OSAC 2022-S-0002 Standard Practice for the Analysis of Identification

Of Compounds Related to Organic Gunshot Residue (OGSR)

by Gas Chromatography-Mass Spectrometry (GC-MS)

1

OSAC 2022-S-0002 Standard 

Practice for the Identification of 

Compounds Related to Organic 

Gunshot Residue (OGSR) by Gas 

Chromatography-Mass 

Spectrometry (GC-MS)

Ignitable Liquids, Explosive, and Gunshot Residue Subcommittee

Chemistry: Trace Evidence Scientific Area Committee (SAC)

Organization of Scientific Area Committees (OSAC) for Forensic Science
OSAC 2022-S-0002 Standard Practice for the Analysis of Identification

Of Compounds Related to Organic Gunshot Residue (OGSR)

by Gas Chromatography-Mass Spectrometry (GC-MS)

2

OSAC Proposed Standard

OSAC 2022-S-0002

Standard Practice for the 

Identification of Compounds Related 

to Organic Gunshot Residue (OGSR) 

by Gas Chromatography-Mass 

Spectrometry (GC-MS)

Prepared by 

Ignitable Liquids, Explosive, and Gunshot Residue Subcommittee

Version: 2.0

November 2022

Disclaimer:

This OSAC Proposed Standard was written by the Organization of Scientific Area Committees 

(OSAC) for Forensic Science following a process that includes an open comment period. This 

Proposed Standard will be submitted to a standards developing organization and is subject to 

change. 

There may be references in an OSAC Proposed Standard to other publications under 

development by OSAC. The information in the Proposed Standard, and underlying concepts and 

methodologies, may be used by the forensic-science community before the completion of such 

companion publications.

Any identification of commercial equipment, instruments, or materials in the Proposed Standard 

is not a recommendation or endorsement by the U.S. Government and does not imply that the 

equipment, instruments, or materials are necessarily the best available for the purpose.

To be placed on the OSAC Registry, certain types of standards first must be reviewed by a 

Scientific and Technical Review Panel (STRP). The STRP process is vital to OSAC’s mission of 

generating and recognizing scientifically sound standards for producing and interpreting forensic 

science results. The STRP shall provide critical and knowledgeable reviews of draft standards or 
OSAC 2022-S-0002 Standard Practice for the Analysis of Identification

Of Compounds Related to Organic Gunshot Residue (OGSR)

by Gas Chromatography-Mass Spectrometry (GC-MS)

3

of proposed revisions of standards previously published by standards developing organizations 

(SDOs) to ensure that the published methods that practitioners employ are scientifically valid, 

and the resulting claims are trustworthy.

The STRP panel will consist of an independent and diverse panel, including subject matter 

experts, human factors scientists, quality assurance personnel, and legal experts, which will be 

tasked with evaluating the proposed standard based on a comprehensive list of science-based 

criteria. 

For more information about this important process, please visit our website 

at: https://www.nist.gov/topics/organization-scientific-area-committees-forensicscience/scientific-technical-review-panels. 
OSAC 2022-S-0002 Standard Practice for the Analysis of Identification

Of Compounds Related to Organic Gunshot Residue (OGSR)

by Gas Chromatography-Mass Spectrometry (GC-MS)

4

Standard Practice for the Identification of Compounds related to Organic Gunshot 

Residue (OGSR) by Gas Chromatography– Mass Spectrometry (GC-MS)

1. Scope

1.1. This practice covers the qualitative analysis of extracts using electron impact ionizationgas chromatography-mass spectrometry (GC-(EI)MS) to identify compounds related to 

organic gunshot residue (OGSR). 

1.2. This practice is intended for use by forensic science practitioners with the requisite 

formal education, discipline-specific training (see Practice E2917), and demonstrated 

competency to perform forensic casework. 

1.1. This practice does not purport to address all of the safety concerns, if any, associated 

with its use. It is the responsibility of the user of this practice to establish appropriate 

safety and health practices and determine the applicability of regulatory limitations prior 

to use.

2. Referenced Documents

2.1. ASTM Standards:

E1588 Practice for Gunshot Residue analysis by Scanning Electron Microscopy/Energy 

Dispersive X-ray Spectrometry.

E1732 Terminology Relating to Forensic Science.

E2917 Practice for Forensic Science Practitioner Training, Continuing Education, and 

Professional Development Programs.

E2998 Practice for Characterization and Classification of Smokeless Powders.

E2999 Test Method for Analysis of Organic Compounds in Smokeless Powder by Gas 

Chromatography-Mass Spectrometry and Fourier Transform Infrared 

Spectroscopy.

