfer Catalytic Current Electrode e- FeIIIEDTA O2 fast FeIIEDTA 11 September 2007 University of Idaho fast O2.- 15 The Fenton Reaction FeIIIEDTA + e- = FeIIEDTA FeIIEDTA + H2O2 = FeIIIEDTA + HO- + HO∙ (fast) H2O2 + e- = HO- + HO∙ (slow) 11 September 2007 University of Idaho 16 EC’ Voltammetry with the Fenton Reaction Mechanism 11 September 2007 University of Idaho 17 Summary of Voltammetry EC’ mechanisms of Fenton Reaction FeIIIEDTA + e- = FeIIEDTA FeIIEDTA + H2O2 = FeIIIEDTA + HO- + HO∙ Oxygen Reduction FeIIIEDTA + e- = FeIIEDTA FeIIEDTA + O2 = FeIIIEDTA + O2.- 11 September 2007 University of Idaho 18 Outline of Investigation I] Room Temperature and Pressure Combustion of Organic Pollutants and Nerve Agent Surrogates – The Search for a Green Oxidant II] A Detector for Peroxide-Based Explosives III] A Model for the Role of Calcium and Zinc in Biological Oxidations 11 September 2007 University of Idaho 19 The search for a “green” oxidant Problems with chlorine based bleaching methods. Prefer low temperature and pressures, energy savings Oxygen is the ultimate green oxidant. Oxygen is kinetically stable 11 September 2007 University of Idaho 20 Overall Goals of Our Green Oxidation Program The destruction or neutralization of xenobiotics, including nerve agents and chlorinated pesticides using green oxidation chemistry. Focus on non-biological oxygen activation to eliminate the need for tricky enzyme based systems 11 September 2007 University of Idaho 21 Molecular Oxygen O2 is kinetically stable Oxygen’s two unpaired electrons make it difficult to accept a bonding pair Partially reduced oxygen 11 September 2007 University of Idaho 22 Reactive Oxygen Forms •O=O• b.o. = 2 120 kcal/mol +e- •O-O• b.o. = 1.5 80 kcal/mol G +4e+4H+ +2e+2H+ HO-OH b.o. = 1 50 kcal/mol 2H2O 11 September 2007 University of Idaho 23 Molecular Oxygen as a Facile Oxidant superoxide radical + e- hydrogen peroxide •- + eO2 H2O2 hydroxyl radical + e- HO + e- O2 H2O - e- - e- •- O2 - e- H2O2 - e- HO •Diagram showing reaction oxygen intermediates between O2 and H2O. •H+ left out for simplicity. 11 September 2007 University of Idaho 24 The Fenton Reaction H2O2 + e- HO• + HOFe(II) Fe(III) + eFe(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. 11 September 2007 University of Idaho 25 Oxygen Activation Biological cytochrome P450 enzymes, monooxygenase 11 September 2007 University of Idaho 26 Fe°, EDTA, Air (ZEA) system Fe(0), EDTA, & air The only nonbiological system known to date that can activate O2 under RTP and produce a facile oxidizing species capable of extensively degrading xenobiotics Organophosphorous agents Halocarbons Organics IF Cheng, et al, Ind. & Eng. Chem. Res. 2003, 42(21), 5024-5030. 11 September 2007 University of Idaho 27 Zero-Valent Iron Remediation of Halocarbons Iron as a reducing agent for halogenated organics Fe(0) + R-X + H2O Fe2+ + R-H + OH- + XCl x Cl CCl 3 Cly 11 September 2007 Cl University of Idaho 28 Appearance of oxidation products Fe(0) + R-X + H2O Fe2+ + R-H + OH- + X- Oxidized Hydrocarbons/LMW carboxylates 11 September 2007 University of Idaho 29 Fe°, EDTA, Air (ZEA) system III O2 Fe EDTA Fe 0 - e .- .