Measurement uncertainty online course 2020: highest ever completion rate: 55%!

On May 12, 2020 the on-line course (MOOC) Estimation of measurement uncertainty in chemical analysis offered by University of Tartu finished successfully.
Eventually altogether 843 people registered (270 in 2014, 489 in 2015, 757 in 2016, 363 in 2017, 521 in 2018, 590 in 2019) from 95 countries (a number of participants joined after the start of the course). 600 participants actually started the course (i.e. tried at least one graded test at least once) and out of them 464 successfully completed the course (141 in 2014, 169 in 2015, 308 in 2016, 148 in 2017, 358 in 2018, 238 in 2019). The overall completion rate was 55% (52% in 2014, 34% in 2015, 40% in 2016, 41% in 2017, 42% in 2018, 40% in 2019). The completion rate of participants who started the studies was 77% (67% in 2014, 60% in 2015, 67% in 2016, 68% in 2017, 61% in 2018, 62% in 2019). The completion rate this year is the best we have seen and can be considered excellent for a MOOC, especially one that has quite difficult calculation exercises, which need to be done correctly for completing the course.

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 close to 600 (!) (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 of this MOOC a great experience also for us, the teachers. The discussion threads gave a lot of added value to the course and some of them triggered making important modifications to the course materials, even during the course.

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

We plan to repeat this course again in Spring 2021.


Measurement Uncertainty online course, Mar 24 – May 5, 2020: Registration is open!

The 2020 edition of the web course (MOOC) Estimation of Measurement Uncertainty in Chemical Analysis will be running during Mar 24 – May 5, 2020. Registration is 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 titrations to sophisticated instrumental analysis, such as determining pesticide residues by LC-MS.

In order to pass the course, the registered participants have to take six graded tests and get 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 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 60 euros.

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


Highly Acidic Conjugate‐Base‐Stabilized Enantioselective Carboxylic Acid Catalysts

We recently had the pleasure of collaborating with the group of Daniel Seidel (University of Florida) in the field of enantioselective acidic catalysis. Prof. Seidel and his co-workers have developed Highly Acidic Conjugate‐Base‐Stabilized Enantioselective Carboxylic Acid Catalysts that are able to catalyze oxa‐Pictet–Spengler Reactions with Ketals. Our task in this endeavor was determining the acidity of the catalysts involved and elucidating the effect of the different elements of its substitution scheme on acidity. The main outcome is summarized in the scheme on the left. As can be seen, the most acidifying element is the substituted thiourea moiety, leading to one of the catalysts – the rightmost molecule. The findings strongly suggest that a key to the high acidity is the intramolecular hydrogen bond stabilizing the anion of the acid catalyst. These same substituents are also instrumental in the enantioselective catalytic ability of these catalysts.

This work has been published in Angew. Chem. Int. Edit. 2019.

LC-MS Method Validation web course: 511 participants from 77 countries!

On Tuesday, November 26, 2019 the web course LC-MS Method Validation was launched by our group for the fourth time as a MOOC (Massive Online Open Course). There are 511 registered participants (the largest number ever in this course) from 77 countries, ranging from Guatemala to Azerbaijan and from Finland to Sudan. Image on the left 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 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 8 teachers form our group, 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 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.


Minireview on pKa values of bases in non-aqueous solvents

In a recent minireview, published in Eur. J. Org. Chem. an important part of our group’s acid-base chemistry research has been summarized: the pKa values of bases (pKaH values) determined over the years in acetonitrile have now been rigorously united into a single scale, whereby all the involved ΔpKa values have been considered for deriving the absolute pKaH values of the bases involved. Altogether 279 basic compounds are included in the scale from all major groups of organic bases (amines, pyridines, imidazoles, anilines, amidines, guanidines, phosphazenes, etc) and are linked with altogether 682 ΔpKa measurements. The full scale can be downloaded by clicking on the picture on the left. The minireview also presents possibilities to predict the pKa values of bases in other media – namely water, DMSO and THF – on the basis of MeCN pKaH values. It is expected that this minireview will be a useful tool for future researchers who need pKa values of bases in nonaqueous solvents for planning their studies or for interpreting research results.  

Our acid-base research at 19th European Symposium on Fluorine Chemistry 2019

On 26.08.19 at 19th European Symposium on Fluorine Chemistry 2019 Ivo Leito gave a talk Acidities of molecules and media: the united pKa-pHabs scale in 1,2-dichloroethane.

