Smokeless powders can be vital aspects of forensic investigations, though distinguishing between different powders can prove difficult. Chinese researchers aimed to simplify this process using gel permeation chromatography.
To better identify different smokeless powders (SLPs) in forensic investigations, researchers from the Ministry of Public Security in China used gel permeation chromatography (GPC) to characterize different SLP properties. Their findings were published in the Journal of Chromatography A (1).
Smokeless powders (SLPs) are propellants used in firearms and artillery that produce negligible amounts of smoke when fired (2). In China, they are the most common low explosives used to create improvised explosive devices (IEDs), such as pipe bombs and home-made ammunition. SLPs are commonly encountered in the investigation of many firearm- and explosive-related crimes, making their examination, analysis, and profiling very important from a forensic perspective. A common practice in forensic investigations is to compare SLPs used in devices to those available in suspects’ houses or manufacturing places. This can help investigators establish a link between two different SLPs seized at different locations.
Major classes of compounds in SLPs include energetics, stabilizers, and flash suppressors, among others. Smokeless powders can have up to three bases, with each powder containing some degree of nitrocellulose, a type of cellulose derivative (3). Chromatography, infrared spectroscopy, and mass spectroscopy have been commonly used for the determination of different ingredients in smokeless powders; these techniques disregard the main components of NC, instead identifying the additives in SLPs.
In this study, the weight-average molecular weights (Mw), number-average molecular weights (Mn), and polydispersity index (PDI) values of 79 propellant samples were measured using GPC, with the likelihood ratio evaluation method being used to facilitate data interpretation. This technique has been useful for polymer material analysis, though few papers have reported NC analysis by GPC. The likelihood ratio (LR) evaluation method was applied to facilitate data interpretation, and the possibility of using these methods to make comparisons between smokeless powders was explored.
The inter-day precision for Mw, Mn, and PDI of samples s1, s38, and s63 was 0.052%, 0.295% and 0.368%. The intra-day precision was 0.095%, 0.457%, and 0.579%, which demonstrated that the GPC method had good reproducibility. Several SLP samples were analyzed using GPC. As a supplementary method of discriminating and individualizing SLP samples, GPC made full use of NC’s main components, regardless of what kind of propellants were studied; this provided further information, as opposed to only focusing on the additives within them. Mw, Mn, and PDI information played a significant role, especially in cases where the additives of compared SLP samples were the same. This method, which combines Mw, Mn, and PDI measurement by GPC and LR evaluation was successfully used in real case sample comparisons with satisfying results.
Mw and PDI information proved valuable for discriminating smokeless powders from different sources, which was a helpful reinforcement to SLP commonplace analysis. Pairwise comparisons of 79 SLPs from different manufacturers and batches using LR computations gave no positive or negative misleading results. Overall, it was found that GPC, when combined with LR calculation, can be a promising means of discriminating between smokeless powders.
(1) Guo, H.; Wang, P.; Hu, C.; Mei, H.; Li, Y.; Zhu, J. Forensic Comparison Analysis of Smokeless Powders by Gel Permeation Chromatography and Likelihood Ratio Evaluation Methods. Forensic Sci. Res. 2024, 10 (2), owaf005. DOI:
(2) Smokeless Powder. Old Dominion University 2007.
(3) Li, A.; Wang, Y.; Deng, L.; Zhao, X.; et al. Use of Nitrocellulose Membranes as a Scaffold in Cell Culture. Cytotechnology 2012, 65 (1), 71–81. DOI:
Join the global community of analytical scientists who trust LCGC for insights on the latest techniques, trends, and expert solutions in chromatography.