- O2 + O2 + 2H+ II Fe EDTA 2+ Fe + EDTA II Fe EDTA 11 September 2007 + H2O2 III - Fe EDTA + HO University of Idaho + HO· 30 Outline of ZEA Research Introduction General Reaction Scheme Environmental Impact of EDTA The RTP Dioxygen Activation Zero-valent iron/EDTA/air (ZEA) system Degradation Kinetics and Reaction Products EDTA Mechanisms 11 September 2007 Chlorinated phenols Organophosphorus and UXO compounds Rate-limiting Step Conclusions University of Idaho 31 Concerns about EDTA Many industrial chelating agents are not degradable by methods currently found in wastewater treatment facilities Not readily biodegradable Considerable quantities of EDTA pass through wastewater treatment facilities in the form of FeIIIEDTA, as high as 18µM. Sillanpaa, Mika; Orma, Marjatt; Ramo, Jaakko; Oikair; “The importance of ligand speciation in environmental research: a case study”; The Science of the Total Environment; 2001; 267, 2331. Sillanpaa, M; Pirkanniemi, K.; “Recent Developments in Chelate Degradation”; Environmental Technology, 2001, 22, 791. Kari, F. G.; Giger W; Modeling the Photochemical Degradation of Ethylenediaminetetraacetate in the River Glatt; Environmental Science and Technology; 1995, 29, 2814. Nirel, P. et. al.; Method for EDTA Speciation Deteremination: Application to Sewage Treatment Plant Effluents; Wat. Res; 1998; 32, 3615. Kari, F. G. and Giger W.; Speciation and fate of EDTA in municipal wasterwater treatment. Wat. Res., 1996, 30, 122-134. 11 September 2007 University of Idaho 32 Concerns about EDTA Questions regarding the ability to mobilize metals in the environment. Currently not being monitored or treated at waste water treatment facilities Concern for heavy metal mobility and longer bioavailability of metals to aquatic plants and animals Stable in aquatic environment EDTA is anthropogenic and long-lived. 11 September 2007 University of Idaho 33 Goals •The destruction or neutralization of EDTA (xenobiotics) •Search for in situ conditions that will aid in the reduction in the release of EDTA in emerging green chemistries. Inexpensive & Safe Processes. •Room Temperature and Pressure Conditions (RTP) •Common Reagents – Long Term Storage •No Specialized Catalysts •System that may be incorporated into existing water treatment systems 11 September 2007 University of Idaho 34 Experimental Setup 1 mM EDTA (Total Vol. 50mL) 2.5g Fe° 30-40 mesh Aldrich Open to the Atmosphere 125 ml round bottom flask Aliquots were taken directly from reaction vessel, diluted, filtered and injected into HPLC stir bar 2.5 g Fe° 11 September 2007 Bioanalytical Systems – RPM controlled stir plate University of Idaho 35 Visual Detection of H2O2 Produced by ZEA System [HCl] = 0.04 M [ammonium molybdate] = 0.08 mM [KI] = 80 mM [EDTA] = 0 or 1.2 mM Agar (Starch) Proposed 2FeIIEDTA + O2 + 2H+ 2FeIIIEDTA + H2O2 H2O2 + 3I- +2H+ I3- + 2H2O I3- + starch blue-violet complex 11 September 2007 University of Idaho 36 Iron wire: EDTA Absent & starch reagents 11 September 2007 University of Idaho 37 Iron wire: EDTA Present 11 September 2007 University of Idaho 38 EDTA required for the ZEA reaction Qualitative Results Fe(0) + O2 + 2H+ Fe2+ + H2O2 Slow 2FeIIEDTA + O2 + 2H+ 2FeIIIEDTA + H2O2 Fast 11 September 2007 University of Idaho 39 Evidence for Production of Reactive Oxygen Species I: Heterogeneous O2 Activation O2 e- Fe ROS O2.- 0 + O2.- + 2H+ Fe2++ EDTA FeIIEDTA O2-•, H2O2, HO., FeIV=O, etc. + FeIIIEDTA H2O 2 - + HO + HO Two Analyses were performed Thiobarbituric acid-reactive substances (TBARS) assay Addition of known radical scavenger, 1-butanol II: Homogeneous O2 Activation FeIIIEDTA Fe0 O2 eFeIIEDTA O2.- H 2O 2 FeIIIEDTA + O2.