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DART and Trace Evidence (a bag of tricks for using DART)

DART and Trace Evidence (a bag of tricks for using DART). Robert B. Cody JEOL USA, Inc. . Outline. Use of dopants with DART SPME, other methods for analyzing volatiles Derivatization and H/D Exchange Counterfeit materials Quantitative analysis Pyrolysis of polymers, materials

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DART and Trace Evidence (a bag of tricks for using DART)

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  1. DART and Trace Evidence(a bag of tricks for using DART) Robert B. Cody JEOL USA, Inc.

  2. Outline • Use of dopants with DART • SPME, other methods for analyzing volatiles • Derivatization and H/D Exchange • Counterfeit materials • Quantitative analysis • Pyrolysis of polymers, materials • Other DART chemistries • Atmospheric pressure thermal ionization for inorganics

  3. Dopants, adducts Some compounds don’t form MH+ or [M-H]- Ammonia, NH4OH useful for forming [M+NH4]+ from polar analytes that will not form MH+ Carbonyls, peroxides Chloride, acetate, nitrate useful for forming anion adducts for compounds that will not form [M-H]- e.g. [M+Cl]- from explosives like RDX, PETN

  4. Dopant addition NH4OH, MeCl2 on swab Sample DART or liquid in vial with capillary into gas stream…or…

  5. Example: Organic acids (e.g. aspirin) Should normally be analyzed in negative ion mode: give abundant [M-H]- Will not normally form [M+H]+ However, can form [M+H]+ and [M+NH4]+ if ammonium is present

  6. Example: Aspirin

  7. Explosives

  8. Explosives detected on wipe Name Neutral comp. Meas. Calc. Diff(u) Rel. Abund. TNT-H C7H5N3O6 226.0125 226.0100 0.0025 100.0000 HMX+Cl C4H8N8O8 331.0164 331.0154 0.0010 59.6984 RDX+Cl C3H6N6O6 257.0078 257.0037 0.0041 39.5938 PETN+Cl C5H8N4O12 350.9821 350.9827 -0.0006 14.8834 amino-DNT+Cl C7H7N3O4 232.0149 232.0125 0.0024 10.7766 Tetryl+Cl C7H5N5O8 321.9839 321.9826 0.0012 3.8259 NG+Cl C3H5N3O9 261.9713 261.9714 -0.0001 2.2762 PETN-H C5H8N4O12 315.0101 315.0060 0.0041 1.8731

  9. Nitroglycerin on an employee’s tie 8 hours after walking through plume from construction blasting x 10 NO3- C3H5O3- MCl- NO2- 50 100 150 200 250 300 350 m/z

  10. Volatiles, headspace: some applications • Arson accelerants • Residual solvent vapors • Odors • Liquors • Residual tear gas ?

  11. Volatiles, headspace: methods 1. Direct analysis 2. Adsorbant (e.g. Tenax), thermal desorption 3. Solid-phase microextraction

  12. 50 100 150 200 250 300 350 400 450 m/z 50 100 150 200 250 300 350 400 450 m/z 50 100 150 200 250 300 350 400 450 m/z 1. Volatiles, headspace: direct Diesel fuel standard Carpet burned with diesel Burnt carpet (no accelerant) Scale x50

  13. Direct analysis of volatiles • Fast and easy, but may not be best choice in looking for trace components in presence of strong interference • Concentrate the vapor (adsorbent) • Concentrate and select the sample (SPME)

  14. 2. Volatiles, headspace: trap • Adsorbant, thermal desorption • Trap vapor on Tenax, heat to desorb and purge with inert gas • or place sample inside thermal desorption chamber Inject sample with gas-tight syringe Adsorbant in heatable trap to DART He

  15. 3. Volatiles, headspace: SPME • Fiber coated with extractive phase (e.g. PDMS) • Selective phases • Compatible with GC/MS, DART, LC/MS

  16. SPME/DART Procedure We have had good success with DVB/Carboxen/PDMS SPME fibers (Supelco) 1. Clean SPME fiber: heat to 250 degrees C in inert gas (e.g. GC injector) 3. Hold fiber in DART gas stream (250 degrees C) 2. Expose SPME fiber to headspace or liquid solution for several minutes

