Application of a Modified 3D-PCSI-MS Ion Source to On-Site, Trace Evidence Processing via Integrated Vacuum Collection

Abstract

Trace evidence, including hair, fibers, soil/dust, and gunshot residue (GSR), can be recovered from a crime scene to help identify or associate a suspect with illegal activities via physical, chemical, and biological testing. Vacuum collection is one technique that is employed in recovering such trace evidence but is often done so in a targeted manner, leaving other complementary, chemical-specific information unexamined. Here, we describe a modified 3D-printed cone spray ionization (3D-PCSI) source with integrated vacuum collection for on-site, forensic evidence screening, allowing the processing of targeted physical traces and nontargeted chemical species alike. The reported form factor allows sample collection, onboard extraction, filtration, and spraybased ionization in a singular vessel with minimal handling of evidence by the operator. Utilizing authentic forensic evidence types and portable MS instrumentation, this new method was characterized through systematic studies that replicate CSI applications. Reliability in the form of false positive/negative response rates was determined from a modest, user-blinded data set, and other attributes, such as collection efficacy and detection limit, were examined.

Criticality of Spray Solvent Choice on the Performance of Next Generation, Spray-Based Ambient Mass Spectrometric Ionization Sources: A Case Study Based on Synthetic Cannabinoid Forensic Evidence

“…All mass spectral data in this work were collected using a FLIR Systems AI-MS 1.2 cylindrical ion trap (CIT) mass spectrometer (FLIR Mass Spectrometry, West Lafayette, IN, USA). We have reported the use of this portable MS system coupled with ambient ionization methods previously [9,23,[27][28][29][30]34]. This instrument features a weight (~45 kg) and overall dimensions (60 cm × 50 cm × 40 cm, LWH) that are well-suited for field-based applications.…”

“…The field of ambient ionization has also grown to include "substrate spray" techniques, where materials are used for sample holding/collection and the ionization medium, including techniques like paper spray ionization (PSI) [25], sandpaper spray ionization (SPS) [26], filter cone spray ionization (FCSI) [27], and, more recently, 3D-printed cone spray ionization (3D-PCSI) [28,29], which utilizes additive manufacturing to produce electrically conductive vessels from carbon nanotube-infused filaments. Many of these ionization methods have also been demonstrated on portable MS systems [23,[29][30][31][32][33][34], further increasing the overall sample throughput by offering "on-demand" sample screening.…”