E3255 Practice for Quality Assurance of Forensic Science Service Providers Performing 

Forensic Chemistry Analyses.

WK56998 Terminology Relating to the Examination of Explosives.

OSAC 2021-N-0009 Standard Practice for the Collection and Preservation of Organic 

Gunshot Residue

OSAC 2022-S-0003 Standard Practice for the Identification of Compounds related to 

Organic Gunshot Residue (OGSR) by Liquid Chromatography-Mass Spectrometry 

(LC-MS).

3. Terminology

3.1. For definitions of terms that can assist in interpreting this standard, refer to Terminology 

E1732 and WK 56998. 

3.2. Definitions of terms specific to this standard:
OSAC 2022-S-0002 Standard Practice for the Analysis of Identification

Of Compounds Related to Organic Gunshot Residue (OGSR)

by Gas Chromatography-Mass Spectrometry (GC-MS)

5

3.2.1. Inorganic GSR (IGSR), n – Gunshot residues from the primer, cartridge case, 

projectile (e.g., bullet or shot pellets), or the firearm which are typically identified 

using scanning electron microscope (E1588).

3.2.2. Organic GSR (OGSR), n – Gunshot residues from the propellant and the priming 

mixture that are organic (carbon-based).

3.2.3. Primer GSR (pGSR), n – Gunshot residues generating from the priming mixture 

that could be inorganic or organic.

3.2.4. Reference Sample, n – A solution containing known target OGSR compounds.

4. Significance and Use

4.1. Gunshot residue (GSR) examination is typically performed to determine if an individual 

or object was exposed to firearm discharge. GSR analysis has historically relied upon the 

detection of IGSR, as described in Practice E1588, which originates primarily from the 

ammunition primer (pGSR). OGSR analysis provides information which complements 

pGSR analysis [1].

4.2. OGSR originates from the combustion of the priming mixture and the smokeless powder 

following their ignition during the firearm discharge process. After a firearm has been 

discharged, the combined residue can be found on exposed surfaces in the vicinity of the 

fired weapon (e.g., hands, other skin surfaces, hair, clothing, and other surfaces). OGSR 

can also be found in the cartridge case after firing and can be recovered to provide 

information about the constituents of the propellant or the priming mixture, or both.

4.3. This practice is intended to be used in conjunction with a laboratory’s validated standard 

operating procedures. Laboratory specific criteria should be established and supported by 

data obtained during method development and validation (E3255).

4.4. This practice does not cover how to interpret analytical data for reporting the absence or 

presence of OGSR. 

4.4.1. This practice can be used in tandem with other practices (E1588) or approaches to 

simultaneously or independently identify components related to OGSR or 

IGSR/pGSR.

4.5. The analysis of smokeless powder grains is beyond the scope of this practice (refer to 

Practice E2998 and Test Method E2999).

4.6. This practice does not address the analysis of inorganic gunshot residue (IGSR) or 

primer gunshot residue (pGSR).

5. Apparatus

5.1. Gas chromatograph (GC) – A gas chromatograph (GC) capable of using capillary columns 

and being interfaced to a mass spectrometer (MS) (refer to Table X1).

5.2. Mass Spectrometer (MS) – A mass selective detector operating in electron ionization (EI) 

mode and capable of acquiring mass spectra from mass-to-charge (m/z) 10 - m/z 400 with 

unit resolution or better.

5.3. Sonicator – For use when extracting OGSR components from sample items collected. 
OSAC 2022-S-0002 Standard Practice for the Analysis of Identification

Of Compounds Related to Organic Gunshot Residue (OGSR)

by Gas Chromatography-Mass Spectrometry (GC-MS)

6

5.4. Centrifuge – Recommended for use after sonication of extract and capable of achieving a 

minimum of 4000 RPM. Disposable centrifuge tubes that safely fit the centrifuge device 

are required.

6. Materials 

6.1. Analytical Solvents – Acetone, acetonitrile, ethanol, isopropanol, methanol, methylene 

chloride, or other solvents compatible with GC-MS.

6.1.1. Purity of Solvents – GC-MS grade or higher.

6.2. OGSR Standard(s) or Reference Materials – Certified reference materials are to be used. 

Individual reference materials or standards, or mixture thereof, may be used in place of a 

certified reference standard provided that they are verified according to laboratory 

protocol before use.

6.3. Internal Standard – Use of an internal standard is not required for qualitative identification 

of OGSR but can be used to evaluate system sensitivity and reproducibility.

