Eliise Tammekivi, Author at Chair of Analytical Chemistry

Solid-State Composite reference electrodes

Recently, a collaborative study on the Solid-State Composite reference electrodes was published in the journal of Membranes 2022, 12, 569. Slim Blidi, EACH alumnus and the first author of this publication, provides here a short overview of this novel research.

Potentiometric measurements using conventional electrodes do have some drawbacks when used. This is especially true for the conventional liquid-filled reference electrodes. They are non-robust in use and are maintenance-intensive due to the necessity of refilling the inner solution and keeping the liquid junction clog-free.

By eliminating the liquid component from the electrode structure, Solid-State Composite (SSC) reference electrodes are a viable alternative to conventional reference electrodes. Prepared by either injection molding or chemical polymerization, they are based on a silver/silver chloride reference element enclosed in a polymeric matrix (e.g. polyvinyl acetate) mixed with an inorganic salt (potassium chloride). The composite is the inorganic salt storage material while being in contact with the sample solution.

In this study, a set of the SSC reference electrodes was prepared and their performance was tested in different synthetic solutions to assess the possible influence of pH, solution composition, as well as the concentration and mobility of ions. Using potentiometry and electrochemical impedance spectroscopy methods over a period of several months, stability tests were also performed to evaluate the suitability of the studied SSC reference electrodes for continuous, prolonged, and intensive usage. Concentrations of K⁺, Na⁺, Ca²⁺, and Cl^– ions and pH values were measured in river water samples at different temperatures using the SSC reference electrodes.

better than commercial liquid-filled reference electrodes in terms of calibration range and actual measurements. It is safe to say that SSC reference electrodes represent the future of potentiometric measurements applied to environmental samples as they are cheap to manufacture and easy to maintain.

I am extremely grateful to my supervisors at Åbo Akademi: Dr. Kim Granholm, Dr. Zekra Moussavi, and Dr. Tomasz Sokalski for their valuable guidance and moral support during the experimental work as well as to the EACH programme for this life-changing experience.

Ester Oras awarded L’Oreal-UNESCO “For Women in Science” Young Talents award

Ester Oras, the PI of our Archemy research group, was awarded L’Oreal-UNESCO “For Women in Science” Young Talents Program Baltics (Estonia) with the support of the Estonian Academy of Sciences and the Estonian National Commission for UNESCO scholarship.

Ester and her team work in biomolecular archaeology and employ modern omics methods – lipidomics, proteomics, and genomics – to reveal ancient dietary practices and diseases. By analysing centuries and millennia old ceramic vessels and human remains with topnotch laboratory techniques, Ester aims to show how past foodways affected the health of ancient populations, and reveal how historically developed dietary practices influence our overall wellbeing in the past as well as today. Ester says herself: “I want to give colour and taste to the past and bring the history closer to us today.”

L’Oréal-UNESCO For Women in Science Young Talents Programme aims to support and encourage young women researchers who represent the future of science in STEM fields. The Baltic regional programme opened first in Latvia in 2004 and widened to Lithuania and Estonia in 2017, with altogether 10 Young Talents recognised from Estonia so far.

Congratulations from all of us to you, Ester!

Measurement uncertainty online course 9th run has successfully finished!

On May 13, 2022 the on-line course (MOOC) Estimation of measurement uncertainty in chemical analysis offered by University of Tartu finished successfully.

Eventually, altogether 851 people registered from 103 countries. 405 participants actually started the course (i.e. tried at least one graded test at least once). The overall completion rate was 28%. This, as well as the participating rate was the lowest (48%) we have seen. However, the completion rate of the participants who started the studies was 59% with 239 successfully finished participants. Although lower than we have previously see, this result can still be considered very good for a MOOC, especially for one that has quite difficult calculation exercises, which need to be done correctly with limited number of attempts for completing the course. All statistics during the 9 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 over 500 (!) (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 2023.

A new exciting collaboration with famous contemporary Estonian artist Kaido Ole!

From left: Dr Signe Vahur, artist Kaido Ole, and Dr Hilkka Hiiop

On the 15^th of April, Dr Signe Vahur, Dr Hilkka Hiiop, and their Bachelor student Selene Margaret Pruuden visited Estonian painting artist Kaido Ole.

Kaido Ole has been one of the most well-known and awarded contemporary Estonian painters since 1989 and a long-time teacher and professor at the Estonian Academy of Arts. Ole’s work has a unique point of view, and his paintings are characterised by humour, self-irony and a critical sense of the absurd. Kaido Ole likes to use bright colours and different painting materials (oil paints, acryl paints, alkyd paints, etc.). More about Kaido’s creations can be seen on his webpage.

Our cultural heritage workgroup investigates different traditional materials and now more and more also modern synthetical and polymeric materials. Kaido Ole supports our modern materials research topic with his know-how as an artist and kindly shares his painting materials. In the future, we can investigate these materials also with our laser-pen probe-MS.

This collaboration is very new, and we are very excited to pursue this research. Thank you, Kaido!