- + 2H+ Fe2++ EDTA FeIIEDTA 11 September 2007 University of Idaho + - + HO + HO 40 Suppression of EDTA degradation with the addition of Radical Scavenger 1-butanol is a •OH radical scavenger -6.5 (■) kobs = -1.11 M-1hr-1 ln [Fe III EDTA] -7 -7.5 -8 Control (no Fe) -8.5 EDTA, Air -9 -9.5 5 mM 1-butanol -10 Linear ( EDTA, 4 Air) 5 6 Linear (5 mM 1butanol) 0 1 2 3 Time (hrs) (▲)kobs = -0.08 M-1hr-1 with 5mM 1-butanol (2.5 g ZVI g, 1.00mM EDTA, open to air) Mantzavinos D; Water Res. 2004 Jul;38(13):3110-8. J Hazard Mater. 2004 Apr 30;108(1-2):95-102. 11 September 2007 University of Idaho 41 Summary of ZEA system and O2 Both TBARS and butanol tests indicate that ZEA system is able to produce facile oxidant from air at RTP Rare form of abiotic O2 activation at RTP Identity of oxidant isn’t clear HO· FeIV=O 11 September 2007 University of Idaho 42 Degradation of EDTA by ZEA reaction COOH HN COOH HOOC N HOOC COOH N COOH 1 mM EDTA (50mL, aqueous) 2.5g Fe° + air 11 September 2007 COOH University of Idaho HOOC COOH CO2/HCO3- 43 Carbon Balance - Total Organic Carbon*, ESI-MS**, HPLC# Table 1 : Carbon Balance 1mM EDTA, 2.5g ZVI, air, reaction volume 50mL, 6hrs %C CO2 35% (± 5)* Iminodiacetic Acid 28% (± 3)** Oxalic acid 17% (± 2)** Propionic Acid 14 % (± 2)** EDTA 2% (± 2)# Total 96% Trapping of the volatile gases using Tenax® showed no volatile organic carbon of molecular weight C4 and above released from the system during the course of the reaction 11 September 2007 University of Idaho 44 Products of ZEA System None of the products of EDTA are significant metal chelation agents. All are more easily biodegraded. The ZEA system has proven successful at the degradation of other organic xenobiotics. 11 September 2007 Halocarbons Organophosphorus Organics University of Idaho 45 Organophosphorous Nerve Agents and Nitrated Explosive Surrogates TNT surrogate, nitrobenzene (985 ppm) was decomposed in 24 hours. VX surrogate, malathion (49 ppm) was consumed in 4 hours, to give diethyl succinate. Malathion was the only pollutant to give a byproduct detectable by GC-FID. H3C O CH3 O + + H3C O O H3C H3C CH3 N N O O O O- O- -O + N CH3 O P N CH3 + S S N S O -O VX O P CH3 TNT O H3C O CH3 nitrobenzene malathion 11 September 2007 University of Idaho 46 Malathion Degradation DES H3C malathion O O H3C H3C O CH3 O O max: 4-6 hrs O O O CH3 S O S P O O H3C O CH3 CH3 S O P O O H3C O O PO43- + SO42H3C SO42- :0.0593mM (14% yield) (24hrs) PO42- : 0.0825 mM (19 % yield) (24hrs) 11 September 2007 University of Idaho malaoxon Max: 7 hrs 47 Kinetics of Malathion Degradation Malathion Diethyl Succinate (DES) GC/FID chromatograph: each data point indicates an individual reaction vial extracted using 50/50 hexane/ethyl acetate, error bars indicate the standard deviation between three measurements of each sample vial. 11 September 2007 University of Idaho 48 Kinetically stable organic products from ZEA degradation. iminodiacetic acid (degrades after 12 hrs) propionic acid Degradation products for 11 September 2007 bicarbonate succinic acid Oxalic acid -EDTA -Malathion -4-chlorophenol -pentachlorophenol -phenol University of Idaho 49 Overall Scheme (simplified) This study Beenackers Ing. Eng. Chem. Res. 1992, 32, 2580 Van Eldik Inorg. Chem, 1997, 36, 4115-4120 25.5 kJ/mol 27.2 kJ/mol 33.9 kJ/mol Metal dissolution: Fe(0) Fe2+ + 2e- (1) Complex formation Fe2+ + EDTA FeIIEDTA (2) Homogeneous O2 activation: 2FeIIEDTA + O2 + 2H+ 2FeIIIEDTA + H2O2 (3) Fenton Reaction FeIIEDTA + H2O2 FeIIIEDTA + OH• + OH- (4) EDTA degradation: OH• + FeEDTA Fe2+/3+ + EDTA* (5) EDTA* = damaged EDTA Redox Cycling: FeIIIEDTA + e- FeIIEDTA (6) •Step 3 is Rate-Limiting 11 September 2007 University of Idaho 50 Voltammetric Studies ZEA reaction rate is dependent on pH 2.5 < pH < 4.5 LMW Acids Self Buffers