The Chair of Analytical Chemistry at University of Tartu

Estimating measurement uncertainty in chemical measurements: difficulties and misconceptions

At the recent 10th Conference on Chemometrics, Metrology and Artificial Intelligence in Analytics conference in Poznań, Ivo Leito presented a keynote talk titled Estimating measurement uncertainty in chemical measurements: difficulties and misconceptions.

The presentation outlined three important misconceptions in estimation of measurement uncertainty in chemical measurements: (1) Uncertainty is primarily determined by the accuracy of the instrument; (2) Uncertainty is quantitatively expressed by (dis)agreement between results of repeated measurements and (3) „Simple“ measurements are simple.

All three misconceptions were debunked during the talk on the basis of the research of our group from the recent years: (1) In chemistry, uncertainty mostly comes from the object, not from the instrument; (2) In chemistry, uncertainty usually comes mainlyfrom systematic effects,not from (within-day) random effects and (3) In chemistry, even for „simple“ measurement,adequate modeling and evaluation of individual uncertainty components is usually challenging.

The presentation made use of the recent work of our group: S. Pawade et al “A quantitative approach to determine water and moisture content of different types of lignin using attenuated total reflectance Fourier transform infrared spectroscopy combined with partial least squares regression” Biofuels, Bioprod. Bioref. 2026; L. Sooväli et al “Uncertainty sources in UV-Vis spectrophotometric measurement” Accred. Qual. Assur. 2006, 11, 246-255; “Critical compilation of acid pK_a values in polar aprotic solvents” Pure and Applied Chemistry, 2025, 97, 973-998; I. Helm et al “Comparative validation of amperometric and optical analyzers of dissolved oxygen: a case study” Environ. Monit. Assess. 2018, 190.

The presentation presented a pragmatic solution to measurement uncertainty evaluation of chemical measurement results: the approach based on validation and quality control data (also known as the single-lab validation approach).

The presentation was warmly received by the participants, receiving a number of quations and coffee break discussions!

(This research presented in the talk has been supported by the IUPAC project 2015-020-2-500, MetPart 23RPT03 GrainMet, Estonian Ministry of Education and Research (TK210), Estonian Research Council grants IUT20-14, PRG690 and PRG1557, Estonian Center of Analytical Chemistry, www.akki.ee)

New article on ancient dietary analysis by Archemy Group

The Archemy group is happy to share the latest article published in the Journal of Archaeological Method and Theory – Food Equality: Multiproxy Biomolecular Dietary Analysis Shows Unstratified Foodways Among Protohistoric E Baltic Communities.

The paper is crucial milestone for the group serving as an excellent example of collaborative analytical work combining all the multiple expertises of the Archemy. The results do not only challenge our previous understanding of Conversion period social dietary practices in Estonia, but will serve as a key-reference for future multi-proxy and multi-method dietary analysis. The main findings include:

*There was no major dietary difference between men, women and children in the 12th-13th century AD Pada community: all had equal access to food sources!

*Meat-based foods were preferred in burial ritual contexts, whilst plant-based foods formed majority in daily food consumption.

*No single proxy approach or method can reveal the full spectrum of ancient dietary practices.

Many thanks to all the amazing collaborators who contributed to this work!

New publication: determining water content in lignin using ATR-FTIR

Shrikant performing the FTIR measurements

We are delighted to share that our latest article titled “A quantitative approach to determine water and moisture content of different types of lignin using attenuated total reflectance Fourier transform infrared spectroscopy combined with partial least squares regression” has been published in the journal of Biofuels, Bioproducts and Biorefining (Volume 20, 2026). The article was authored by Shrikant Shivaji Pawade, together with Dr Martin Vilbaste, Andres Siiman, Dr Lauri Toom, Associate Professor Koit Herodes, and Professor Ivo Leito. The article is Open Access and available online; click here to access it.

The study presents a quantitative methodology for determining water and moisture content in diverse lignin types using ATR-FTIR spectroscopy combined with partial least squares regression, with vapourisation–coulometric Karl Fischer titration (vap-C-KFT) and gravimetric methods used as reference techniques. In addition, the work introduces a sigmoid curve approach to temperature optimisation for vap-C-KFT and evaluates sampling and modelling uncertainties, thereby providing practical insights for reliable lignin characterisation. The robustness of the method was assessed by validation against vap-C-KFT, oven drying (7 h and 48 h), and freeze-drying, utilising diverse lignin types (Kraft, Dealkaline, and Lignova Fibenol) and achieving RMSEP values ranging from 0.33 to 1%.

The results demonstrate that ATR-FTIR combined with chemometrics modelling can provide a rapid, simple, and cost-effective alternative to conventional methods, while maintaining good accuracy across diverse lignin types.