6.4. GC Carrier Gas – Helium or hydrogen of purity 99.995% or higher.

6.5. Drying Gas – Nitrogen, air, or other inert gas of purity 99.95% or higher.

6.6. Filters – Single use disposable filters of a hydrophobic membrane construction are 

recommended for use to filter the extract prior to analysis. A filter membrane porosity of 

0.4 μm or smaller is required. 

7. Procedure

7.1. Samples are submitted for OGSR analysis in one or more of the following forms: 

adhesive tape lifts, swabs, or vacuum filters; refer to OSAC 2021-N-0009.

7.1.1. Alternative analysis of OGSR components by LC-MS has been described 

elsewhere [OSAC 2021-S-0003] [2, 3].

7.2. Preparation of OGSR samples:

7.2.1. Extract collection items such as swabs, vacuum filters, or adhesive lifts using a 

suitable organic solvent, such as methanol, methylene chloride, or acetonitrile 

[4].

7.2.2. Place the entire collection item inside a new disposable vial suitable for the size 

of the collection item. Swabs can be folded to fit into the vial. Add a minimum 

volume of solvent required to submerge the item. 

7.2.2.1. If an aluminum stub with an adhesive carbon tab was used to collect the 

sample, place the entire stub into a new disposable vial for subsequent 

extraction (using the process in Section 7.2.2.)

7.2.2.2. Alternatively, wash the surface of the stub with multiple aliquots of the 

solvent using repeated cycles of suction and addition [5].

7.2.3. Sonicate the vial with the item submerged in the solvent for a minimum of 5 

minutes [6]. Remove the extract and either filter or centrifuge the item to remove 

any solid particulates from the solution.

7.2.4. The extract can be analyzed directly but concentration is often required for GCMS analysis of OGSR components. 
OSAC 2022-S-0002 Standard Practice for the Analysis of Identification

Of Compounds Related to Organic Gunshot Residue (OGSR)

by Gas Chromatography-Mass Spectrometry (GC-MS)

7

7.2.5. Carefully dry the extract down to an appropriate volume required for injection

using a gentle stream of drying gas. If the extract is taken to complete dryness, 

some of the OGSR components may be lost.

7.2.6. Store extracts at 0°C or colder to maximize preservation when the sample is not 

being analyzed.

7.3. GC-MS analysis of OGSR extracts:

7.3.1. Common organic components of OGSR can be identified by GC-MS analysis. 

7.3.2. Suggested GC-MS parameters are listed in Appendix Table X1.

7.3.2.1. Verify that these parameters are optimized to ensure that each peak in the 

reference test mixture has baseline resolution (less than 1% overlap between 

two peaks) on the laboratory’s instrument before using the method in 

casework.

7.3.3. Prior to analyzing samples, the GC-MS should be tuned and calibrated per 

validation protocols or the manufacturer recommendations.

7.3.4. Table 1 lists the common compounds related to OGSR and their target ions .

7.3.4.1. Data analysis is limited to the identification of the target compounds listed in 

Table 1.

7.3.4.2. Each specific retention time is measured by analyzing a reference material (see 

Sec. 6.3), using the GC-MS system and method under the same instrumental 

conditions [7,8]. 

7.3.4.3. Nitroglycerin and trinitrotoluene are subject to thermal degradation in the 

injection port of the GC which may make them difficult to detect at trace 

levels. 

TABLE 1: Typical OGSR related compounds and m/z of target ions in EI MS found by GCMS analysis. Refer to the citations for further details on identification. 

Target Compound Significance/ Application Target Ions (m/z)* Ref.

Akardite II (AK II) Stabilizer 169, 226 [9, 10 E2999]

2-amine-4,6-dinitrotoluene (2-ADNT) Degradation products 197, 180 [9]

Dibutyl phthalate (DBP) Plasticizer 149, 223 [9, 10 E2999]

Diisoamyl phthalate (DIP) Plasticizer 149 [E2999]

2,4- and 2,6-dinitrotoluene (2,4-DNT and 2,6-

DNT)

Flash suppressor 165, 182 [9, 10 E2999]

Dioctyl phthalate (DOP) Plasticizer 149, 279 [9, 10 E2999]

Diphenylamine (DPA) Stabilizer 169 [9, 10 E2999]

Ethyl centralite (EC) Stabilizer 120, 268 [9, 10 E2999]

Ethyleneglycol dinitrate (EGDN) Explosive 46, 76 [9, 10 E2999]

Methyl centralite (MC) Stabilizer 134, 240 [9, 10 E2999]

2 and 4-nitrodiphenylamine (2-NDPA, 4-

NDPA)

Degradation products; 

stabilizer

167, 214 [9, 10 E2999]