  17. Prep: SPME/DART Irish whiskey EtOH dimer 93.0900 100 80 60 Rel. Abund. 40 20 0 60 120 180 240 Carboxen/DVB/PDMS SPME Fiber 100 Et-octanoate 80 93.0917 Et-decanoate 60 173.1521 Rel. Abund. 40 201.1875 Et-hexanoate 20 Furfural Et-dodecanoate 0 60 120 180 240 m/z Direct: No SPME

  18. Derivatization and reactions • Derivatize to enhance volatility, count and protect labile groups like OH • Use rapid derivatization, no further cleanup • H/D exchange to count exchangeable H’s • Provides some structural information • Distinguish some isomers

  19. Polyhydroxy compoundsDerivatization with TMSI/Pyridine Commercially available e.g. Pierce Tri-Sil-ZR Simple, rapid silylation reaction. Mix with sample and heat for a few seconds (heat gun). Moisture-tolerant (use excess reagent) Count the OH’s. Only reacts with hydroxyl groups. Unreactive with thiol, amine groups. Mix, heat, analyze. No purification step needed.

  20. g-Cyclodextrin [g-CD+TMSn+C3H5N2]+ 100 % n=22 n=23 C48H80O40 Underivatized MW 1296.4 8 amyloses 24 hydroxyls 24 TMS’s Rel. Abundance n=21 n=20 n=24 n=19 2549 2619 2689 2759 2829 2899 2969 3039 3109 3179 m/z

  21. Aminoglycoside antibiotics n = 7 n = 6 n = 8 n = 5 950 1000 1050 1100 1150 1200 1250 m/z [M+TMSn+H]+ See 1 extra (small) TMS for these compounds Neomycin sulfate C23H46N6O13. 3H2SO4 Neomycin sulfate: 7 OH’s, see 8 TMS’s Kanamycin B sulfate: 6 OH’s, see 7 TMS’s Apramycin sulfate: 6 OH’s, see 7 TMS’s

  22. Melamine detected in pet food by Teresa Vail (University of the Pacific) 127.072 Melamine C3H6N6 MH+ = 127.073 6 exchangeable H’s

  23. Melamine H/D Exchange 7: [D6-melamine+D]+ Melamine: with D2O 6 5 3 4 1 2 Melamine: No D2O MH+ C3H6N6

  24. BT (Bacillus Thuringensis) SporesGarden Pest Control Spore Biomarker MH+ Dipicolinic acid dimethyl ester DART+ / He Heated with TMAH

  25. Counterfeit materials • Presence or absence of critical ingredients (e.g. active pharmaceutical ingredients) • Differences in the presence or absence of trace impurities

  26. Genuine and Counterfeit CialisTabletsCourtesy Tony Moffat (U. London Pharmacy) Tadalafil (Cialis) Genuine Other tablet components Sildenafil (Viagra) Counterfeit

  27. Counterfeit Antimalarials “Yaa-chud” (Combination medicine) Samples from Prof. Facundo Fernandez Georgia Tech All these and more were analyzed in a single afternoon. Most of the time was taken up by opening the packages and keeping track of sample serial numbers.

  28. Counterfeit Antimalarials were found to contain: Chlorpheniramine (antihistamine) Acetaminophen (analgesic) Chloroquin (older, ineffective antimalarial) Aspirin (analgesic) Chloramphenicol (antibacterial) Pyramethamine/sulfadoxin (ineffective in SE Asia) Metamizol (analgesic, may cause bone marrow disorders) Some tablets contained low levels of the active ingredient (artemisinin), presumably to fool the field tests

  29. Real (top) vs. Counterfeit Marlboro Brand Cigarette Volatiletrace components are different Nicotine

  30. DART Quantitation Successful for liquid samples Internal standard corrects for variations in sample positioning. Example: GHB in urine Possibility for AWC analysis without I.S. ? Some fully validated methods completed Semiquantitative data obtained from swabs with no internal standard Under investigation for solid samples (tablets). Preliminary data promising

  31. AutoDART: Promazine (Chlorpromazine I.S.) 5 replicates, 7 concentrations, 250 ppb to 250 ppm, CV = 4.5% Linear fit

  32. Enhanced Ion Collection with Vacuum Pump Orifice DART Tube Pump IonSense GIST ImplementationReported BMSS 9/07 GIST on AccuTOF

  33. AutoDART + GIST: Lower detection limitsChlorpromazine (Promazine I.S.) CV = 5.7% 10 replicates 100 ppb Log/log plot, 6 replicates over 2 day period, 0.1 ppb to 1000 ppb

  34. IonSense VapurTM Pro’s and Con’s • Reduced helium consumption • Better quantitative reproducibility • Better detection limits for compounds with high proton affinities (stable ions in atmosphere). This includes most drugs and many compounds of forensic interest. • Poorer detection limits for compounds, with lower proton affinities e.g. methyl stearate • Cannot adjust DART chemistry to analyze hydrocarbons, produce odd-electron ions.