the ZEA reaction at 3.5 Oxygen Activation Rates Measured By Cyclic Voltammetry 11 September 2007 University of Idaho 51 CV of Fe(II/III)EDTA in the presence of O2 Electrocatalytic (EC’) Voltammetry 2 Figure 1. Cyclic voltammetric curves on a pH =3 sample A 1.5 A) 0.1 mM FeIIIEDTA and O2 saturated, B) 0.1 mM FeIIIEDTA only, uA 1 0.5 B B 0 -0.5 0.3 0.2 0.1 scan rate = 5 mV/s. 11 September 2007 0 -0.1 -0.2 -0.3 -0.4 V University of Idaho 52 Electrocatalytic currents at -200mV at 5mV/s. Current vs pH Current(uA) 1.2000 1.0000 0.8000 0.6000 0.4000 0.2000 0.0000 0 2 4 6 8 10 12 pH 11 September 2007 University of Idaho 53 2.5 < pH < 4.5 Current vs pH Current(uA) 1.2000 1.0000 0.8000 0.6000 0.4000 0.2000 0.0000 0 2 4 6 8 10 12 pH molar fraction b Free Fe2+ 1.00 0.90 0.80 0.70 0.60 0.50 0.40 0.30 0.20 0.10 0.00 FeIIEDTA FeII(OH)2EDTA FeII(OH)EDTA FeIIH 0 FeIIHEDTA (MLH) 2EDTA 2 4 6 8 10 12 14 pH 11 September 2007 University of Idaho 54 Fe(II)HEDTA or MLH is responsible for oxygen activation N N N Fe N Fe I 11 September 2007 II COOH N N Fe COOH HOOC O2 COOH N HOOC N COOH III University of Idaho 55 ZEA Reaction - Conclusions This system is a viable option for the destruction of a variety of pollutants and has a strong possibility for scale up. The only system known to date that can obtain non-biological Oxygen Activation at room temperature and pressure to produce reactive oxygen species that are capable of fully degrading pollutants to LMW carboxylates and inorganic forms Due to the duality of EDTA acting as both a pro-oxidant and antioxidant, controlling the [EDTA] is imperative to the success of the process. Rate-limiting steps is (are) oxygen activation FeIIEDTA may provide insights into biological oxygen activation 11 September 2007 University of Idaho 56 Detector for Triacetone Triperoxide Wikipedia http://en.wikipedia.org/wiki/Acetone_peroxide Acetone peroxide (triacetone triperoxide, peroxyacetone, TATP, TCAP) is an organic peroxide and a primary high explosive. 11 September 2007 University of Idaho 57 TATP Detector Outline Background Need for Detection Systems Dangers Recent News Fast Field Portable (handheld) Selective and LOD Electrochemical Detection Via Fenton Rxn 11 September 2007 University of Idaho 58 TATP – 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 11 September 2007 University of Idaho 59 TATP – Ease of Synthesis 3H2O2 + 3CH3COCH3= ((CH3)2COO)3 + 3H2O Ice Bath 3% H2O2 (30% or more preferable) Acetone (paint thinner) H2SO4 (battery acid) 11 September 2007 University of Idaho 60 TATP – physiochemical characteristics Shock Sensitive Heat Sensitive High V.P. 7 Pa @ 300K* 66% weight loss within 2 weeks at room temperature** No Possible Commercial or Military Applications *Propellants, Explosives, Pyrotechnics 30 (2005)127 **J. Am. Chem. Soc. 2005, 127, 1146-1159 11 September 2007 University of Idaho 61 TATP is suicide bombers' weapon of choice Times (London) July 15, 2005 By Philippe Naughton Rediscovered in the West Bank (Israel) in the early 1980s and soon became an extremists' staple. Suicide Bombers – “Mother of Satan” But as the Palestinian bomb-makers will attest - 40 Palestinians are thought to have been killed making or handling the explosive - it is highly unstable and sensitive to heat and friction. 11 September 2007 University of Idaho 62 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. 