# Chemical Analysis of Gunpowder and Gunshot Residues
## 3 Analysis of Gunpowder and Gunshot Residue
### Liquid Chromatography  
Liquid chromatography (LC) is a highly sensitive and reproducible technique commonly used in forensic sciences. It is suited for separating non-volatile, semivolatile, and thermolabile compounds and can be combined and/or coupled with a wide range of detectors, conferring high flexibility to the technique [14; 126]. However, LC has several limitations, such as extensive sample preparation for some applications, large consumption of organic solvents, and its destructive nature with regards to the probative value of the sample (depending on the detector used) [15; 18]. Nonetheless, several works have already explored the use of LC coupled with MS [18; 37; 56; 57; 68], diode array detector (DAD) [127; 128], and ultraviolet (UV) [16; 54] detectors for forensic ballistics (Table 2). \begin{table}
\begin{tabular}{c c c c c c} \hline
**Technique** & **Objectives** & **Target Analytes** & **Matrix** & **Conclusions** & **Ref.** \\ \hline \multirow{4}{*}{\begin{tabular}{c} Surface-enhanced \\ Raman scattering \\ (SERS) \\ \end{tabular} } & \begin{tabular}{c} Development of a \\ new analytical \\ procedure for fast \\ and sensitive \\ analysis of GSR \\ \end{tabular} & GSR & \begin{tabular}{c} GNPowder and \\ GSR solutions \\ \end{tabular} & \begin{tabular}{c} Detection of several \\ compounds, mainly EC, \\ DPA, and its derivates \\ \end{tabular} & [99] \\ \hline \multirow{4}{*}{\begin{tabular}{c} Micro-Raman \\ spectroscopy; \\ SLA-ICPMS \\ \end{tabular} } & \begin{tabular}{c} Detection and \\ identification of \\ GSR compounds \\ (IGSR and OGSR) \\ \end{tabular} & \begin{tabular}{c} OGSR \\ (micro-Raman); \\ IGSR (SLA-ICPMS) \\ \end{tabular} & \begin{tabular}{c} Tape-lift \\ (modified) \\ \end{tabular} & \begin{tabular}{c} Capable of detecting GSR \\ from shooters’ hands \\ \end{tabular} & [120] \\ \hline \multirow{4}{*}{\begin{tabular}{c} Raman and LIBS \\ \end{tabular} } & \
\begin{tabular}{c} Differentiate OGSR \\ samples from \\ ammunition types \\ of the same \\ manufacturer \\ \end{tabular} & OGSR &
\begin{tabular}{c} Aid in the identification \\ and characterisation of \\ GSR components \\ accurately \\ \end{tabular} & [125] \\ \hline \end{tabular}
\end{table} 
Table 1: _Cont._ \begin{table}
\begin{tabular}{c c c c c c} \hline
**Technique** & **Objectives** & **Target Analytes** & **Matrix** & **Conclusions** & **Ref.** \\ \hline \multirow{4}{*}{\begin{tabular}{c} LC-MS/MS; \\ SEM-EDX \\ \end{tabular} } & \begin{tabular}{c} Separation and \\ detection of both \\ IGSR and OGSR in \\ the same sample \\ \end{tabular} & GSR & \begin{tabular}{c} GSR solution (in \\ methanol and \\ acetonitrile) \\ \end{tabular} & \begin{tabular}{c} Development and \\ validation of the \\ methodology \\ \end{tabular} & [37] \\ \hline \multirow{4}{*}{\begin{tabular}{c} UPLC/MS/MS/MS \\ \end{tabular} } & \begin{tabular}{c} Separation and \\ detection of OGSR \\ compounds \\ SG \\ \end{tabular} & \begin{tabular}{c} Organic \\ components from \\ SG \\ \end{tabular} & \
\begin{tabular}{c} GNPowder \\ solutions (in \\ methylene \\ chloride) \\ \end{tabular} &
\begin{tabular}{c} Separation and \\ the authors, this \\ procedure allows the \\ differentiation between \\ brands and lots by \\ analysing the \\ compounds. According to \\ the authors, this \\ procedure allows the \\ differentiation between \\ brands and lots by \\ analysing the \\ compositional differences \\ \end{tabular} & [28] \\ \hline \end{tabular}
\end{table} 
Table 2: Summary of some LC techniques employed in GSR analysis. [PERSON] et al. [25] used ultra-high-performance LC (UHPLC) coupled with tandem mass spectrometry (MS/MS) to evaluate the simultaneous analysis of ISGR and OGSR. The authors evaluated the latter by analysing eight organic compounds commonly found in gunpowder (NG, DPA, AK II, EC, 4-nDPA, 2-nDPA, 2,4-DNT, and N-n-DPA) to compare three sampling procedures. With a similar goal, [PERSON] et al. [30] used UHPLC-UV-MS/MS to develop and compare collection techniques for both OGSR and IGSR.