Presentation on theme: "Technology Transition Workshop DART and Trace Evidence (a bag of tricks for using DART) Robert B. Cody JEOL USA, Inc."— Presentation transcript:
Technology Transition Workshop DART and Trace Evidence (a bag of tricks for using DART) Robert B. Cody JEOL USA, Inc.
Technology Transition Workshop 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
Technology Transition Workshop Dopants, adducts Some compounds don’t form MH + or [M-H] - Ammonia, NH 4 OH useful for forming [M+NH 4 ] + 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
Technology Transition Workshop Dopant addition DART NH 4 OH, MeCl 2 on swab Sample or liquid in vial with capillary into gas stream…or…
Technology Transition Workshop 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+NH 4 ] + if ammonium is present
Technology Transition Workshop 1. Volatiles, headspace: direct 50100150200250300350400450 m/z 50100150200250300350400450 m/z 50100150200250300350400450 m/z Diesel fuel standard Carpet burned with diesel Burnt carpet (no accelerant) Scale x50
Technology Transition Workshop 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) Direct analysis of volatiles
Technology Transition Workshop 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 He Adsorbant in heatable trap to DART
Technology Transition Workshop 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) 2. Expose SPME fiber to headspace or liquid solution for several minutes 3. Hold fiber in DART gas stream (250 degrees C)
Technology Transition Workshop 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
Technology Transition Workshop Polyhydroxy compounds Derivatization with TMSI/Pyridine Commercially available –e.g. Pierce Tri-Sil-Z R 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.
Technology Transition Workshop -Cyclodextrin C 48 H 80 O 40 Underivatized MW 1296.4 8 amyloses 24 hydroxyls 24 TMS’s 100 % Rel. Abundance 2549261926892759282928992969303931093179 m/z -CD+TMS n +C 3 H 5 N 2 ] + n=19 n=20 n=21 n=22 n=23 n=24
Technology Transition Workshop Aminoglycoside antibiotics 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 950100010501100115012001250 m/z n = 7 n = 8 n = 6 n = 5 Neomycin sulfate C 23 H 46 N 6 O 13. 3H 2 SO 4 [M+TMS n +H] + See 1 extra (small) TMS for these compounds
Technology Transition Workshop Melamine C 3 H 6 N 6 MH + = 127.073 127.072 Melamine detected in pet food by Teresa Vail (University of the Pacific) 6 exchangeable H’s
Technology Transition Workshop Melamine H/D Exchange MH + 7: [D 6 -melamine+D] + Melamine: with D 2 O Melamine: No D 2 O C3H6N6C3H6N6 1 2 34 5 6
Technology Transition Workshop BT (Bacillus Thuringensis) Spores Garden Pest Control DART+ / He Heated with TMAH MH + Dipicolinic acid dimethyl ester Spore Biomarker
Technology Transition Workshop Counterfeit materials Presence or absence of critical ingredients (e.g. active pharmaceutical ingredients) Differences in the presence or absence of trace impurities
Technology Transition Workshop Genuine and Counterfeit CialisTablets Courtesy Tony Moffat (U. London Pharmacy) Sildenafil (Viagra) Tadalafil (Cialis) Genuine Counterfeit Other tablet components
Technology Transition Workshop Counterfeit Antimalarials “Yaa-chud” (Combination medicine) 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. Samples from Prof. Facundo Fernandez Georgia Tech
Technology Transition Workshop 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
Technology Transition Workshop Real (top) vs. Counterfeit Marlboro Brand Cigarette Volatile trace components are different Nicotine
Technology Transition Workshop 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
Technology Transition Workshop AutoDART: Promazine (Chlorpromazine I.S.) 5 replicates, 7 concentrations, 250 ppb to 250 ppm, CV = 4.5% Linear fit
Technology Transition Workshop Enhanced Ion Collection with Vacuum Pump IonSense GIST Implementation Reported BMSS 9/07 DART Tube Pump Orifice GIST on AccuTOF
Technology Transition Workshop IonSense Vapur TM 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.
Technology Transition Workshop 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.
Technology Transition Workshop Material ID: Latex from J&J Band-Aid 277.2906 C 20 H 37 + 345.3535 C 25 H 45 + 413.4145 C 30 H 53 + 481.4807 C 35 H 61 + 279.1612 C 16 H 23 O 4 + 551.5575 C 40 H 71 + 619.6162 C 45 H 79 + Searchable polymer library spectrum All compositions confirmed by exact masses C 5 H 8 (isoprene) units m/z 279=Dibutyl phthalate (plasticizer)
Technology Transition Workshop 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.
Technology Transition Workshop CS (Tear gas) Detected Directly on Cloth 100200300400500 m/z [M+H] + [M+H+H 2 O] + [2M+H] + 2-Chlorobenzalmalononitrile CAS # 2698-41-1 Formula: C 10 H 5 ClN 2 189.0209 207.0311 377.0348
Technology Transition Workshop Other DART CI Reagents ReagentIE (eV)P.A. (kJ/mol)Reagent Ion Water12.621691H3O+H3O+ Oxygen12.0697421O 2 +. Ammonia10.070853.6NH 4 + Nitric oxide9.2642531.8NO +. Fluorobenzene9.20755.9C 6 H 5 F +. Values from http://webbook.nist.gov
Technology Transition Workshop 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?
Technology Transition Workshop Charge-Exchange DART Oxygen He * + O 2 → O 2 +. + e - + He O 2 +. + S → S +. + O 2 O 2 +. + S → Fragment + + O 2 + R. (IE of sample S < 12.07 eV) Fluorobenzene He * + C 6 H 5 F → C 6 H 5 F +. + e - + He C 6 H 5 F +. + S → S +. + C 6 H 5 F C 6 H 5 F +. + S → [Fragment] + + C 6 H 5 F + R. (IE of sample S < 9.2 eV)
Technology Transition Workshop Normal DART Parameters DART O 2 +. Charge Exchange Electron ionization n-Hexadecane M+.M+. [M-H] + [M-H+O] + [M-3H+2O] +
Technology Transition Workshop Helium 200 degrees Helium 300 degrees Hexadecane : Fragmentation vs. temperature
Technology Transition Workshop Atmospheric Pressure Thermal Ionization for Inorganics & Metals Easy way to add some qualitative inorganic analysis capabilities to system configured for DART. Use hand-held butane torch to heat samples in DART gas stream. High orifice potential breaks up clusters & adducts to maximize atomic ions. Can also use the electrospray source