## 3 Results and Discussion
### Real Sample Measurements  
#### 3.3.1 Shrapnel of Defused Bomb  
Besides standard substances, samples from real-world scenarios were investigated to exploit the practical capabilities for forensic analysis. For this purpose, post-blast residues of a defused Second World War bomb are investigated. This bomb was defused by controlled explosion carried out by the Berlin Police. After the explosion, shrapnel were gathered up by hand, sent to our laboratory and stored in a cardboard box at room temperature inside the laboratory. This scenario is a good example of a real world scenario where only little information about the exploded bomb is available. No further information about the bomb is available because it was defused as part of a batch of old bombs.  
Figure 3 shows the results of the investigation of one of the pictured shrapnel with the APLD system. In sum, four different shrapnel pieces were investigated and 2 to 4 locations per shrapnel measured. It turned out that all spectra exhibit a clear signal at \(m/z\) 227, which can be correlated to the molecular ion signal M\({}^{-}\) of TNT. The presence of TNT can be assumed by the observed signals in the lower mass spectrum including the molecular ion signal of TNT at \(m/z\) 227, as well as two significant signals of respective fragments. As a comparison, the embedded mass spectrum shows an additional measurement of a 10 ng TNT standard sample measured under the same conditions. As can be observed in the mass spectrum, strong indications of TNT attached to the bomb shrapnel were found. In addition, fragmentation seems to be caused by the substrate. Therefore, results confirm that the APLD measurement system is not only suitable for laboratory measurements but also for answering realistic forensic questions. The APLD delivers valuable information about the used explosive,  
Moreover, even longer periods between the collection of samples and the related investigation seem to be acceptable.  
\begin{table}
\begin{tabular}{c c c} \hline \hline
**Substances Measured at Novel Systems** & **LOD** & **Structure** \\ \hline \hline
**Explosives** & & \\ \hline PA (picric acid) & 15 ng & \\ \hline
3,4-DNT & 3 ng & \\ \hline TATP (triacetonetriperoxide) & 800 ng & \\ \hline AN (ammonia nitrate) \({}^{\ast}\), \(m/z\) 63 & 78 ng & \\ \hline
**Drug precursors** & & \\ \hline Safrole & 100 ng & \\ \hline Phenylacetone & 50 ng & \\ \hline
**Drugs/drugs of abuse** & & \\ \hline Amhetamine & 20 ng & \\ \hline Methamphetamine & 10 ng & \\ \hline MDMA (3,4-methylenolixy-methamphetamine) hydrochloride & 20 ng & \\ \hline Heroin & 200 ng & \\ \hline Cocaine hydrochloride & 17 ng & \\ \hline Ketamine hydrochloride & 6 ng & \\ \hline \hline \end{tabular}
\end{table}
Table 2: Limit of detection for different individually determined drug precursors, drugs, drugs of abuse, and some additional explosives measured with the novel APLD system. It is mutually assumed that the amount of substance is to be seen as a total amount and the sample spot is considered as totally desorbed at the measurement as described in the materials and methods section. Substances that have been detected as fragments are marked with an * along with the \(m/z\) fragment value. All explosives were detected as molecular ion signals and all other substances as protonated molecular ions. All explosives were measured in negative detection mode, all other substances in positive detection mode.