Nitroglycerin (NG) Explosive 46, 76 [9, 10 E2999]

4-nitrosodiphenylamine (4-NODPA) Degradation products 167, 198 [9, 10 E2999]
OSAC 2022-S-0002 Standard Practice for the Analysis of Identification

Of Compounds Related to Organic Gunshot Residue (OGSR)

by Gas Chromatography-Mass Spectrometry (GC-MS)

8

N-nitrosodiphenlyamine (N-NODPA) Degradation product 168, Detected as 

DPA

[9, 10]

Nitrotoluenes (NTs) Sensitizer 65, 91, 120 or 137 [9, 10 E2999]

2,4,6-trinitrotoluene (TNT) Flash suppressor/sensitizer 89, 210 [10]

* NOTE: Full scan or selected ion monitoring (SIM) analysis using all target ions

8. Identification of Compounds related to OGSR 

8.1. The identification of a compound in an unknown sample shall be based upon direct 

comparison with a known reference standard of the compound.

8.1.1. The retention time or retention index and the mass spectral pattern (ions detected 

and their m/z values), and the mass spectral pattern as compared to the certified 

reference standard must be used for compound identification.

8.2. The unknown sample shall be run on the same instrument using the same instrument 

parameters and the same method as the known reference standard.

8.3. In order to identify any compound in an unknown sample, the compound should meet 

identification criteria for gas chromatography retention time and mass spectrometry.

8.3.1. Gas Chromatography

8.3.1.1. The retention time of the compound in the unknown sample shall be within 

± 0.1 minute of the reference compound.

8.3.2. Mass Spectrometry

8.3.2.1. The unknown and reference samples shall have the same base peak and the 

same molecular ion, if present. 

8.3.2.2. The measured m/z value of the molecular ion shall be within the instrument 

manufacturer’s tolerance (mass accuracy) of the molecular ion peak 

observed in the corresponding mass spectrum of the certified reference 

standard. 

8.3.2.3. The fragmentation patterns and relative abundances of target ions in the 

mass spectra of the unknown sample and the reference OGSR sample must 

not have unexplainable differences across the majority of the ions.

8.3.2.3.1. Analysts must document reasons for considering or not considering 

differences between the spectra.

8.3.2.4. When blank subtraction is performed, use the blanks described in 9.2.2.

8.3.2.5. There shall be no ions (above 5% of total spectral abundance) that cannot be 

attributed to the instrument’s background. 

9. Quality Control

9.1. For minimum quality assurance protocols refer to Practice E3255.

9.2. Quality assurance protocols specific to this standard practice:

9.2.1. Analyze a quality control sample with questioned extracts.

9.2.1.1. The quality control sample shall be analyzed, at minimum, at the beginning 

and the end of the analytical sequence on the instrument.
OSAC 2022-S-0002 Standard Practice for the Analysis of Identification

Of Compounds Related to Organic Gunshot Residue (OGSR)

by Gas Chromatography-Mass Spectrometry (GC-MS)

9

9.2.1.2. Quality control sample shall contain at least five compounds, as chosen by 

the individual laboratory, from the compounds s listed in Table 1.

NOTE: An example of a quality control sample is as follows: NG, EC, 2-

NDPA, DPA, and 2,4-DNT prepared at a concentration within the method's 

linear dynamic range.

9.2.1.3. Establish protocols to ensure stability of the quality control sample.

9.2.1.4. Store quality control sample under appropriate conditions (see 7.2.5).

9.2.1.5. Replace the quality control sample when degradation is observed from the 

previous analysis of the sample. Examples of degradation include: the 

absence of peaks, the presence of new peaks. The laboratory can also 

determine an expiration date for the quality control sample in accordance with 

laboratory policy.

9.2.1.5.1. If degradation of the quality control was observed during analysis, any 

affected questioned samples must be reanalyzed with a new quality 

control.

9.2.2. Analyze the following blank samples with each batch of questioned extracts.

9.2.2.1. Prepare a method blank by extracting a clean swab or filter using the same 

procedure(s), reagents, and conditions used to extract the unknown sample(s).

9.2.2.2. A solvent blank, consisting of solvent alone, shall be analyzed between each 

sample to ensure no carryover occurs.

10. Records

10.1. Document the following, electronically or hard-copied, refer to Practice E3255:

10.1.1. GC-MS instrument settings and method parameters used for analysis.

10.1.2. Calibration and tuning of the instrument used for analysis.

10.1.3. Chromatograms of method blank(s), reference material(s), and questioned 

samples. Annotate all peaks relevant to the analysis with retention times.