11 September 2007 University of Idaho 63 TATP – 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 September 2007 University of Idaho 64 TATP – Shoe Bomber http://www.univie.ac.at/cga/art/shoe_bomb3.gif 11 September 2007 University of Idaho 65 TATP – Domestic Terrorists http://www.koco.com/news/ 5058347/detail.html Sources Identify TATP As Component Of Bomb TATP Same Component Used By Infamous Shoe Bomber POSTED: 9:56 pm CDT October 4, 2005 UPDATED: 10:11 pm CDT October 4, 2005 NORMAN, Okla. -Sources confirmed Tuesday night that at least one of the components in the bomb used by Joel Henry Hinrichs III Saturday night was a product called TATP. 11 September 2007 University of Idaho 66 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, QUARTSIZE, 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/ 11 September 2007 University of Idaho 67 TATP Detection the Challenge The Need for a Fast Portable Detector Innocuous Appearing White Powder Despite a high VP Cannot be Sensed by Dogs Lacks Chromophoric Groups (not detectable by UV-vis absorbance) 11 September 2007 University of Idaho 68 TATP – Detector Requirements Unknown Materials – Public Safety, e.g. Airports Air Samples, e.g. Airports Moderate Selectivity– Low Limits of Detection Required Debris at Post-Explosion Sites High Selectivity – Low Limits of Detection not Required 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. 386 559-565 (2006) 11 September 2007 University of Idaho 69 TATP - Detector IR-Raman Fluorescence/UV-vis Absorbance Low LOD requires tagging Ion Mobility High Selectivity – Relatively High LOD Good Selectivity, moderate LOD HPLC or GC Excellent Selectivity and LOD 11 September 2007 University of Idaho 70 TATP – State of Detectors Costs Lack of Field Portability Ideal – Handheld Sensor May Require Knowledgeable User e.g. Commercial Glucose Sensors 11 September 2007 University of Idaho 71 Glucose Sensors - www.edaq.com/teachapp3.html 11 September 2007 University of Idaho 72 DC Harris, Quantitative Chemical Analysis 6th ed. Chapter 17 11 September 2007 University of Idaho 73 TATP – Detection by Electrochemical Means Proposed Basis For Detection Fenton Reaction for Organic Peroxides RO-OR + FeIIEDTA RO- + RO· + FeIIIEDTA 11 September 2007 University of Idaho 74 TATP – Electrochemical Detection Reaction with Organic Peroxides is not Spontaneous RO-OR + FeIIEDTA N.R. RO-OR + e- RO- + RO· FeIIEDTA FeIIIEDTA + eEcell = Ecath – Eanod 11 September 2007 E0 <-0.5 V 0.1 V -0.6 V University of Idaho 75 TATP – Electrochemical Detection Reaction with Peroxides and Hydroperoxides is Spontaneous RO-OH + e- RO- + HO· HO-OH + e- HO- + HO· E0 ≈0.4 V 0.8 V FeIIEDTA + RO-OH/HO-OH FeIIIEDTA + RO∙/HO∙/H+ Requires that TATP be degraded 11 September 2007 University of Idaho 76 TATP – Degradation to HOOH/ROOH Acid degradation TATP + H+ H2O2 + Products Conc. [HCl] 10 minutes 11 September 2007 University of Idaho 77 TATP – Cyclic Voltammograms after Acid Digestion 0.07 A 0.06 Current (mA) 0.05 0.04 0.03 0.02 0.01 B 0 -0.01 100 0 -100 -200 -300 -400 -500 Potential (mV) Figure 1. Cyclic voltammograms of two solutions both containing 10 mM TATP and 1 mM FeIIIEDTA under dearated conditions, 30 mV/s. A) Acid treated TATP. B) Non-acid treated TATP. 11 September 2007 University of Idaho 78 TATP – Chronoamperometric Detection Simpler and Faster than Cyclic Voltammetry Basis of the Glucose Sensor E E E0 0 11 September 2007 0.0592 [red ] log n [ox] time University of Idaho 79 TATP - 4 3 E 0.0592 [red ] EE log n [ox] 2 0 1 1/ 2 nFAD C i 1 / 2t 1 / 2 b 0 time 4 3 i 2 1 0 11 September 2007 University of Idaho time 80 0.025 0.023 Current (mA) 0.021 0.019 0.017 A 0.015 B 0.013 0.0 20.0 40.0 60.0 80.0 100.0 120.0 140.0 Time (s) Figure 3. Current-time measurements of a glassy carbon transducer in 1 mM FeIIIEDTA. A) 0.04 mM acid treated TATP, B) Background with no TATP. 11 September 2007 University of Idaho 81 0.04 0.035 y = 0.025x + 4E-05 R2 = 0.9999 Current (mA) 0.03 0.025 0.02 0.015 0.01 0.005 0 0 0.2 0.4 0.6 0.8 1 1.2 1.4 1.6 [TATP] mM Figure 4. TATP calibration curve. The slope provides a sensitivity of 0.025 mA/mM TATP. The detection limit was found to be 0.886 μM. Error bars indicate one standard deviation. 