Shrikant’s PhD defence – from lignin chemistry to NMR and from uncertainty estimation to water measurement with KF titration and FTIR!

Shrikant discussing with the opponents

On the 9th of June 2026, Shrikant Shivaji Pawade successfully defended his dissertation Metrological aspects of sampling and water/moisture determination on the example of lignin. As the thesis encompassed a wide range of topics – from lignin chemistry to NMR and from uncertainty estimation to water and moisture content measurement with ATR-FTIR – there were two opponents invited to examine the PhD candidate: Dr. Stephanie Bell (NPL, UK) and Prof. Riina Aav (TalTech, Estonia).

Development of a rapid and non-destructive method for water and moisture content in lignin using ATR-FTIR with PLS calibration

The defence was intensive and entertaining and eventually Shrikant managed to convince the opponents, the defence committee and the listeners that he was on top of the topics that his dissertation embraces. Please accept our warm congratulations, Shrikant!

The dissertation’s main contribution was development of a rapid and non-destructive method for determining water and moisture content in lignin using ATR-FTIR with PLS calibration.

Modelling of temperature-dependent water release to identify suitable evaporation temperatures for oven cKF titration

The method requires a small amount of sample amount and minimal sample preparation. For developing the method, Shrikant prepared a range of calibration and validation samples from lignins of four different origins (two different types of Kraft lignins, Lignova lignin and dealkaline lignin). Water content was determined using vapour-phase coulometric Karl Fischer titration (i.e. oven-cKF titration), supported by modelling of temperature-dependent water release to identify suitable evaporation temperatures. Moisture content was determined gravimetrically using oven drying (at 105 °C, 7 h or 48 h) and lyophilisation (freeze-drying).

Water and moisture content is an important quality characteristic of not only lignin but essentially any natural feedstock. So, it is expected that the results of Shrikant’s thesis will find use in applied bioproducts research, as well as in industrial biorefineries.

Equilibrium Brønsted acidity measurements in 1,2-difluorobenzene

Table 1

We are pleased to share our latest open-access article titled “Acidity scale in 1,2-difluorobenzene” by John Paulo Samin, Helerin Roomet, Märt Lõkov, Sofja Tshepelevitsh, Jaan Saame, Agnes Heering, and Ivo Leito, published in ACS Omega (DOI: 10.1021/acsomega.6c02089).

In this work, we established equilibrium Brønsted acidity measurements in 1,2-difluorobenzene (1,2-DFB) in terms of pKa values measured by UV-vis spectrophotometry and unified pH (pHabs) values measured by differential potentiometry.

The pKa scale in 1,2-DFB spans 15 orders of magnitude. The pKa values were determined for 137 acids, 33 of which were directly measured (see Table 1). The remaining values were estimated using correlation equations relating pKa values in other solvents (acetonitrile and 1,2-dichloroethane) to those in 1,2-DFB. The pKa scale was anchored to the computational pKa values of 9 acid compounds.

Furthermore, an experimental unified pH scale spanning more than 10 orders of magnitude was established. The scale was aligned to the aqueous pH scale, assigning pHabsH2O values to the buffer solutions of 22 acids ranging from −0.6 to 10.0 (see Table 2). The potentiometrically measured pHabsH2O values showed good agreement with the values independently calculated from experimental pKa values anchored to computational reference values, demonstrating the solid foundation of the underlying theory.

These results open the possibilities for quantitatively describing and measuring acid−base processes in 1,2-DFB, including potentiometric and UV−vis spectrophotometric pHabsH2O measurement.

(This research was supported by grant PRG2557 from the Estonian Research Council and TK210 from the Estonian Ministry of Education and Research.)

Table 2

Visting lecturers – Dr Burcu Binici and Dr Alons Lends

Dr Burcu Binici giving a lecture on metrology

In April, our group hosted two experts who gave lectures on their topics.

First, on April 14-15, Dr Burcu Binici, a specialist at TUBITAK UME (the National Metrology Institute of Türkiye), presented materials on CRMs in the chemistry field to students in the Metrology in Chemistry course. The listeners had the opportunity to broaden their understanding of CRM, RM production, and the requirements for that.

Then, on the weekend of April 17–18, Dr Alons Lends led an intensive NMR course. He is currently working at the Latvian Institute of Organic Synthesis and has extensive experience in various NMR applications. During his course, students and the members of the Analytical Chemistry group learned more about NMR in biomolecular studies and materials science.

