The Chair of Analytical Chemistry at University of Tartu

ICNTS25 – Gathering people without targets!

Having no predefined targets in your sample isn’t always a drawback. The International Conference on Non-Targeted Screening (ICNTS) demonstrated how omitting targets in mass spectrometry analysis can reveal a broader and more nuanced picture of the chemical space.

From October 13-16, for the fifth time, non-targeted screening experts from around the world gathered in Erding, Germany, to share their latest research and exchange ideas. The event showcased cutting-edge developments across diverse fields, including metabolomics, foodomics, water analysis, harmonisation, and prioritisation.

Representing our group, Pilleriin Peets, Principal Investigator of the Chemical Space & Omics group, gave an oral presentation on compound class vectors for comparing metabolomics samples. Her talk was part of the computational mass spectrometry session, chaired by Emma Schymanski, who also gave a keynote on “Data Handling in a Modern NTS World.”

The ICNTS once again proved that by embracing the unknown, researchers are expanding the boundaries of chemical analysis and opening new doors for discovery. Whether in environmental science, health, or food safety, the power of non-targeted approaches lies in their ability to reveal what we didn’t even know to look for.

Learn more about the conference and the community: https://afin-ts.de/icnts25/

Indrek Saar, PhD

On the 27th of August, Indrek Saar successfully defended his great innovation-based dissertation „Development of novel on-site chemical analysis tests – from alternative materials and technologies to functional prototypes”.

With his opponent Prof. Nicole Pamme, who is focused on Lab-on-a-Chip devices, they gave a memorable and enjoyable PhD defence at the Institute of Chemistry. Prof. Nicole Pamme holds a chair in Analytical Chemistry at Stockholm University. During the defence, her excellent general science-to-market questions, as well as detailed questions specific to chemistry and material science, helped the audience to gain a clear understanding of the need for research, practical applications and how everything was also achievable from a technological perspective.

Indrek’s dissertation has given valuable new insights into the simple to use on-site chemical analysis tests.

Picture of the fully assembled Biotin test developed in this work.

What if advanced chemical testing could be done anywhere – right where the need arises, without a laboratory?

Traditional high-quality chemical analyses often require complex equipment, trained personnel, and significant time, creating a need for faster, more accessible solutions. In Indrek`s thesis, new on-site chemical analysis tests were developed that not only simplify testing but also aim to achieve higher analytical performance than existing portable methods. These tests were developed using a novel screen-printed particle-based method that is fast, low-cost, and potentially scalable for mass production.

The applications of functional prototypes included monitoring biotin levels in urine and measuring different metal cations in various water samples, even in challenging agricultural nutrient solutions containing strong chelating agents.

Separation of biotin and its metabolites on the printed microfluidics chip. The chip has been visualised by spraying it with a solution of p-dimethylaminocinnamaldehyde (p-DACA) in ethanol and sulphuric acid.

These patented innovations are laying the foundation for highly capable, mass-producible diagnostic tools that can enable faster, more accurate decision-making in environmental monitoring, healthcare, and agriculture.

During his PhD studies and research, Indrek was supervised by Dr Hanno Evard and by Prof. Ivo Leito. Indrek’s special thanks go to the main supervisor, Dr Hanno Evard, who had been a constant source of guidance, encouragement, and support. From countless discussions and brainstorming sessions to planning and problem-solving, Hanno’s insight and commitment had been central to this work.

A Smooth and Memorable Defence

On the 27th of August, Marta-Lisette successfully defended her dissertation “Exploring the basicity of phosphanes and related compounds”, marking an important milestone in her academic journey. Her dissertation has given valuable new insights into the basicity and preparation of phosphanes and related compounds. The defence was conducted in an atmosphere of professionalism and collegiality, with a thoughtful exchange of ideas and perspectives.

Special thanks go to the opponent, Dr Martin Smith from Loughborough University, whose insightful and well-chosen questions guided the discussion. His role helped ensure the defence was not only rigorous but also smooth and engaging.

It was a proud moment for Marta (and her supervisors) and a wonderful occasion for everyone who has supported her throughout this process. Congratulations to her on this achievement!

9000 Quality-evaluated pKa values of more than 5000 acids in 7 dipolar aprotic solvents!

More than 9000 quality-evaluated pK_a values of more than 5000 acids in 7 dipolar aprotic solvents (DMSO, MeCN, DMF, pyridine, acetone, propylene carbonate and THF) have been collected from around 800 original works and are now available as an IUPAC technical report Acid dissociation constants in selected dipolar non-hydrogen-bond-donor solvents. Pure and Applied Chemistry. 2025, https://doi.org/10.1515/pac-2024-0276. The widest possible selection of compound classes is covered (Table below). The results of this large-scale pK_a data collection and evaluation work are now available for the scientific community to use in reaction mechanism analysis and modelling, catalyst design, computational method development, etc.

