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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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outline
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
dopants adducts
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

dopant addition
Dopant addition

NH4OH, MeCl2

on swab

Sample

DART

or liquid in vial with capillary into gas stream…or…

example organic acids e g aspirin
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

explosives detected on wipe
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

nitroglycerin on an employee s tie 8 hours after walking through plume from construction blasting
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

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

1. Direct analysis

2. Adsorbant (e.g. Tenax), thermal desorption

3. Solid-phase microextraction

1 volatiles headspace direct

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

direct analysis of volatiles
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)
2 volatiles headspace trap
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

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

prep spme dart irish whiskey
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

derivatization and reactions
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
polyhydroxy compounds derivatization with tmsi pyridine
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.

g cyclodextrin
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

aminoglycoside antibiotics
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

melamine detected in pet food by teresa vail university of the pacific
Melamine detected in pet food by Teresa Vail (University of the Pacific)

127.072

Melamine

C3H6N6

MH+ = 127.073

6 exchangeable H’s

melamine h d exchange
Melamine H/D Exchange

7: [D6-melamine+D]+

Melamine: with D2O

6

5

3

4

1

2

Melamine: No D2O

MH+

C3H6N6

bt bacillus thuringensis spores garden pest control
BT (Bacillus Thuringensis) SporesGarden Pest Control

Spore Biomarker

MH+

Dipicolinic acid dimethyl ester

DART+ / He

Heated with TMAH

counterfeit materials
Counterfeit materials
  • Presence or absence of critical ingredients (e.g. active pharmaceutical ingredients)
  • Differences in the presence or absence of trace impurities
genuine and counterfeit cialistablets courtesy tony moffat u london pharmacy
Genuine and Counterfeit CialisTabletsCourtesy Tony Moffat (U. London Pharmacy)

Tadalafil (Cialis)

Genuine

Other tablet components

Sildenafil (Viagra)

Counterfeit

counterfeit antimalarials yaa chud combination medicine
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.

counterfeit antimalarials were found to contain
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

real top vs counterfeit marlboro brand cigarette
Real (top) vs. Counterfeit Marlboro Brand Cigarette

Volatiletrace components

are different

Nicotine

dart quantitation
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

autodart promazine chlorpromazine i s
AutoDART: Promazine (Chlorpromazine I.S.)

5 replicates, 7 concentrations, 250 ppb to 250 ppm, CV = 4.5%

Linear fit

enhanced ion collection with vacuum pump
Enhanced Ion Collection with Vacuum Pump

Orifice

DART

Tube

Pump

IonSense GIST ImplementationReported BMSS 9/07

GIST on AccuTOF

autodart gist lower detection limits chlorpromazine promazine i s
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

ionsense vapur tm pro s and con s
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.
another kind of information
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.

polymers
Polymers

Nylon 6

poly(caprolactam)

Polyethylene terephthalate

material id latex from j j band aid
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)
3 beige paint chips
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.
condom lubricants
Condom lubricants

Condom swab

Post-coital

vaginal swab

slide42

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

other dart ci reagents
Other DART CI Reagents

Values from http://webbook.nist.gov

proton transfer is very useful but it is not universal
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?

different dart chemistries
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

slide46

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)

n hexadecane
n-Hexadecane

Normal DART Parameters

[M-H+O]+

[M-H]+

[M-3H+2O]+

DART O2+. Charge Exchange

M+.

Electron ionization

hexadecane fragmentation vs temperature
Hexadecane : Fragmentation vs. temperature

Helium 200 degrees

Helium 300 degrees

slide49

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

slide50

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
slide51

GC-DART: Grob Mix TICs

  • 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

13

6

8

Standard DART

parameters

CI spectra

10,11,12

9

5

3

1

atmospheric pressure thermal ionization for inorganics metals54
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

lead in paint chip
Lead in paint chip

PbOH+

224.9787

100

207.9744

PbO2H3+

100

80

264.9724

Pb+

50

60

Rel. Abund.

Pb2(OH)3+

Rel. Abund.

40

20

224.9764

0

114.9051

84.9135

80

140

200

260

320

380

440

500

560

620

680

0

100

150

200

250

Pb+

PbOH+

In+

Rb+

m/z

Orifice1=20V

Orifice 1=90V

stainless steel wire
Stainless Steel Wire

55.9349

Fe+

100

80

60

Rel. Abundance

40

Cu+

FeOH+

Mn+

Ni+

62.9294

20

Ga+

72.9400

Cr+

0

50

60

70

80

m/z

Plunger wire from

PCR Pipette