10.1.4. Mass spectra of OGSR compounds identified and the associated material(s) used 

for comparison. 

10.1.5. All analytical notes from the analysis including the details of sample preparation 

and instrument performance checks. 

10.1.6. Maintain reports in accordance with laboratory policy and Practice E3255.

11. Keywords

11.1. OGSR; GC-MS

12. References

[1] W. Feeney, C. Vander Pyl, S. Bell, T. Trejos. Trends in composition, collection, persistence, 

and analysis of IGSR and OGSR: A review. For Chem 19 (2020), 100250. 
OSAC 2022-S-0002 Standard Practice for the Analysis of Identification

Of Compounds Related to Organic Gunshot Residue (OGSR)

by Gas Chromatography-Mass Spectrometry (GC-MS)

10

[2] E. Bernal Morales, A.L. Revilla Vázquez, Simultaneous determination of inorganic and 

organic gunshot residues by capillary electrophoresis, J Chromatogr A 1061 (2004), 225-

233. 10.1016/j.chroma.2004.10.083.

[3] M. Morelato, A. Beavis, A. Ogle, P. Doble, P. Kirkbride, C. Roux, Screening of gunshot 

residues using desorption electrospray ionisation–mass spectrometry (DESI–MS), Forensic 

Sci Int 217 (2012), 101-106. https://doi.org/10.1016/j.forsciint.2011.10.030.

[4] E. Goudsmits, G.P. Sharples, J.W. Birkett, Recent trends in organic gunshot residue 

analysis, TrAC Trends in Anal Chem 74 (2015), 46-57. 10.1016/j.trac.2015.05.010.

[5] C. Bonnar, E.C. Moule, N. Lucas, K.E. Seyfang, R.P. Dunsmore, R.S. Popelka-Filcoff, K. 

Redman, P. Kirkbride, Tandem detection of organic and inorganic gunshot residues using 

LC-MS and SEM-EDS, For Sci Intl 314 (2020), 110389. 10.1016/j.forsciint.2020.110389.

[6] S. Benito, Z. Abrego, A. Sanchez, N. Unceta, M.A. Goicolea, R.J. Barrio, Characterization 

of organic gunshot residues in lead-free ammunition using a new sample collection device 

for liquid chromatography-quadrupole time-of-flight mass spectrometry. Forensic Sci Int 

246 (2015) 79-85.

[7] A.S. Chajistamatiou, E.B. Bakeas, A rapid method for the identification of nitrocellulose in 

high explosives and smokeless powders using GC-EI-MS, Talanta 151 (2016), 192-201. 

10.1016/j.talanta.2016.01.038.

[8] E. Goudsmits, G.P. Sharples, J.W. Birkett, Preliminary classification of characteristic 

organic gunshot residue compounds, Sci Justice 56 (2016), 421-425. 

10.1016/j.scijus.2016.06.007.

[9] Wallace, M. W., "Mass Spectra" in NIST Chemistry WebBook, NIST Standard Reference 

Database Number 69, Eds. P.J. Linstrom and W.G. Mallard, National Institute of Standards 

and Technology, Gaithersburg MD, 20899, https://doi.org/10.18434/T4D303, (retrieved 

February 9, 2022).

[10] R.V. Taudte, A. Beavis, L. Blanes, N. Cole, P. Doble, C. Roux, Detection of gunshot 

residues using mass spectrometry, Biomed Res Int 2014 (2014) 965403.
OSAC 2022-S-0002 Standard Practice for the Analysis of Identification

Of Compounds Related to Organic Gunshot Residue (OGSR)

by Gas Chromatography-Mass Spectrometry (GC-MS)

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APPENDIX

(Non-Mandatory Information)

X1. Instrumental Operation Parameters

X1.1 Suggested GC-MS parameters 

X1.1.1 An example GC-MS instrumental method, from literature, to analyze OGSR 

compounds is provided below as a starting point for the method validation by the laboratory.

 TABLE X1: Suggested GC-MS conditions derived from ASTM E2999.

Parameter Condition

GC column: 30 meters, DB-5, 

Injector Temp: 180° C

Initial Temp (T0): 40-50° C

Hold time (T0): 3 minutes

Ramp 1: 15° C/minute to 150° C (T1)

Hold time (T1): 2 minutes

Ramp 2: 20-40° C/minute to 265° C (T2)

Hold time (T2): 8 minutes

Mode: EI

Scan Mode Full Scan or Selected Ion Monitoring

Split Ratio: Splitless (n/a)

MS range: 40 to 400 m/z

Source Temp: 230° C

Solvent delay: 1-2 minutes