Thought Leaders

Chemical Clues: Real-time Forensic Analysis of Drugs and Explosives

Thought LeadersArian van Asten Professor in Forensic Analytical ChemistryUniversity of Amsterdam

In this interview conducted at Pittcon 2024 in San Diego, we spoke to Professor Arian van Asten about advancements in the chemical analysis of drugs and explosives using portable NIR spectroscopy and its significant impact on improving on-scene investigation methods for law enforcement agencies.

Could you please introduce yourself and discuss what led you to focus on the chemical analysis of drugs and explosives within forensic analytical chemistry?

My name is Arian van Asten. I am a professor of forensic analytical chemistry at the Van 't Hoff Institute of Molecular Sciences of the University of Amsterdam. Before that, I worked for a long time at the Netherlands Forensic Institute.

I have a PhD in analytical chemistry and a passion for forensic science. I am involved in many different projects focusing on a wide array of evidence materials and analysis methods, but my special interest is in the analysis of drugs and explosives. What makes them special is that these chemicals are directly related to certain types of crimes.

Could you briefly describe the main challenges that law enforcement agencies face in some on-scene chemical identification of drugs and explosives that are being used in these crime scenes?

Starting with illicit drugs, the US is in the midst of the opioid crisis. This translates to forensic experts seeing an increasing number of cases. The caseload is very high, and the chemical complexity of the samples requiring analysis has also increased. It is more difficult to analyze them correctly.

With respect to explosives, this is a challenging area because of the chemical diversity that is encountered. You have organic and inorganic materials, so typically, one single analytical technique does not suffice in a given case.

In addition, there are cases in which intact explosives are present, which we call pre-explosion cases, and cases after an explosion. These two settings yield completely different samples to analyze.

Image Credit: PowerUp/

How does your research address some of these challenges?

The work that I presented at the Pittcon Conference allows people to conduct chemical analysis in the field using portable technologies that do not require high-end laboratory conditions.

This is focused explicitly on rapid chemical identification of drugs and explosives with operators who do not need a chemistry background. I try to advance forensic analytical chemistry in this way.

As a forensic or analytical chemistry expert, I think the challenge is to create a methodology that allows non-experts to do complex chemical analyses themselves in a simple and error-free manner. If measurements fail because controlling the instrument is too complicated, then we have to make it simpler! This would ultimately allow law enforcement professionals to identify drugs and explosives robustly and instantly.

What led to the selection of near-infrared (NIR) spectroscopy as the primary technology for your research, and how does it compare to other portable analysis technologies? 

There are several options or routes that you can consider, such as mobile mass spectrometry, electrochemistry, and colorimetric reactions. Then, there are several spectroscopic methods to consider: Raman, infrared, and near-infrared. We chose near spectroscopy, as it lends itself very well to miniaturization. You can have very small, almost pocket-sized, near-infrared spectrometers, and they are extremely rapid. Using the technology we work with, you record a reflectance spectrum in a few seconds.

When people talk about rapid analysis, they sometimes introduce methods that take a few minutes. If you talk to professionals who operate within law enforcement or customs, a few minutes on the scene doing a measurement can feel like a lifetime. That makes near spectroscopy very attractive. Within 10 to 20 seconds, I can do multiple measurements on the same sample.

How does the miniaturized MEMS NIR sensor integrate with existing law enforcement procedures for drug and explosive detection? What are its key advantages? 

For illicit drugs, for example, the first step in the field is often a colorimetric reaction. This is challenging because people in the field have to add liquids to a sample to observe color, and they are not necessarily trained to do so.

We use reflectance sensors, where people simply place a glass vial with a small amount of powder directly on the sensor, and then press scan. There is no sample preparation, no complex instructions. This is a very convenient process both in the field and in a laboratory situation where you are carrying out high-volume screening.

Pittcon Thought Leader: Arian Van Asten

Can you elaborate on the dedicated data analysis strategy you have developed, particularly the role of Linear Discriminant Analysis (LDA) and Net Analyte Signal (NAS) in improving accuracy? 

Credit is due here to Dr. Henk-Jan Ramaker from TIPb. He did and does a lot of the model development and the chemometrics (advanced data analysis).

This is also where one of the technique's challenges comes in. Imagine you are in a forensic setting, and you have a sample with an unknown composition. You have an idea that it could contain explosives or illicit drugs, depending on the context of the case, but you are not sure. The sample is also not pure.

A typical street sample of a drug can contain several other substances in addition to the psychoactive substance of interest. This includes adulterants, diluents, or tableting agents. When taking a measurement, you will get a composite signal with spectral features of all these components. So here, we need data science to help us decipher the complex signal and tell us what compounds are present and at what level.

