New methods and standardization in chemical forensics

In her doctoral thesis completed at the Finnish Institute for Verification of the Chemical Weapons Convention VERIFIN, University of Helsinki, Solja Säde developed methods of chemical forensics.

“The goal was to promote methodological development in the field overall and to facilitate the standardization of methods,” Säde says.

The use and development of chemical weapons were prohibited under the Chemical Weapons Convention (CWC) in 1997, and the Organization for the Prohibition of Chemical Weapons (OPCW) was established to oversee this prohibition.

Chemical warfare agents have nevertheless been used, for example, in Syria in 2013–2018, in the assassination of Kim Jong-nam in 2017, in the poisoning of the Skripals in 2018 and in the poisoning of Navalny in 2020.

In addition, deployment of riot control agents occurred in Ukraine in 2024 and 2025, with Russia being suspected of the attacks, despite prohibition of the use of riot control agents in warfare by the convention.

“These events make it extremely important to develop methods of chemical forensics to determine the perpetrators responsible for using chemical warfare agents,” Säde says.

Uniform standards

“Forensic investigations can progress by analyzing the by-products, impurities, degradation products and isotope ratios of chemical samples,” says Säde.

Methods used for sample analysis include gas chromatography– and liquid chromatography–mass spectrometry, used also at VERIFIN, which is part of the OPCW laboratory network.

In real-life situations, samples are analyzed simultaneously in several OPCW designated laboratories. For the sake of validity, it is important for the laboratories to operate independently despite arriving at the same results.

Säde furthered the standardization of methods, which is aimed at making results comparable between laboratories and, consequently, increasing their reliability in potential court proceedings.

Determining the sources of substances

As part of the doctoral research, a method was developed to identify the link between chemical warfare agents and the origins of the substances used in their manufacture. The method produced compounds using starting materials purchased from different producers, and a link between a specific product and the producers of its starting materials was identified through impurity profiling and statistical multivariate classification methods.

This method can extract further important forensic information on chemical warfare agents used in any attacks.

A tool for quality control

The doctoral thesis also advanced the comparability of results obtained in different laboratories and using different methods.

During the process, a quality control sample was developed to ensure the optimal functioning of gas chromatography–mass spectrometers specifically for the purposes of chemical forensics. The sample contains compounds that measure the operating condition of the device, and the sample is tailored to chemical forensics through a broad range of compounds included in various concentrations.

The sample was also used to compare the results of 11 laboratories from around the world.

Comparing statistical classification methods

The doctoral thesis is composed of three articles. The latest will soon be published: “Comparison of statistical multivariate analysis methods for chemical forensics profiling of a carbamate chemical warfare agent precursor” (in review).

In the article, Säde and her colleagues compared statistical classification methods widely used in chemical forensics. Their reliability is important to ensure the comparability of results between different methods and laboratories.