Very importantly, the collected pK_a data have been critically evaluated based on predefined quality criteria and depending on situation, kept as they were originally published, flagged as doubtful/unreliable (around 2700 values) or corrected (around 2500 values) (Figure above).

To enable automated processing and data mining, as well as other kinds of cheminformatics, the data are presented as a set of spreadsheets, together with structural codes (SMILES and InChI strings), compound class qualifiers and comments.

The published IUPAC Technical Report contains also comprehensive educational background information on the acid-base processes in non-aqueous media, as well as brief descriptions of the main measurement methods, with focus on the reliability of the data and sources of uncertainty.

The data collection has been deposited in the Zenodo repository and is freely available at https://doi.org/10.5281/zenodo.12608876.

The work has been carried out in the framework of the IUPAC project 2015-020-2-500. It was additionally funded by numerous sources, most importantly the EMPIR programme (project 17FUN09 “UnipHied”, www.uniphied.eu), by the Estonian Research Council grant (PRG690) and by the Estonian Ministry of Education and Research (TK210).

Unified pH (pHabs) measurements support electrocatalysis research!

In a recent publication Universal Reversible Hydrogen Potential for Electrocatalytic Ammonia Splitting Reactions in Nonaqueous Solvents from Unified pH Measurements. Inorg. Chem. 2025, https://doi.org/10.1021/acs.inorgchem.5c02177, jointly with colleagues from Michigan State University, we have used careful pH_abs measurements of dilute NH₄⁺/NH3 buffer solutions in four nonaqueous solvents – acetonitrile (MeCN), Tetrahydrofuran (THF), dimethylformamide (DMF), and propylene carbonate (PC) – to determine the pH_abs^H2O values aligned to the aqueous pH scale (see the resulting pH_abs “ladder” in the graph below). From those measurements (combined with some other experiments) it was possible to determine the reversible hydrogen potential E°_H+/H2 in these four solvents relative to the aqueous standard hydrogen electrode (SHE) and, most importantly, ensuring comparability across the different solvents. As an independent method, Open Circuit Potential measurements were carried out in the same solvents titrated with NH₄⁺/NH₃ to obtain alternative values for the reversible hydrogen potential in these solvents. The results of the two methods agreed well.

The reversible hydrogen potential values were then used to obtain, for the first time, the overpotential for ammonia oxidation as a function of solvent, with a recently discovered ruthenium catalyst. I.e., it is now for the first time possible to rigorously compare the oxidation process of NH₃ to N₂ between different solvents!

This work is a clear demonstration of the usefulness of the unified pH (pH_abs) concept in understanding and modelling electrocatalysis processes!

Many thanks, Jaan for performing the extremely difficult pH_abs measurements, Agnes for leading this pH_abs/electrocatalysis topic in our group and Michigan colleagues for the great collaboration!

Publication: Derivatization for success

Recently, a tutorial review was published in Analytica Chimica Acta by Riin Rebane and Ivo Leito, named Derivatization for success: a tutorial review of liquid chromatography mass spectrometry method optimization for determining amino compounds. Read next what Riin has to say about the review.

“This comprehensive review brings together technical depth and years of personal lab experience, shaped by long hours at the bench, countless peer discussions, and valuable lessons learned along the way. It offers a detailed, practice-oriented guide to how derivatization can dramatically improve analyte retention and ionization in LC-MS, especially for challenging amino compounds. The article dives into reagent selection, method optimization, and real-world troubleshooting – tools I wish I’d had starting out.”

This work was supported by the Estonian Research Council grant PUT1589, and by the Estonian Ministry of Education and Research (TK210). The research was conducted using the Estonian Center of Analytical Chemistry, funded by the Estonian Research Council (TT4).

Graphical abstract for the tutorial review

Measurement uncertainty online course 12th run has successfully finished!

On May 14, 2025, the on-line course (MOOC) Estimation of measurement uncertainty in chemical analysis offered by the University of Tartu finished successfully. Eventually, altogether 1061 people registered from 100 countries. 525 participants actually started the course (i.e. tried at least one graded test at least once). The overall completion rate was 29%. The participation rate was 49% this year. The completion rate of the participants who started the studies was 59%, with 307 successfully finished participants. This result is quite stable during the 12 runs. This result can be considered good for a MOOC, especially for one that has quite difficult calculation exercises, which need to be done correctly with a limited number of attempts to complete the course. All statistics during the 12 years can be found in the table below.

The participants were very active and asked lots of questions. The questions were often very much to the point and addressed things that are really important to analysts in their everyday work. The course has several forums (general and by topic), and during the course period, the overall number of forum posts was above 400 (!) (overall number of posts, both from participants and from teachers) and the forums are still active and posts are still coming in. We want to thank all participants for helping to make this course a success! We plan to repeat this course again in Spring 2026!

