Efficiency Comparison of Collection Methods for Organic and Inorganic Analytes in Gunshot Residue

Emily Halpern,* William Feeney and Tatiana Trejos, Department of Forensic and Investigative Sciences, West Virginia University, Morgantown, WV 26505

Field (Broad Category): Forensics (Physical Sciences & Engineering) 

Student’s Major: Forensic and Investigative Science and Chemistry 

The forensic analysis of organic (OGSR) and inorganic (IGSR) gunshot residue has been widely studied using various methodologies. Recent efforts have described identifying both components of GSR to increase the confidence of a collected sample; however, few methods allow for dual detection of IGSR and OGSR on a single instrument which when used saves time and resources. To address this, our lab developed a method using LC-MS/MS, which is available in most crime labs. Two common materials for collecting GSR from hands of individuals are polymers and carbon tape. Standard GSR practice (ASTME1588) uses carbon tape to recover IGSR analytes. However, recent studies have shown that polymer collection is possible for IGSR and OGSR due to its porosity and the OGSR lipophilic nature. Realizing this, we tested carbon tape, “Tesa Tack”, and two synthetic polymers. Each component (EC, MC, DPA, NNDPA, 2-NDPA, 4-NDPA, Ba, Pb, Sb) and a mixture of the components was deposited at 20uL at 20 ppm and extracted using acetonitrile for OGSR and an acid solution for IGSR. The intensity of response was monitored and recorded using MassHunter® Qualitative and Quantitative Analysis softwares. Hypothesis testing methods such as ANOVA was implemented to compare the efficiency of the substrates. Comparing methods, carbon tape indicated a more efficient extraction of OGSR than the “Tesa Tack.” 

Funding: National Institute of Justice 

Program/mechanism supporting research/creative efforts: WVU 497-level course