11 September 2007 University of Idaho 82 Conclusions – Chronoamperometric TATP Detection 0.886 µM LOD O2 interference FeIIEDTA + O2 FeIIIEDTA + O2.FeIIEDTA + HO-OH FeIIIEDTA + HO∙ + HO- Requires Acid Pretreatment 10 min. Sample Pretreatment 11 September 2007 University of Idaho 83 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 11 September 2007 University of Idaho 84 Acknowledgements Derek Laine Funding NIH Kenichi Shimizu NSF Simon McAllister NSF-SGER Ruhba Ponraj Mark D. Engelmann, Ph.D. 2003 Tina Noradoun, Ph.D. 2005 Ryan Hutcheson, B.S. 2004 NASA EPRI BLM UI Rob Bobier, B.S. 2002 Terry Hiatt, B.S. 2000 11 September 2007 University of Idaho 85 11 September 2007 University of Idaho 86 Reactive Oxygen Species (ROS) in Biology 11 September 2007 University of Idaho 87 ROS and Inflammation Phagocytes Infections -viruses -bacteria -parasites Foreign Substances -smoke -asbestos Damaged Tissue -heat -mechanical -UV 11 September 2007 Activation of Inflammatory Cells University of Idaho ROS RNS 88 ROS and Inflammation ClO2.H2O2 NO. 11 September 2007 University of Idaho HOCl + Ca2+ ONOO.- 89 Iron Enzymes and the Fenton Reaction Hemes/Cytochromes Oxygenases Oxidases H2O2 + reducing agent HO. •All Fe-containing enzymes are quite good Fenton Reaction agents. •Oxidative Stress 11 September 2007 University of Idaho 90 11 September 2007 University of Idaho 91 Inflammation The Good Inflammation protects the body •Destroys invading pathogens •Dissolves damaged tissue The Bad Chronic or prolong inflammation Allergies and Autoimmune Diseases •All the many types of allergies •Many of the autoimmune diseases 11 September 2007 University of Idaho 92 Role of Calcium in Inflammation 11 September 2007 University of Idaho 93 Role of Calcium in Inflammation Enhances Oxidative Processes in Inflammation ROS Paradoxically Redox Inactive, i.e. always Ca2+ Inflammation { H2O2 O2.- Ca2+ Role in Biological Oxidations Not Well Understood 11 September 2007 University of Idaho 94 Inflammation Sequence FeII apoenzyme HO· ROS Inflammation { H2O2 Cl- HOCl FeIIenzyme O2.- NO ONOOCa2+ ? 11 September 2007 University of Idaho 95 The Low MW Iron Pool FeII apoenzyme HO· ROS Inflammation { H2O2 Cl- HOCl FeIIenzyme O2.NO ONOO- Ca2+ ? Fe Fe released into LMW pool ROS 11 September 2007 University of Idaho 96 Ligands for the LMW Fe pool Glutamate Citrate Phosphates, e.g. ATP, ADP, GTP, etc. Amino Acids Peptides Proteins (HMW) 11 September 2007 University of Idaho 97 Fe(II/III)EDTA as a model for physiological LMW Fe 11 September 2007 University of Idaho 98 The concentration ratio of [Chelate/Ligand]:[Fe] is very high Physiological Concentration Mobile (Free) Iron ≈ 10-9 M [Chelates/Ligand] ≈ 10-3 M Does this have any effect of the reactivity of LMW-Fe in the Fenton Rxn? 11 September 2007 University of Idaho 99 11 September 2007 University of Idaho 100 FeII/IIIEDTA CV in [Fe]:[EDTA] at 1:10 and 1:1 11 September 2007 University of Idaho 101 EC’ CV of FeII/IIIEDTA (1:1) with H2O2 FeIIIEDTA + e- = FeIIEDTA