For the first time in a low-polarity solvent, the scale has a dual nature, being both a pKa scale of the involved acids (i.e. describing acidity of molecules) and at the same time a pH scale, describing the acidity of the solutions (media).

The scale spans 28 orders of magnitude (pH or pKa units) and is composed of 87 acids of diverse nature. The scale is linked to the unified acidity (pHabs) scale and expressed in values, which makes the acidities of the solutions directly comparable to the conventional aqueous pH scale. This in turn makes the scale a useful tool in future studies of acid-driven processes (reaction mechanisms, catalysis, strong oxidants, etc) in low-polarity media.

This work has been published in: Chem. Sci., 2017, 8, 6964-6973. A unified view to Brønsted acidity scales: do we need solvated protons?.

It is part of a larger endeavor – to promote a wider usage the unified pH scale by the research and technology communities, which is currently in progress via the UnipHied. The project is funded from the EMPIR programme (project 17FUN09) co-financed by the Participating States and from the European Union’s Horizon 2020 research and innovation programme.  

Eurachem 2019 workshop successfully finished!

Our group was the main organiser of the Eurachem 2019 Scientific workshop Validation of targeted and non-targeted methods of analysis, which took place in Dorpat Conference Centre in Tartu during May 20-21, 2019. This workshop also marks the 30th anniversary of Eurachem.

Approximately 160 people attended the workshop, which is the largest number of participants in the history of Eurachem workshops! The participants were from 42 countries of the member countries in Eurachem as well as Asia, North America, South America and Middle East. The farthest participants were from Fiji, the Philippines, Uruguay and Brazil.

The workshop was held with 13 oral presentations from established researchers, young scientists as well as industries. Together with 22 posters all presentations reflected the current and potential future developments related to methods validation. The workshop addressed the current status of analytical method validation in general and specifically validation of the non-targeted methods (i.e. ones where the analyte is not defined beforehand). With the speaker permissions, all presentations will shortly be available at the Eurachem website. In addition to presentations, each day a Working Group session was organised with 3 topics in parallel (Image on the left: Welcome by Dr Marina Patriarca, the Eurachem chair).

Non-targeted methods are an especially noteworthy part of the programme, because their validation involves specific issues and their validation is significantly less developed than validation of targeted methods (i.e. the “normal” analytical methods, where the analyte is known beforehand). At the same time non-targeted methods are becoming increasingly important in environmental protection, food safety, different omics areas, etc. (Image on the right: Prof. Jon Benskin from Stockholm University presenting an introduction to non-targeted analysis)

All sessions raised new issues and challenges, especially related to non-target method validation. The workshop clearly was also very inspirational for Eurachem from the point of view of preparing new guideline materials – especially the topics related to non-targeted analysis are still essentially not covered by official guidance documents.

Some example topics of the workshop: Validation of targeted methods: where are we? Validation of non-targeted methods – differences from targeted methods. Detection of a multitude of (unknown) components in complex samples: criteria for identification. Managing the huge amounts of complex data from non-targeted methods. Recent instrumental developments. Software tools for validation. (Image on the left: Dr. Koit Herodes presenting the ValChrom validation software)

The workshop certaily had a significant educational value and we are pleased by the large number of student participants: altogether close to 50! The international master’s programmes Excellence in Analytical Chemistry and Applied Measurement Science were both heavily represented: the majority of students of those programmes participated in the workshop (Image on the left: EACH and AMS students at the workshop).

The workshop was jointly organized by Eurachem and ECAC (University of Tartu, Tallinn University of Technology and the Estonian Environmental Research Centre).


Fluorescence spectroscopy course by EACH visiting scholar Todd Pagano

During Apr 22 to May 4 we had the pleasure to host visiting scholar, prof. Todd Pagano from the Rochester Institute of Technology (RIT), USA. He conducted, for the second time, a two week-intensive course Principles and applications of fluorescence spectroscopy.

In this course, students reviewed the principles of fluorescence spectroscopy, were introduced to the impact of photophysical phenomena on fluorescence data, and discussed new directions of fluorescence in analytical chemistry. Techniques in multidimensional fluorescence spectroscopy with chemometric analysis were highlighted, especially in the context of novel applications in environmental and related fields. The course consisted of lectures, seminars, tutorial sessions and two lab practicals. The latter were specifically set up for this course by prof. Pagano and were very much appreciated by students.

