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Detection of Organic Gunshot Residue Using Capillary Microextraction of Volatiles With Cryofocusing

NCJ Number
Date Published
July 2017
8 pages
This is the executive summary of the report on an evaluation of the capability of capillary microextraction of volatiles (CMV) to extract the volatile organic compounds (VOCs) that constitute organic gunshot residue (OGSR), which was conducted by researchers at Florida International University's International Forensic Research Institute with funding by the National Institute of Justice (NIJ).
The overall purpose of the project was to optimize a field sampling method for the detection of OGSR. This effort included designing a custom-built Peltier cooling device for CMV in order to assess whether cryofocusing during the extraction process could improve the detection of OGSR in real-world samples. The project found that cryofocusing of the CMV device with a thermoelectric cooler achieved improved recoveries of nitroglycerin (NG) extracted from the headspace of double-base smokeless powder samples. Improving the extraction method resulted in greater recoveries from mock swab samples spiked with VOCs typically present in OGSR. The equilibrium time, sample temperature, pump flow rate, extraction time, and sampling volume were all key factors requiring optimization. The volume of the container (15-mL vial vs. 1-L can) in which a sample is stored and from which extraction is done significantly affects the amount recovered from the headspace. Vials provide better recoveries and may be more suitable for the storage of field samples. The CMV desorption temperature in the inlet of the gas chromatograph (GC) is important for the sensitive detection of NG. Also, hand blank samples collected in a similar fashion to the actual shooter's swabs did not show chromatographic interference. Sample extraction and analysis with GC-mass spectrometry can be completed in approximately 30 min. 5 figures, 1 table, and 6 references

Date Published: July 1, 2017