FeIIEDTA + H2O2 = FeIIIEDTA + HO- + HO∙ (fast) H2O2 + e- = HO- + HO∙ (slow) 11 September 2007 University of Idaho 102 EC’ current measured at -700 mV various ratios of [Fe]:[Ligand] 11 September 2007 University of Idaho 103 Excess molar EDTA and other Chelates suppress Fenton Rxn kinetics = 102-104 FeII-OOH(EDTA) (see references below) FeII-OOH(EDTA) + Excess EDTA FeII(EDTA) + HOOH V. Zang, R. van Eldik “Kinetics and Mechanism of the Autoxidation of Iron(II) Induced through Chelation by Ethylenediaminetetracetate and Related Ligands” Inorganic Chemistry 1990, 29, 1705-1711. Ariane Brausam, Rudi van Eldik “Further Mechanistic Information on the Reaction Bewteen FeIIIEDTA and Hydrogen Peroxide: Observations of a Second Reaction Step and Importance of pH” Inorganic Chemistry, 2004, 43, 5351-5359. [1] Walling, C., Kurz, M., Schugar, H.J. 1970 “The Iron(III)-Ethylenediaminetetraacetic Acid-Peroxide System” Inorganic Chemistry, 9(4), 931-937 11 September 2007 University of Idaho 104 Hypothesized Role of Calcium in Inflammation 11 September 2007 University of Idaho 105 Ca2+ increases Fenton Rxn Kinetics in high [EDTA]:[Fe] ratios Recovery of Fenton reactivity of Fe complexes by addition of Ca2+. 1:50 [FeIII]:[citrate] 1:20 [FeIII]:[NTA] 1:10 [FeIII]:[EDTA] EDTA Citrate NTA Other common conditions: 0.1 mM Fe3+, 22.8 mM H2O2, and pH 7.4 HEPES, carbon disk electrode, 10 mV/s sweep rate 0 0.3 0.5 0.7 1 2 5 10 Ca:L ratio 11 September 2007 University of Idaho 106 Table 1: Stability Constants for M:L complexes Log β1 Ca+2 Fe+2 Fe+3 Ethylenediaminetetraacetic Acid (EDTA) (HOOCCH2)2NCH2CH2N(CH2COOH)2 10.65 14.32 25.1 Nitrilotriacetic Acid (NTA) (HOOCCH2)3N 6.3 8.9 15.9 Citric Acid HOOCCH2CH(OH)(COOH)-CH2COOH 3.45 4.4 11.5 •Ca2+ uptakes excess metal binding capacity without displacing FeII or FeIII •Optimizes FeIIEDTA to the 1:1 molar ratio form 11 September 2007 University of Idaho 107 FeII apoenzyme HO· ROS Inflammation { H2O2 Cl- HOCl FeIIenzyme O2.NO ONOO- Ca2+ High [L]:[FeII] Oxidatively inactive Fe released into LMW pool Ca2+ optimized [L]:[FeII] Oxidatively active 11 September 2007 University of Idaho 108 FeII apoenzyme HO· ROS { Inflammation H2O2 Cl- FeIIenzyme HOCl O2.- Fe released into LMW pool NO ONOOHigh [L]:[FeII] inactive Ca2+ redox cycling H2O2 HO· Damage to DNA Lipids Proteins optimized [L]:[FeII] active 11 September 2007 University of Idaho 109 Conclusions II FeII/IIIEDTA is a good model for LMW physiological iron Ca2+ part of the inflammation cascade to optimize Fe chelation sphere for the Fenton Rxn. 11 September 2007 University of Idaho 110 Other studies using FeEDTA Sensor for Peroxide Based Explosives O2 reduction catalysts for fuel cells 11 September 2007 University of Idaho 111 Acknowledgements Derek Laine Funding NIH Kenichi Shimizu NSF Simon McAllister NASA Ruhba Ponraj Mark D. Engelmann, Ph.D. 2003 Tina Noradoun, Ph.D. 2005 Ryan Hutcheson, B.S. 2004 EPRI BLM UI Rob Bobier, B.S. 2002 Terry Hiatt, B.S. 2000 11 September 2007 University of Idaho 112 http://www.moscow.com/ 11 September 2007 University of Idaho 113 11 September 2007 University of Idaho 114 www.latahrealty.com/ 11 September 2007 University of Idaho 115 11 September 2007 University of Idaho 116 Visit Our Web Site! www.chem.uidaho.edu 11 September 2007 University of Idaho 117 UI Stipend goes along way in Moscow, Idaho TA+Renfrew Scholarship 12 months $18,800 Effective Fees -$1,940 Health Insurance -$1,200 Average One Bedroom Apt $350-550 Average Two Bedroom Apt $450-650 11 September 2007 University of Idaho 118