
Analysis of Gunshot Residue By XRay Fluorescence, Raman
Spectroscopy, and Inductively
Coupled Plasma
Delaney Caudill
Courtney Belanger
Background
 Gunshot Residue (GSR) is a type of physical trace
evidence that is released when a gun is fired
 Analysis of GSR is an important technique in
forensic science
 It may place an individual at the scene of the
crime
 GSR is composed of inorganic and organic
components
Significance and Purpose
 To allow for nondestructive forensic analysis and
detection
 To detect GSR components using XRF and
Raman
 To quantify concentrations of GSR analytes using
the ICP
Samples and Analytes
Samples
Caliber
Distance
.22
< 3 feet
.38
< 3 feet
.45
< 3 feet
Shotgun: 12 gauge
4-5 feet
Inorganic
Organic
Iron
Ethyl Centralite
Copper
2-Nitrodiphenylamine
Lead
Barium
Zinc
Method: XRF
 Spiked sample was created
 Solid reference and unknown samples were
directly placed on XRF
Method: XRF
 Soaked reference and unknown sample in 10
mL of 0.1 M nitric acid
 Soaked for 48 hr
 Pipetted 1 mL of solution into liquid sample
holder for XRF
Method: Raman
• Soaked four unknown samples for 1.5 weeks in 10 mL of MEK
Samples
Methyl ethyl Ketone (MEK solvent)
Solid Ethyl Centralite Standard
Solid 2-Nitrodiphenylamine Standard
100 mg of ethyl centralite in 0.5 mL of MEK
100 mg of 2-Nitrodiphenylamine in 0.5 mL of MEK
.22 Caliber
.38 Caliber
.45 Caliber
Shotgun: 12 gauge
Method: ICP
 Standards were created: 5, 10, 20, 30, 40 ppm
 Unknown samples soaked for 2 weeks before
analysis by ICP
 Standards and unknown samples were run on
ICP
Results: Raman
Raman
Compound
Relative Shifts (1/cm)
Methyl Ethyl Ketone
2976.000, 2920.743, 1710.000, 1084.000,
759.000
Ethyl Centralite
2971.981, 3063.748, 2933.020,
705.528,428.901, 1455.783
2-Nitrodiphenylamine
1144.701, 1255.381, 204.184
.22 Caliber
2978.795, 2920.972, 2735.317, 1712.384,
1084.200, 759.522
.38 Caliber
2976.523, 2920.897, 2735.063, 1709.513,
1085.329, 759.961
.45 Caliber
2978.502, 2920.782, 2737.978, 1711.065,
1083.950, 760.048, 585.511, 408.906
Shotgun (12 Gauge)
2977.995, 2920.835, 2733.644, 1709.547,
1084.542, 759.548, 405. 193
Results: XRF
Solid Cloth Sample (% Composition)
Analyte
Barium
Copper
Iron
Lead
Zinc
.22 caliber
9.830
1.621
1.356
64.044
0.496
.38 caliber
N/A
1.836
1.739
3.269
N/A
.45 Caliber
12.990
11.337
0.553
17.053
1.644
Shotgun
N/A
1.876
2.317
10.201
N/A
Liquid Sample (% Composition)
Analyte
Barium
Copper
Iron
Lead
Zinc
.22 caliber
N/A
18.201
N/A
N/A
N/A
.38 caliber
N/A
13.936
N/A
N/A
N/A
.45 Caliber
N/A
15.754
N/A
N/A
N/A
Shotgun
N/A
7.724
N/A
N/A
N/A
Results: ICP
Concentration [ppm]
Analyte
Barium
Copper
Iron
Lead
Zinc
.22 caliber
19.6
13.6
20.1
20.8
15.6
.38 caliber
1346.6
70.3
640.0
958.7
48.5
.45 caliber
856.7
59.2
516.9
654.2
28.8
Shotgun
1153.0
63.9
1023.9
1740.4
44.9
Sample Calculation:
Ex. .22 Caliber/ Barium
8688.5=556.28x-220.9
x=19.58 ppm
ICP Calibration Curves
ICP Calibration Curves
Discussion
 Raman did not conclusively identify analytes
•
•
May have needed more time to soak
Could have been overwhelmed by solvent
 XRF was able to detect each analyte of interest within
solid method.
• At relatively similar distances, there seems to be no
correlation between caliber size and percent
composition
Discussion
 XRF was only able to detect a percent composition of
copper within liquid method
• May need to be soaked for longer to detect other
analytes
 ICP successfully quantified analytes of interest
•
Generally, the .38 caliber had the highest
concentration for each analyte when compared to
the 3 calibers but had no correlation with the shotgun
References
 Bueno, J; Sikirzhytski, V; Lednev, I. Raman Spectroscopic
Analysis of Gunshot Residue Offering Great Potential for
Caliber Differentiation. Analytical Chem. [Online] 2011, 1021,
A-F
 Lopez-Lopez, M; Delgado, J. J; Garcia-Ruiz, C. Ammunition
Identification by Means of the Organic Analysis of Gunshot
Residues Using Raman Spectroscopy. Analytical Chem.
[Online] 2012, 1021, A-D
Special Thanks
 Matt Cunningham for providing GSR samples
 Dr. Foy for letting us play with really expensive instruments
 Our lab assistants: Kiersten and Pat L.
 Professor Mowery for ordering our chemicals
Look at that
center burst!