 

Dr Alons Lends giving a lecture on NMR

Ahmed, a student of the EACH (Excellence in Analytical CHemistry) Master’s program, said about the lectures: “This is what makes EACH special: learning directly from experts. One of the best things about the EACH program is that it brings experts to teach specific parts of your curriculum or to give you a deep dive into fields you already know. That’s what makes you feel very comfortable, as you can get very good answers to your questions from experts.”

9700 Quality-evaluated pKa values of more than 5000 acids in 7 dipolar aprotic solvents!

14.04.2026: The Zenodo data collection (Image on the right)) recently published as IUPAC technical report Acid dissociation constants in selected dipolar non-hydrogen-bond-donor solvents. Pure and Applied Chemistry. 2025, 97, 973, https://doi.org/10.1515/pac-2024-0276 has been updated for the first time by new pKa values so that its version 1.5.0 now contains more than 9700 quality-evaluated pKa values of more than 5000 acids in 7 dipolar aprotic solvents (DMSO, MeCN, DMF, pyridine, acetone, propylene carbonate and THF). The values have been collected from around 800 original works. The widest possible selection of compound classes is covered (Table below). The results of this large-scale pKa 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 pKa 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).

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 grants (PRG690, PRG2557) and by the Estonian Ministry of Education and Research (TK210).

Measurement Uncertainty online course: 797 participants from 96 countries!

On Tuesday, March 24, 2025 the web course Estimation of Measurement Uncertainty in Chemical Analysis was launched the twelfth time as a MOOC (Massive Online Open Course)!Altogether 797 participants from 96 countries are registered! In the map presented above, the yellow color marks the countries from where participants come. True, the map is coarse and some countries are small. Therefore, not all countries are visible. We are very happy that we have 4 participants also from Ukraine this year. Slava Ukraini!
Registration for this run is closed. But good news: if you did not manage to register this time, you are welcome to register for the 2027 edition of the course.

The full course material is accessible from the web page https://sisu.ut.ee/measurement/uncertainty. The course materials include videos, schemes, calculation files and numerous self-tests (among them also full-fledged measurement uncertainty calculation exercises). In order to pass the course, the registered participants have to pass six graded tests and get higher than 50% score from each of them. These tests are available to registered participants via the Moodle e-learning platform.

This course is run under the umbrella of the Estonian Center of Analytical chemistry (https://www.akki.ee/) and forms a part of the Excellence in Analytical Chemistry (https://www.analyticalchemistry.eu/) Erasmus Mundus master’s programme.

LC-MS Validation online course 10th run has finished!

On March 6, 2026 the on-line course (MOOC) LC-MS Method Validation offered by University of Tartu finished successfully.

Eventually, altogether 995 people registered from 95 countries. Roughly half of them, 486 participants, actually started the course (i.e. tried at least one graded test at least once), and out of them, 337 successfully completed the course. The overall completion rate was 34%. The completion rate of participants who started the studies was 69%. The completion rates of active participants (i.e. who started the course) seem to have stabilised at around 60% and have increased during the current run. In any case, there is some food for thought for us on how we could improve the participation rate…

At the same time, those participants who actually took part in the course 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). During the course period, the overall number of forum posts was around 200 (overall number of posts, both from participants and from teachers), and the forums are still active, and posts are still coming in.

This active participation made teaching this MOOC a great experience also for us, the teachers. The discussion threads gave a lot of added value to the course.

We want to thank all participants for helping to make this course a success!

We plan to repeat this course again in Autumn 2026.

The Cultural Heritage Research Group started with a new PRG project!

In January 2026, the cultural heritage research group – in collaboration with physicists, material scientists, conservators, and IT specialists – launched a challenging new five-year Personal Research Funding Team (PRG) project, led by Dr Signe Vahur. The main goal of the PRG3112 project is to develop a novel, portable, automated laser ablation sampling probe. This tool will enable minimally destructive stratigraphic and imaging analysis of artefacts directly on the object under ambient conditions. In the future, the probe could be coupled with various analytical devices (MS, Py-GC-MS, and FORS) and sampling containers.

We will keep you updated on the progress of this demanding and exciting project!

The research team remains largely the same as in our previous project.

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.

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 mainly from 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 pKa 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.