Chromafil ptfe syringe filter

The adhesive was carefully removed from the stub with cleaned tweezers and deposited in a 20 mL scintillation vial (Sigma-Aldrich, Buchs, Switzerland) containing 1 mL of methanol (grade ULC-MS from Biosolve, Dieuze, France). The OGSR were then solubilized by sonication for 15 minutes at room temperature. Finally, the solution was filtered through 0.2 μm Chromafil PTFE syringe filter (Macherey-Nagel, Düren, Germany). Extracts were stored in the freezer at -24 °C until UHPLC-MS/MS analysis.
Additionally, to detect contamination that could occur during sample preparation, a stub was stored for 72 hours in the laminar flow hood used for the preparation and extraction of OGSR. Blank solutions were also prepared to identify contamination that may occur during the extraction of OGSR. To this end, a fraction of the methanol used as solvent was collected after the extraction of specimens.

For OGSR extraction, the carbon adhesive was removed from the stub with carefully cleaned tweezers and transferred to a 20 mL scintillation vial containing 1 mL MeOH. Then, the vials were ultrasonicated during 15 minutes at room temperature to solubilize OGSR. Finally, the resulting solution was filtered through a 0.2 µm Chromafil PTFE syringe filter (Macherey-Nagel, Düren, Germany) to remove carbon particles. In order to monitor laboratory contaminations during OGSR extraction, methanol blanks were prepared, one before starting an extraction session and one after preparation of a sequence of specimens. Likewise, a blank carbon tab was extracted to check for potential contamination of the stub batch.
To analyse gunpowders, a cartridge of each gunpowder was opened using a slide hammer. A 1 mg/mL extract was prepared using the aforementioned protocol.

Specimens were collected from 64 police vehicles in collaboration with two regional police services.
Collection was performed using carbon stubs from Plano (Wetzlar, Germany), consisting of an adhesive carbon tab 12 mm in diameter mounted on a 12.5 mm aluminium inserted in a plastic vial and sealed with a screw cap. Two stubs were collected per vehicle: the first one from the driver's seat and the second from the back seats. The stubs were dabbed about 200 times on the seats (the whole surface was sampled), following recommendations from Zeichner et al. [47] for clothing items.
For compound extraction, the carbon adhesive was removed from the stub with clean tweezers and transferred to a 20 mL scintillation vial containing 1 mL MeOH. The vial was placed in an ultrasonic bath at room temperature for 15 minutes before filtration of the resulting extract through a 0.2 µm Chromafil PTFE syringe filter (Macherey-Nagel, Düren, Germany) to remove carbon particles. To detect potential laboratory contamination during specimen preparation, methanol blanks were prepared before and after each extraction session. Likewise, a blank carbon tab was extracted to check for potential contamination originating from the stub batch. For all these control samples, no OGSR were detected.