Forensic scientists receive over a million requests for seized drug analysis in the United States each year, and the number is steadily climbing. The proliferation of novel psychoactive substances in recent years, including synthetic opioids and cannabinoids, has certainly contributed to these rising numbers. As a result, researchers are searching for improved ways to evaluate their drug samples for more swift evidence processing.
Direct Analysis in Real Time Mass Spectrometry (DART-MS) can determine sample composition from solid, liquid, or gaseous compounds nearly instantaneously, and has garnered recognition as a suitable technique for the rapid analysis of emerging drugs. The technique has even been successful when low concentrations of the drug are present, relative to the cutting agents. One apparent drawback to the forensic application of DART-MS, however, has been the difficulty associated with data processing and interpretation of complex drug mixtures. The commercial software that is currently available for mixture analysis can only indicate if a compound of interest is present or absent, not generate probabilities, and is designed for field-based instruments rather than those typically used in forensic laboratories.
See the Sidebar “What is a Mass Spectrum?”
NIJ-funded researchers from the National Institute of Standards and Technology (NIST) created an automated data evaluation process, developing and releasing a DART-MS mixture interpretation software program that is free, flexible, vendor agnostic, and open-source. The researchers sought to develop a suite of tools to analyze complex DART-MS spectra rapidly and reliably, easily create or amend spectral databases, identify unknown substances, and generate reports using their Data Interpretation Tool software.
Software Development, Evaluation, and Deployment
Underpinning the software is a search algorithm created by the researchers specifically for the analysis of DART-MS data. The researchers used a novel technique to provide a probabilistic value of a drug’s presence or absence in a sample by combining data from low-voltage DART-MS (low fragmentation spectra) with DART-MS data produced from increasing voltage (higher fragmentation spectra).
In their software development, they sought to determine the necessary features, documentation, and training tools needed by researchers in the field. Specifically, they outlined three objectives:
- Develop an intuitive user interface and training manual.
- Evaluate the software, with feedback from local, state, and federal forensic laboratories.
- Deploy the software to the community.
Accomplishments and Expected Applicability
By achieving their established objectives, the researchers hoped to harness the powerful data produced by DART-MS to allow drug chemists to interpret mass spectra more easily, accurately, and confidently. The Data Interpretation Tool simplifies report generation and provides a freely available platform for data analysis. It offers labs a means to:
- Interpret mixture spectra in complex drug samples.
- Utilize the NIST DART-MS spectral databases.
- Easily generate informative reports.
The Data Interpretation Tool isn’t solely limited to the analysis of seized drugs. With the establishment of a relevant spectral library, the researchers outline other possible uses, most notably for the study of trace evidence, ignitable liquids, and toxicology. Since it is open-source, researchers are hopeful that the software can be extended and modified to suit other uses in the forensics community and beyond.
Scalability and Program Size
While the software provides a novel, highly useful addition to the arsenal of complex drug mixtures analysis, researchers acknowledge a few notable limitations. At present, scale-up studies have not yet been conducted, so it is unclear how the program will perform with larger datasets, larger spectral libraries, or significantly altered search algorithms. Moreover, the final program size is quite large (approximately 300 MB), which could be cumbersome for some end users.
Nonetheless, feedback on the application has generally been extremely positive, with one user’s review exclaiming, “I love it!!! There is so much information for each entry – having the structure, chemical formula, exact mass, and synonyms right there is very helpful. The expanded view and report printing capabilities are wonderful. This is ready for prime time!!! I would give it an 11/10.”
About This Article
The work described in this article was supported by NIJ award number DJO-NIJ-20-RO-0012, awarded to the National Institute of Standards and Technology.
This article is based on the grantee report “Development of an Open Source Direct Analysis in Real Time Mass Spectrometry (DART-MS) Search Software and Library Building Tool for the Analysis of Complex Drug Mixtures” (pdf, 18 pages), by Edward Sisco, Arun Moorthy, Ruthmara Corzo, and Stephen Tennyson.
Sidebar: What is a Mass Spectrum?
Various types of ions are produced when molecules are ionized in a mass spectrometer. A Mass Spectrum is a graphical representation of the mass distribution of the ions. From the mass spectrum, we can obtain information about molecular weight and molecular structure and identify unknown samples.