Measurement Uncertainty MOOC: Registration is now open!

The 2026 edition of the web course (MOOC) Estimation of Measurement Uncertainty in Chemical Analysis will run from March 24 to May 6, 2026. Registration is now open!

The full course material (as well as the registration link) is accessible from the web page. The course materials include videos, schemes, calculation files, and numerous self-tests (among them also full-fledged measurement uncertainty calculation exercises) and examples. Almost all areas of analytical chemistry are addressed, ranging from simple volumetric operations and titrations to sophisticated instrumental analysis, such as determining pesticide residues by LC-MS. Efforts are made in the course to address also such uncertainty sources encountered in chemical analysis that are difficult to quantify, e.g. uncertainty due to possible interference effects (incomplete selectivity), analyte losses, etc.

In order to pass the course, the registered participants have to take six graded tests and get a higher than 50% score in every graded test. These tests are available to registered participants via the Moodle e-learning platform.

Participants who successfully pass the course will get a certificate from the University of Tartu. A digital certificate of completion is free of charge. A certificate of completion on paper can be requested for a fee of 62 euros.

You are welcome to distribute this message to potentially interested people!

A new article about a developed laser ablation-based mass spectrometric system for the analysis of cultural heritage materials has now been published!

The Cultural Heritage research group, as part of this year-end PRG1198 research project, has published an open-access article titled “Laser ablation APCI-HRMS method for the analysis of cultural heritage materials” by Anu Teearu, Martin Leissoo, Rynno Lohmus, Alexey Treshchalov, Tõiv Haljasorg, Victor Augusto Xavier da Silveira, Hilkka Hiiop, and Signe Vahur in the Journal of the American Society for Mass Spectrometry. The article is available here.

This research article highlights a novel 355 nm optical fibre-coupled laser ablation (LA)-APCI-FT-ICR-MS system, developed for direct, controllable, rapid, and accurate analysis of organic materials from the solid surface of an artefact under ambient conditions with minimal surface damage and without the need for sample removal or sample preparation for the analysis. In this study, the effectiveness and capabilities of the developed LA-APCI-HRMS system for analysing five aged mock-up materials (copper resinate, Prussian blue oil and egg tempera paints, lead white oil paint and matte dammar varnish) and the blackish-brown material from an ointment jar from a 16th-century shipwreck were investigated. The results can be read in the article.

The PRG1198 project team has done excellent work over the past five years, culminating in a working laser-based HRMS system. The same team will begin next year with a new project, and we will continue to keep you updated on all new developments.

In the photo, the main members of the PRG team: team leader Dr Signe Vahur (in the centre), from left Dr Aleksei Treshchalov, Prof. Hilkka Hiiop, Dr Anu Teearu-Ojakäär, Dr Rünno Lõhmus and specialist Martin Leissoo.

LC-MS Method Validation web course: 999 participants from 95 countries!

On Tuesday, December 16, 2025 the web course LC-MS Method Validation was launched for the tenth time as a MOOC (Massive Online Open Course). There are 999 registered participants from 95 countries, ranging from Canada to New Zealand and from Peru to Thailand. The image above shows the countries where the participants come from.

This is a practice-oriented on-line course on validation of analytical methods, specifically using LC-MS as the technique. The course introduces the main concepts and mathematical apparatus of validation, covers the most important method performance parameters and ways of estimating them. The LC-MS validation course is delivered by a team of 7 teachers, each with their own specific area of competence. This way it is expected to offer the best possible knowledge in all the different subtopics of analytical method validation.

The full set of course materials is accessible from the web page https://sisu.ut.ee/lcms_method_validation/. The course materials include videos, schemes, calculation files and numerous self-tests (among them also full-fledged calculation exercises). In order to pass the course, the registered participants have to take all tests and get higher than 50% score from each of them. These tests are available to registered participants via the Moodle e-learning platform. Participants who successfully pass the course will get a certificate from the University of Tartu.

Our LC-MS validation activities at the IUPAC-DSM LC-MS validation workshop

Riin Rebane, Asko Laaniste and Ivo Leito participated on 10-11.12.2025 in the Joint IUPAC-DSM Workshop on LC-MS method validation and performance, organised jointly by the IUPAC’s Division of Analytical Chemistry and the Mass spectrometry division (DSM) of the Italian Chemical Society.

Riin presented the opening keynote of the event titled “Principles of method validation”. Her presentation reframed LC-MS method validation as a risk-management process rather than a checklist of validation characteristics. By zooming out to the method’s intended purpose, each validation characteristic is linked to the specific risks it is designed to control. This view allows to build evidence that the method performs reliably under real-world conditions and is truly fit for purpose and produces results with known confidence.