  35. Another kind of information: Products are a mixture of components Each component adds a detail to a characteristic “fingerprint” pattern DART mass spectrum Pattern matching for materials, commercial products, polymers, adhesives, etc.

  36. Polymers Nylon 6 poly(caprolactam) Polyethylene terephthalate

  37. PittCon Carpet 2006

  38. PittCon Carpet Polymer = Nylon 6 Match: Nylon 6

  39. Material ID: Latex from J&J Band-Aid 279.1612 C16H23O4+ 345.3535 C25H45+ 413.4145 C30H53+ 277.2906 C20H37+ 481.4807 C35H61+ 551.5575 C40H71+ 619.6162 C45H79+ • Searchable polymer library spectrum • All compositions confirmed by exact masses • C5H8 (isoprene) units • m/z 279=Dibutyl phthalate (plasticizer)

  40. 3 beige paint chips • Different beige paints give different mass spectra • Spectra are reproducible and a searchable library can be created • Polymers and additives can be identified.

  41. Condom lubricants Condom swab Post-coital vaginal swab

  42. CS (Tear gas) Detected Directly on Cloth 189.0209 [M+H]+ 207.0311 [M+H+H2O]+ 377.0348 [2M+H]+ 100 200 300 400 500 m / z 2-Chlorobenzalmalononitrile CAS # 2698-41-1 Formula: C10H5ClN2

  43. Other DART CI Reagents Values from http://webbook.nist.gov

  44. Proton transfer is very useful, but it is not universal Won’t work for saturated alkanes and some other compounds Even-electron ions Can we produce odd-electron ions and mass spectra that resemble EI mass spectra?

  45. Different DART Chemistries O2+. [(H2O)2+H]+ He DART O2+ Charge Exchange 100 [(H2O)3+H]+ 80 60 40 Rel. Abund. 20 0 15 20 25 30 35 40 45 50 55 NO+. [(H2O)2+H]+ 100 [(H2O)+NH3+H]+ 80 NH4+ 60 Rel. Abund. [NO+NH3+H]+ 40 N2H+ H3O+ 20 0 20 25 30 35 40 45 m/z Charge exchange H3O+ Addition, charge exchange, hydride abstraction, oxidation N2 DART NO+ APCI

  46. Charge-Exchange DART Oxygen He* + O2→ O2+. + e- + He O2+. + S → S+. + O2 O2 +. + S → Fragment++ O2 + R. (IE of sample S < 12.07 eV) Fluorobenzene He* + C6H5F → C6H5F+. + e- + He C6H5F+. + S → S+. + C6H5F C6H5F+. + S → [Fragment]++ C6H5F+ R. (IE of sample S < 9.2 eV)

  47. n-Hexadecane Normal DART Parameters [M-H+O]+ [M-H]+ [M-3H+2O]+ DART O2+. Charge Exchange M+. Electron ionization

  48. Hexadecane : Fragmentation vs. temperature Helium 200 degrees Helium 300 degrees

  49. Cholesterol 369.3528 100 [M+H-H2O]+ 50 Rel. Abund. Normal DART: Proton Transfer 385.3437 [M-H]+ 0 300 325 350 375 400 425 369.3529 100 386.3551 Fluorobenzene Dopant 50 Rel. Abund. 369.3542 100 0 300 325 350 375 400 425 386.3558 50 Rel. Abund. 0 300 325 350 375 400 425 M+. m/z Oxygen Charge Exchange

  50. 8 6 3 9 12 13 5 11 1 2 4 10 7 GC-DART: Grob Mix TICs Modified DART parameters Pseudo EI spectra • 1,3-Butanediol • Decane • 1-Octanol • Undecane • Nonanal • 2,6-Dimethylphenol • 2-Ethylhexanoic acid • 2,6-Dimethylaniline • Methyl decanoate • Surfynol • Methyl undecenoate • Dicyclohexylamine • Methyl dodecanoate

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