The first practical was about discovering the fundamental concepts of fluorescence (excitation and emission spectra, Stokes shift, Vavilov’s rule, fluorescence lifetime, etc). The second practical was about analysis of caffeine in beverages using salicylic acid as a fluorescent chemosensor. This analysis utilizes the ability of caffeine to quench the fluorescence of salicylic acid and introduces students to the fluorescence quenching, Stern-Volmer equation and inner filter effects.

Altogether 30 students (out of them 14 EACH students) participated in the course and their feedback was overwhelmingly positive.


Prof. Pagano is a passionate educator. He was the initiator of the Laboratory Science Technology program at Rochester Institute of Technology’s National Technical Institute for the Deaf, which is a unique science programme, specifically designed for deaf students. He was named “2012 U.S. Professor of the Year” by the Council for Advancement and Support of Education and the Carnegie Foundation for the Advancement of Teaching.


(Images: top left, group photo of prof. Pagano with course participants; right: prof. Pagano with students in lab)


ESI outcompetes other ion sources in LC-MS trace analysis

Choosing the best possible ion source is a very important step in liquid chromatography-mass spectrometry (LC/MS) method development. In a recent paper,  ESI outcompetes other ion sources in LC-MS trace analysis Anal. Bioanal. Chem. 2019 Asko Laaniste from the UT Analytical chemistry group carried out a large scale survey of different LC/MS ion sources (and their different working modes) as applied to pesticide analysis. He compared electrospray ionisation (ESI) source, thermally focused/heated electrospray (HESI), atmospheric pressure photoionisation (APPI) source with and without dopant, and multimode source in ESI mode, atmospheric pressure chemical ionisation (APCI) mode, and combined mode using both ESI and APCI, i.e. altogether seven different ionisation modes for the analysis of 40 pesticides (see list below).

The lowest limits of detection (LoDs) were obtained by ESI and HESI. The widest linear ranges were observed with the conventional ESI source without heated nebulizer gas. ESI source was significantly less affected by matrix effect than the HESI source. APPI ranked second (after ESI) by not being influenced by matrix effect; therefore, it would be a good alternative to ESI if low LoDs are not required.

It was somewhat unexpected that ESI outperformed HESI. This may be caused by the instability of the additional heated gas (sheath gas) in HESI that is used in addition to the nebulising gas.

In conclusion, as a broad generalisation, Asko’s results show that although several new ion sources have been introduced during the last decade, the conventional ESI performs at least equally to these new ion sources in the case of polar to medium polarity pesticides. ESI with thermal focusing (HESI) performed more or less equally with ESI in terms of LoD. At the same time, HESI had significantly poorer intermediate precision of matrix effect values for most compounds. Thus, for trace analysis, ESI is still the ion source of choice.

(Full list of pesticides: pymetrozine, thiamethoxam, methiocarb-sulfoxide, chloridazon, imidacloprid, acetamiprid, methiocarb-sulfone, thiacloprid, imazalil, thiophanate-methyl, metribuzin, pyrimethanil, fenpropimorph, spiroxamine, propoxur, triasulfuron, bupirimate, paclobutrazol, methiocarb, azoxystrobin, epoxiconazole, myclobutanil, fenhexamid, fluquinconazole, flusilazole, mepanipyrim, bitertanol, propiconazole, triazophos, methoxychlor, ditalimfos, tebufenozide, benalaxyl, pyrazophos, buprofezin, indoxocarb, trifloxustrobin, quinoxyfen, pirimiphos-ethyl, hexythiazox)


(Image top left: Asko Laaniste preparing solutions; Image right: Comparison of accuracy of LC-MS analysis using different ion sources)


How to make maximum use of the available pKa data in non-aqueous solvents?

On 11.04.2019 Ivo Leito gives a presentation titled “How to make maximum use of the available pKa data in non-aqueous solvents?” at 26th Croatian Meeting of Chemists and Chemical Engineers (26HSKIKI), in Šibenik (Croatia). The presentation discusses the principles of acid-base behaviour in solvents and on how to estimate the pKa values of compounds in solvents where direct experimental data are not available.