Paleoproteomics course by visiting Professor Matthew Collins

Prof. Collins (left) with the students demonstrating the working principles of mass spectrometry

From the 17th to the 21st of March, the Archemy group welcomed Professor Matthew Collins, a Professor of Paleoproteomics at University of Cambridge and the University of Copenhagen, at University of Tartu for a week-long paleoproteomics course.

The course, attended by students and researchers from University of Tartu and the Collège de France, covered the fundamentals, methods, and applications of ancient proteomic studies using both MALDI-TOF mass spectrometry and LC-MS/MS.

Since the attendees’ backgrounds varied from archaeologists to chemists and geneticists, the course began with a review of the fundamentals of organic chemistry. Masterfully, Prof. Collins continued with an introduction to mass spectrometry and a method called ZooMS – zooarchaeology by mass spectrometry, which is based on detecting marker peptides to determine animal taxonomy.

The course continued with an intensive introduction to analyzing the paleoproteome using LC-MS/MS and the opportunities it provides in analyzing ancient ways of life, for example, determining the species used for dairy production. However, the shortcomings of the methods were also discussed. In archaeological material, the most prevailing issues tend to be contamination with modern and more abundant proteins, as well as the deamination of amino acids due to their advanced age. Despite the difficulties in analyzing ancient proteomes, the debates on the final day still concluded that the methods are highly applicable in archaeological studies.

Prof. Matthew Collins led the intensive course within the project PaleoMIX: Nurturing Heritage Science with Novel Bioarchaeological Methods in the Eastern Baltics, PI Mari Tõrv (UT). Project partners include the University of Copenhagen, the University of Burgos, and the University of York.

Read more about paleoproteomics and its applications in an interview with Prof. Collins (in Estonian).

Unified and comparable quantification of catalytic activity of Brønsted acids is now possible!

Our group’s journey into catalytic studies began years ago. In the first period our main activity was measuring the pKa values of Brønsted acids catalysts and relating them with catalytic activity. However, it was always problematic that the catalytic activity was quantified by different authors in very different ways: different reactions, different substrates of the same reaction, different ways to express activity (rate constant, yield), different solvents, different concentrations, different temperatures… All this diversity makes comparing catalytic activity difficult to impossible.

So, we set forth to find a model reaction, define conditions and a unified quantitative parameter for expressing acatlytic activity of various Brønsted acid catalysts.

This endeavour has now reached its first result: PhD student gleb Maksimov from our group discovered that the transfer hydrogenation reaction with substituted quinoline has the suitable characteristics for this work and utilizing the Kimball-Collins theory modelling approach applied to rate constante (measured by NMR), a catalytic activity parameter was defined that enables unified and comparable quantification of the catalytic activity of Brønsted acids! The proof of principle is now published: Molecular Catalysis 2025, 573, 114846. Towards quantifying catalytic activity of homogeneous Brønsted acid catalysts.

Congratulatuons, Gleb!

However, this work is far from complete. Gleb together with new students will continue to improving te methodolog and widening the applicability of the approach so that many more results and with higher quantitative accuracy would be possible in the future. We are excited about the potential advancements and look forward to sharing more updates as the research progresses.

(This research was supported by grant PRG690 from the Estonian Research Council)

Integrating omics – NPLinker workshop in Wageningen

They say it takes a village to raise a child—and in science, it takes a community to push boundaries and do great science. In the multi-omics field, the best discoveries emerge from collaboration among chemists, microbiologists, bioinformaticians, computer scientists, and many others.

The NPLinker community in Wageningen, Netherlands, is dedicated to bridging the gap between genomics and metabolomics while also connecting researchers analyzing these complex datasets.

This week Pilleriin Peets had the fantastic opportunity to once again participate in their five-day intensive hands-on workshop, which covered key tools and applications, including BiG-SCAPE, MZmine, GNPS2, NPLinker, and PairedOmics.

A highlight of the week was the Symposium on March 26, celebrating 10 years of genomics mining and 5 years of metabolomics mining at Wageningen University & Research. Genomics mining research in Wageningen is led by Marnix Medema, whose developments include antiSMASH and MIBiG. Metabolomics topics were covered by Justin J.J. van der Hooft, whose contributions to the field include PairedOmics platform, as well as MS2Query.

The symposium’s keynote was delivered by Pieter Dorrestein, one of the most influential scientists in metabolomics, with over 400 publications and 75,000 citations. His work in computational metabolomics includes the Global Natural Products Social Molecular Networking (GNPS) platform, which enables researchers to find spectral connections within their samples and annotate compounds using publicly available spectra. During his talk, he highlighted his bile acid research and emphasized the critical role of open-access data in advancing the field.

Knowledge from this week will be brought back to Tartu and Pilleriin is eager to integrate GNPS2 into her workflow to enhance compound annotation in her non-targeted mass spectrometry datasets.