Plug-and-Play Forensic MS
Portable mass spectrometry readies itself for on-site identification of physical evidence.
Transporting, processing and finally analyzing crime scene evidence takes precious time, creating a backlog in forensic labs. Three Illinois State University professors have been working on the development and implementation of a portable mass spectrometer that could allow real-time analysis at the crime scene itself. Christopher Mulligan, Associate Professor in the university’s analytical chemistry department tells us more.
What makes your device different to other portable MS systems?
We have adapted a FLIR Systems AI-MS 1.2 cylindrical ion trap mass spectrometer, which is a ruggedized, portable MS system made for harsh environments. And we have developed ionization methods that allow one to screen forensic evidence types directly in their native state (what is commonly referred to as “ambient” ionization), yet do not require volatilization for sample introduction. It is common for many of the portable MS systems available to require samples to be in the gas-phase prior to its investigation because of their low-power vacuum systems. Systems are either limited to gas-phase analytes (for example, the KORE MS-2000) or rely on thermal desorption of the sample (for example, the M908 from 908 Devices), which can alter or complicate data.
Since the AI-MS 1.2 employs a true atmospheric inlet (that is, a directly capillary inlet from the external environment into the MS vacuum system) like traditional lab-scale MS instrumentation, it is compatible with a plethora of ionization sources that have shown promise to forensic sample analysis. So we’ve built a suite of ionization sources that can be used rapidly in a plug-and-play style. In this way, the user can select the most suitable source for the evidence at hand. Currently, we have sources that accommodate solids (for example, trace residues and bulk powders), liquids/solutions, and gases. Most importantly, these sources – as well as the whole MS system – are simple to operate and flexible so that they can be used by non-technical operators. Another distinction is that our system employs tandem MS (MS/MS) data and fragmentation spectral matching to provide a much more accurate identification of the unknown substances encountered.
A good analogy is the recent success and utility of phone applications. The portable MS itself is like a phone, which can do a few things like make calls and take photos, but the real power and utility of the device is unlocked by compatible apps (like social media, word processing, email...) Having a selection of plug-and-play style ionization sources available is analogous to having several highly useful and effective apps available at the discretion of the user.
What are the highlights from your research?
It was exciting when we tested the applicability of our system towards clandestine drug laboratory screening by actually making methamphetamine alongside US DEA representatives (1). You really get a feel for the difficult task that today’s law enforcement and crime scene investigators face when you see just how easy and rapidly it can be produced (see "Legal Highs and Lows" for more on the war against drugs). During this exercise, we showed the AI-MS 1.2 was capable of identifying both reaction precursors (for example, pseudoephedrine) and the methamphetamine product regardless of time point of the synthesis. Furthermore, our gas-compatible source based upon atmospheric pressure chemical ionization (APCI) was able to then go through and identify organic solvents utilized for extraction and drying.
How has the collaborative approach paid off?
It has been transformative. Forensic science is fundamentally an interdisciplinary field, so bringing in broad expertise allows us to investigate new areas of research. Through our recent National Institute of Justice grant funding, I have been collaborating with Jamie Wieland (ISU Department of Technology) to determine the financial viability of the system compared to current evidentiary protocols and Michael Gizzi (ISU Department of Criminal Justice) to examine the legality of using our developed method to prompt “probable cause” searching in traffic control stops. Both of these research directions would have been very difficult to pursue with just my skill set...
What are the main challenges ahead of you?
Our ultimate goal is to create a MS platform that is readily useable in both crime scene investigation and routine law enforcement scenarios. In these environments, the primary user will not be an analytical chemist, so the burden falls on us to ensure that the instrument is both easy to use, but also robust in terms of data quality when non-technical personnel operate it.
- AE O'Leary et al., “Monitoring the clandestine synthesis of methamphetamine in real-time with ambient sampling, portable mass spectrometry”, Anal Methods, 7, 7156– 7163 (2015). DOI: 10.1039/C5AY00511F
Associate Professor, Illinois State University.