You can take a machine learning approach, but that typically requires huge amounts of data. We can measure thousands of street samples, for which we have used other techniques like GC-MS to determine the composition. We use that knowledge to look for similar signals if we have an unknown and suggest its composition.

What Dr. Ramaker has developed is much more elegant. He takes pure compound spectra of all the known possible constituents in a sample for a given type of drug. With this limited set of spectral reference data, he subsequently 'explains' the observed signal. This is much faster and requires less reference data for a functional model. You, for instance, only need the NIR spectra for 10-15 pure compounds to fit all cocaine street formulations.

Have you noticed an increase in complexity in samples over time, or do you think the instruments are getting better at characterizing the large variety of compounds that are in a sample?

I think both are true. We have more analytical capability to look at very low levels of substances within samples and chemically understand what is going on.

Chemical profiling is a different field that I am involved in. Here, we look at how materials are degrading and what kind of raw materials are used. We are interested in impurities and what they tell us about how the material was made or transported. You cannot typically do that with portable spectroscopy. The technique is not sensitive enough. Compounds need to be present at 5-10 wt% to be 'noticed'.

It is also true that the chemical complexity of illicit drug case samples has increased considerably. There are two reasons for that.

First of all, because many countries work with lists of banned substances in their illicit drug legal framework, we have seen 'creative' criminals producing so-called new psychoactive substances (NPS). These designer drugs look and function very similar to their banned analogs but are not listed and, therefore, do not fall under the illicit drug law. Selling such a product is consequently not an illicit drug crime.

Governments tend to react when they see such new materials entering the illicit drug market. They take legal action to place the new compound on the list of banned substances. But that fuels a rat race in which the criminal makes another variant when the ban is successful. We have seen a rise in what we call designer drugs in many European markets. Meanwhile, there is an additional challenge here in the US where the ongoing opioid crisis is leading to drug street samples that contain multiple fentanyl analogs at relatively low levels in the presence of cocaine or heroin.

Do you find there is a lot of open communication between governmental organizations and researchers in your field conducting research into these different chemical profiles?

I think there is. The forensic science domain is open, but it is also a somewhat complex situation. We are scientists, so we would like to explore new methods, develop them, and share them to contribute to a safe and just society. But at the same time, there is always the risk that this information falls into the wrong hands. This is especially important when you investigate how to make explosives or how to characterize drugs of abuse.

Additionally, forensic science is typically a very international, open environment where people are eager to share, whereas criminal justice is typically more closed, domestic, and local. This makes it for instance difficult and rare to bring in foreign forensic experts to report and testify in a case. This is also understandable, crime is a sensitive and typically a national affair with local victims and perpetrators. 

How close are the current technologies to meeting the standards of forensic evidence admissible in court, and what are the main problems that need to be addressed to achieve that goal?

There are a couple of problems here. First of all, when you transition from science and innovation to something used in forensic practice and being presented as forensic evidence in court, you need to be very strict with respect to quality. You need validation studies and accredited methods. You have accreditation bodies that come and check to make sure that 'you say what you do and do what you say.'

So you need to make that new method fit for purpose. You would have to show, quite vigorously, that you know the error rates, you know when things go wrong, you know how to spot an error and how to improve. This is very important because once that evidence is in court, it can have a lot of impact, especially when drugs or explosives are involved. You need it to be free of error.

Of course, where work is done, errors are made; this is inevitable. But in a forensic setting, you need to show that you have minimized and mitigated potential errors and that you have a system in place to spot errors, correct them, and prevent them from happening in the future. Forensic evidence can make a lot of difference to the people involved, including suspects, victims, and family members, and therefore, must be of superior quality.

However, there is also the interesting question of when a forensic investigation is good enough. When is there enough selectivity to say that, with a portable technique, you can do a measurement in seconds and also present the findings with confidence in court? Here, as a forensic scientist from academia, you can run into some conservatism and resistance. People tend to rely on what they trust and have been using successfully in the past. However, these trusted methods were once also highly innovative and groundbreaking!

To what extent can we depend on science to give us the facts?

There is a clash here. If you are in court, then the judge, the people involved, the public prosecutor, and the legal defense all have a very simple question. Did that person fire the gun? Did the suspect produce these cocaine samples? However, forensic scientists and experts need to take scientific uncertainty into account. When the expert involved tries to explain this uncertainty, everybody starts to think, "You are the expert. Why are you telling this difficult story? The question was very straightforward; just say yes or no based on your expertise and experience". This is why forensic scientists and experts must also be great communicators, being able and willing to explain difficult scientific aspects in a simple yet convincing manner.

Could you discuss the collaborative nature of this project with the Dutch Police, TIPb, and other partners? 

