gc-ms & smokeless powders --- summer internship me's office 2016
TRANSCRIPT
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SMOKELESS POWDERS LIBRARY
Jess Seng
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What is a GC-MS instrument?
Gas Chromatography• Column separates injected sample mixture • Mass of chemicals determines travel time
through column
Mass Spectroscopy • Molecules are charged & put through
magnetic field; become fragmented• Fragment mass & molecular mass used to
name sample
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GC-MS
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He
HeHe
He
He
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& accelerator
Quadrupole
Vacuum Chamber
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QUADRUPOLE: ELECTRIC FIELDS
Small ion
Large ion
Just right sized ion
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camph
or
nitrog
lyceri
n 2,4-
Di
nitro
toul
ene
Diet
hyl p
htha
late
Diph
enyl
amin
e
Ethy
l Cen
tralit
e2-
Nitro
diph
enyl
amin
eDi
buty
l ph
thal
ate
Diam
yl p
htha
late
4-Ni
troso
diph
enyl
amin
e
Ethylh
exyl
phtha
late
From solvent
9.2 11 1
2
12.3
12.4
13.4
13.5
14 14.2 16.4
13.7
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Methyl Centralite
Ethyl Centralite
Accurate-2495
13.2
13.4
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Nitroglycerin
Diphenylamin
e
Ethyl Centralite
Hodgdon-LEVERevolution
11 12.4
13.4
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What are smokeless powders?
• Smokeless powders are a form of propellant that replaced the use of black powder.• They leave little
residue; found as gun powder residue in guns or as explosive charge in IEDs.
D:
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Classes of powders Single-base: nitrocellulose
Double-base: nitrocellulose + nitroglycerine
Triple-base:nitrocellulose + nitroglycerine + nitroguanidine
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PROPELLANT AUTO IGNITION
Nitrocellulose slowly breaks down over time
In bulk, released heat could have negative effects
To stop, calcium carbonate may be added
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STABILIZER • In order to prevent decomposition products, stablizers
added. • Inserted in low quantities [0.5 – 2.0%]• Over time, stabilizer will degrade, so frequently tested
Common stabilizer? Diphenylamine
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Further forms of classification are morphology and color. . .
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BURN RATE & SURFACE AREA• Black powders never had distinguishing shapes.• Smokeless powders DO.
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NCFS EXPERIMENT PROTOCOL• Weighed out then cut in half 0.010 g of each sample of smokeless powder.
300ųl methylene chloride + smokeless powder [sat for 3 hours]
Extraction: Insert contains 100ųl of previous vial
Dilution: 10ųL of 1st vial placed in insert & 100ųL methylene chloride
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PROTOCOL CONTD. . .
• 2 microliter injections of sample analyzed with Agilent ALS autosampler G2614A splitless injector.
• Via transfer line, moves temp changes
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PROTOCOL CONTD. . .• Agilent 7890A GC/5975c EI MSD GC-MS used for analysis
• Restek Rtx-5ms crossbond 5% diphenyl/ 95% dimethyl polysiloxane • Helium carrier gas w/ flow rate of 1.2 mL/min on column & 40 cm/sec velocity
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ATR FT-IR
Sample platform
Pressure tower/compression tip
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ATR FT-IR PROTOCOL
• 2.5 mg uncut powder kernels placed in 100ųL of acetone; sat for 30 minutes
• Supernatant spotted onto microscope slide and allowed to evaporate, topped with another drop of supernatant and film placed on ATR-FTIR
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SABRE 5000
• Handheld trace detector for• Explosives• Chemical agents• Toxic industrial
chemicals• Narcotics
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Item loaded: Swab
Swab dabbed with sample
Blank swab loaded?
No alert! Keep searching!
Control with drug/bomb sample loaded?
ALERT! STOP! Positive sample acquired!
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Future applications of acquired results.• Better compare smokeless powders and look at stabilizers present in the
sample.
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Resources
• A Forensic Application of Mass Spectroscopy, Jehuda Yenon
• Practical Bomb Scene Investigation, James T. Thurman• Forensic Analysis on the Cutting Edge, Robert D. Blackledge• A Qualitative Comparison of Smokeless Powder Measurements, William A.
Mac Creham & Michelle R. Reardon• The Manufacture of Smokeless Powders & their Forensic Analysis: A Brief
Preview, Probert M. Heramb• National Center for Forensic Science Smokeless Powder Database
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QUESTIONS?
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THANK YOU VERY MUCH!