[Show slideshow]

Atmospheric aerosols – Master’s project of Nieves Flores March

This week, Nieves Maria Flores March successfully defended her Master’s thesis named the “Organic Constituents of Atmospheric Aerosols in a Hemi-boreal Forest” and was awarded the highest grade – “A”!

In this project (supervised by Prof. Heikki Junninen), Nieves studied the chemical composition of organic aerosols collected from an Estonian Hemi-boreal forest during winter, spring, and summer. This research is important because atmospheric aerosols play a significant role in climate change and human health. However, the impact of boreal forests is difficult to characterize because of the chemical diversity of aerosol samples.

To get a better understanding of the chemical composition, Nieves applied two analytical methods – gas chromatography – mass spectrometry (GC-MS) and nuclear magnetic resonance (NMR) to the forests samples. For data analysis, she used a molecular networking technique to tentatively identify the possible compounds. She concluded, that the developed set of methods has great potential to perform fast screening of the chemical composition of atmospheric aerosols.

The GC-MS and NMR analyses were performed in collaboration with our Chair of Analytical Chemistry and we are happy to say that this joint and fruitful project will also continue in the future.

Congratulations to you, Nieves!

Measurement Uncertainty online course: 843 participants from 103 countries!

On Tuesday, March 22, 2022 the web course Estimation of Measurement Uncertainty in Chemical Analysis was launched for the ninth time as a MOOC (Massive Online Open Course)!

Currently, 843 participants from 103 countries are registered – the largest number of countries the course has ever had! In the map presented on the left, 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 one participant also from Ukraine this year. Slava Ukraini!

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 measurements and chemical analysis related master programmes at UT: Applied Measurement Science (https://ams.ut.ee/) and Excellence in Analytical Chemistry (https://www.analyticalchemistry.eu/).

Quantifying acidity in heterogeneous systems: Biphasic pKa values

As a result of a recent development in our group, it is now, for the first time, possible to rigorously measure acidity of acids in biphasic systems (aqueous phase at equilibrium with a water-immiscible phase) by using biphasic pK_a values (pK_a^ow values). This work has now been published in Analytical Chemistry 2022, 94, 4059–4064.

In this work, the octanol-water biphasic pK_a^ow values have been determined for 35 acids of various structures and chemical properties (carboxylic acids, phenols, diphenylamines, imides, different CH acids) using UV-Vis and NMR (¹H, ¹³C, or ³¹P) spectrometry.

Biphasic pK_a values enable quantifying acid dissociation in biphasic systems in a more realistic and rigorous way than the conventional “mono-phasic” pK_a values. The latter completely ignores a large part of the picture – partitioning of the neutrals and the ions between the two phases and ion-pairing in the low-polarity phase. In contrast, pK_a^ow values account for these effects. The ratio of the acid and its conjugate base is measured in the 1-octanol phase, using UV-Vis and/or NMR spectrometric method. The activity of H⁺ is measured in the aqueous phase with a conventional pH-meter. The pK_a^ow values are obtained at different concentrations and extrapolated to zero concentration.

Biphasic systems are present in many biological and technological systems and processes: cell membranes, solvent extraction, phase-transfer catalysis, sensor membranes, etc. In all such systems, acid-base properties of the participating compounds would be best described using biphasic rather than “mono-phasic” pK_a values.

Recent developments of our laser-MS system

From left: Aleksei, Signe (in front), Victor, Tõiv

We are glad to say that we have obtained the first promising results with the development of the laser-MS system!

We have done various testing with an existing laser to select suitable laser wavelengths and parameters as well as tested different configurations with mass spectrometers. The latest progress shows that the research project is on the right track.

A big help to these experiments has been Victor Augusto Xavier Da Silveira who joined our project this year. He is a Master’s student of the Excellence in Analytical Chemistry (EACH) programme with a background in chemical engineering and has been a technician of mass spectrometric devices.

Victor, you have done excellent work, thank you for that!

Good job, team! Keep up the good work!

Order of Merit of the White Star – Prof. Hilkka Hiiop

Today it was announced that the president of Estonia, Alar Karis, has honored 148 Estonians or our friends from abroad with national awards, also known as decorations.

It is a great pleasure to announce that the Order of Merit of the White Star was awarded to Prof. Hilkka Hiiop, a valued member of our workgroup! She has been acknowledged for bringing the conservation of cultural heritage into the focus of Estonian society.

The press release can be found here (in Estonian). But to translate some of the words of our president: “On the eve of Independence Day, the Republic of Estonia thanks people with its decorations whose perseverance, selflessness, dedication, ingenuity, or creation are an example to many others and have made Estonia better, more caring, more noticed, and more entrepreneurial.”

Congratulations from all of us to you, Hilkka!

Measurement Uncertainty online course, March 22 – May 3, 2022: Registration is open!

The 2022 edition of the web course (MOOC) Estimation of Measurement Uncertainty in Chemical Analysis will be running from March 22 to May 3, 2022. 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).

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 60 euros.

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

Author: Eliise Tammekivi