Analysis of Gunshot Residue By X-Ray 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

Inorganic Organic

Iron Ethyl Centralite

Copper 2-Nitrodiphenylamine

Lead

Barium

Zinc

Samples

Caliber Distance

.22 < 3 feet

.38 < 3 feet

.45 < 3 feet

Shotgun: 12 gauge 4-5 feet

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

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

• Soaked four unknown samples for 1.5 weeks in 10 mL of MEK

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: RamanRaman

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 Caliber2978.502, 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: XRFSolid 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/ALiquid 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 44.9Sample Calculation: Ex. .22 Caliber/ Barium8688.5=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!