Collaboration is essential to developing such a methodology and successfully introducing it in forensic practice. For a lot of the research I do, I arrange a 'triangular collaboration' involving academia, commercial companies, and users. I need forensic practice because they need to tell me how an investigation is conducted and the problems and challenges they face. They can also supply me with samples from actual cases rather than artificially created samples. These are really valuable samples on which to test and develop the methodology.

At the same time, we need companies and technology to realize our ideas and develop viable and robust instrumentation. A very powerful method may exist, but the research group involved is often not capable of taking the next step and developing a product that could really make a difference. Many innovations fail because of this. Involving a company that is able to develop, introduce, and maintain a product is the magic ingredient that you need to be successful.

In practical terms, how easy would you say it is for law enforcement personnel to use the near-infrared-based platform we discussed earlier? Is there any training that is currently needed to use it?

Basic instruction would suffice. It is very simple. You have the platform. You take the PowderPuck, a small portable benchtop, and put it on the table. You take a glass vial, put in 0.5 to 1 gram of a powder sample, put it on the instrument, and press scan. That is it. I think a 5-year-old child could get it right.

How does your presentation at Pittcon contribute to the broader conversation about technological advancements in forensic science?

I have attended several of the National Institute of Justice (NIJ) sessions here. You hear a lot about forensic science and the advancements in several areas, but there is clearly a lot of interest in portable technology and bringing that analytical technology out of the lab and into the field.

When you go out here on the exhibition floor, there is an interesting transition ongoing in terms of not just technology being presented but also computing possibilities. This allows you to create products that transfer data wirelessly, get results on your mobile phone, and connect to central servers where powerful computers carry out complex data analyses and send results back to the user. I think that we will see many more of these types of developments opening up a whole range of possibilities.

Years ago, you would go into the field with a Raman instrument, and everything would have to take place on that single instrument. But this limitation does not exist anymore. Now, you can take the measurements, send the data to a central location, and share it with other users.

Experts can also examine the data from a distance and perform a quality check on the data in seconds. To the user, this seems almost instantaneous as results appear on the smartphone or tablet. But in the mean time a lot is actually happening 'under the hood'. I think that these data science developments will revolutionize analytical chemistry.

What are you most looking forward to at Pittcon San Diego this year?

The presentations and meetings with scientists are nice, but I think what makes Pittcon very special is the exhibition. It is massive! There is no equivalent to that in Europe or the Netherlands, and I find that very inspiring.

There is all this energy and activity, particularly when it comes to analytical chemistry. It is never only the science, right? There must be instrumental and technological developments to back it up and really make a difference, and that is what you see on the expo floor.

As we mark the 75th anniversary of Pittcon this year, could you share your first memory or experience of attending this conference and how it has impacted your view of the scientific community?

The first time I attended Pittcon was in 2014 in Chicago, and again in 2017. When you go out on the expo floor for the first time, it is mind-blowing. I had never seen anything like that before, even having been an analytical chemist for many years. You get this feeling of really getting into it, talking to people, touching instrumentation, and hearing about great ideas.

It is inspirational to see other types of applications that can trigger questions like, "Oh, what would the forensic angle be here? Could it be useful? Could I use this to solve a crime?" Then you start talking to people. Some of the projects that I am involved with have actually emerged from these types of discussions.

About Arian Van Asten

Arian van Asten is a full-time professor in forensic analytical chemistry and on-scene chemical analysis at the van ‘t Hoff Institute for Molecular Sciences, Faculty of Science, University of Amsterdam. His research interests include the chemical profiling of explosives and drugs, the analysis of (bio)markers of CWA (Chemical Warfare Agent) exposure, rapid chemical identification at the crime scene with portable instruments, the forensic use of comprehensive 2D chromatography, chemical imaging of forensic traces, and the use of data science and A.I. to generate forensic chemical intelligence from large volume forensic case data. In addition, he is the director of the Master Forensic Science at the Institute for Interdisciplinary Studies of the University of Amsterdam, the only 2-year full-time MSc program in forensic science in the Netherlands. Together with prof dr Maurice Aalders he leads the Co van Ledden Hulsebosch Center (CLHC), a national forensic network organization named after the first Dutch forensic science pioneer. Prior to his transfer to the University of Amsterdam in 2018, he worked for over 12 years at the Netherlands Forensic Institute as a member of the management team, department head, manager of R&D programs and forensic coordinator of complex, international cases, including bomb attacks and airplane crashes. He has (co)authored over 80 peer-reviewed scientific publications on (forensic) analytical chemistry and is the author of the academic course book ‘Chemical Analysis for Forensic Evidence’ that was published at the end of 2022. 

This information has been sourced, reviewed and adapted from materials provided by Pittcon.

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