Ivo’s talk “What are the issues encountered in the real world? Lessons learned form an online validation course” presented an analysis of the main issues brought up by the participants of the nine editions of an online LC-MS method validation course (https://sisu.ut.ee/lcms_method_validation/). The analysis of 2640 course forum posts and 336 participant feedback submissions revealed that practitioners struggle a lot with calculations and spreadsheet software, which diverts effort from real “analytical hemistry” issues.

Asko’s session “ValChrom open-access online validation software” was a workshop in the true sense of the word: a hands-on session on the online validation software ValChrom developed at UT. Participants had instant access to the software freely available in web and demo materials. Asko walked them through the whole process of ValChrom from start to finish, from defining analytes to customizing experimental plan with AI and finishing with automatically generated DOCX file with the whole validation data in it. ValChrom’s Design of Experiements (DoE) capabilities were also covered and it was nice to see that throughout the two days a big number of presentations also involved DoE one way or another, indicating a rising need for such tools.

All in all, the contributions of our team were highly appreciated, indicated by numerous questions, both during sessions and (especially) during coffee breaks.

Tenth run of the On-line LC-MS Method Validation Course: already 536 registered people!

The tenth edition of the course on LC-MS Method Validation already has 536 registered participants! Don’t miss your chance to join – spots are filling up fast. Register now (here) and start learning! The course will be offered as a Massive Open On-line Course (MOOC) from Dec 16, 2025 to Feb 27, 2026.

This is a practice-oriented online course on validation of analytical methods, specifically using liquid chromatography-mass spectrometry (LC-MS) as the technique, mostly (but not limited to) using the electrospray (ESI) ion source. The course will also be of interest to chromatography practitioners using other detector types. The course introduces the main concepts and mathematical apparatus of validation, covers the most important method performance parameters and ways of estimating them. More information about the course can be found on the Course introduction page.

Participation in the course is free of charge. Receiving a digital certificate (in the case of successful completion) is also free of charge. A printed certificate (to be sent by post) is available for a fee of 61 EUR. Registration is possible until the start of the course. The course material is available from the above address all the time and can be used via the web by anyone who wishes to improve their knowledge and skills in analytical method validation (especially when using LC-ESI-MS).

You are welcome to distribute this message to potentially interested people!

On-line LC-MS Method Validation Course 2025-2026: Registration is open!

The tenth (!) edition of the online course LC-MS Method Validation is open for registration (registration link is here)! The course will be offered as a Massive Open On-line Course (MOOC) during December 16, 2025 – February 27, 2026.

This is a practice-oriented on-line course on validation of analytical methods, specifically using liquid chromatography-mass spectrometry (LC-MS) as technique, mostly (but not limited to) using the electrospray (ESI) ion source. The scope of the course is sufficiently broad, so that it will be useful also to chromatography practitioners using other detector types. The course introduces the main concepts and mathematical apparatus of validation, covers the most important method performance parameters and ways of estimating them. More information about the course can be found in the Course introduction page.

Participation in the course is free of charge. Receiving digital certificate (in the case of successful completion) is also free of charge. Printed certificate (to be sent by post) is available for a fee of 61 EUR. Registration is possible until the start of the course. The course materials are available from the above address all the time and can be used via web by anyone who wishes to improve the knowledge and skills in analytical method validation (especially when using LC-ESI-MS).

This year’s recipients of honorary decorations have been announced

Ivo Leito and Koit Herodes were awarded honorary decorations by the University of Tartu.
Professor Ivo Leito received the University of Tartu Grand Medal, and Associate Professor Koit Herodes received the University of Tartu Badge of Distinction.

Ivo, our Professor of Analytical Chemistry, has been recognised with the university’s highest internal honour for services of particular value. The Grand Medal highlights Ivo’s internationally renowned scholarship that blends high-level fundamental research with metrological precision and innovative teaching. His excellent leadership and mentorship have shaped generations of chemists and strengthened the standing of analytical chemistry at the University of Tartu and beyond.

Koit, our Associate Professor of Analytical Chemistry, has been awarded the University of Tartu Badge of Distinction in acknowledgement of his dedicated service to the University. Koit’s contributions to analytical chemistry spanning from research to teaching have had a strong positive impact on our group’s scientific excellence and student experience.

The decisions were made by the University of Tartu senate on October 31. The University will present this year’s honorary decorations at a ceremony on 21 November at 16:00 in the University of Tartu assembly hall. More information and the other recipients can be found here.

Please join us in congratulating Ivo and Koit on these well-deserved recognitions!