Aminoacridines as matrix materials for the analysis of complex samples in MALDI(-)-MS

A highly interdisciplinary study ranging from computational chemistry to cultural heritage has now been published – Experimental and Computational Study of Aminoacridines as MALDI(-)-MS Matrix Materials for the Analysis of Complex Samples, J. Am. Soc. Mass Spectrom. 2021.  

9-aminoacridine (9-AA) is a well-known matrix material used for the MALD(-)-MS analysis. Among the other monoaminoacridines (AAs), only 3-AA has been tested once (in our cultural heritage workgroup) but the suitability of the other AAs was unknown.

To fill this gap, the capabilities of all five AAs were studied by analysing different materials (stearic acid, colophony resin, dyer’s madder, and a resinous sample from a 16th-century shipwreck). Also, a vast range of properties for these aminoacridines were experimentally or computationally characterized (including UV-Vis absorption and fluorescence spectra, proton transfer reactions, crystallization). 

The results demonstrated, that all the AAs are suitable for the MALDI(-)-MS analysis of these materials. Interestingly, 3-AA and 4-AA outperformed the other AAs (including the best-known 9-AA) and were the preferred matrices for the analysis of samples studied in this work.   

 

 

Acidity scale in acetonitrile: 231 pKa values spanning 30 orders of magnitude

The equilibrium acidity scale (pKa scale) in acetonitrile (MeCN) has been supplemented by numerous new compounds and new ΔpKa measurements and has been published in Eur. J. Org. Chem. 2021, 1407–1419 (Open access). The pKa scale now contains altogether 231 acids – over twice more than published previously – linked by 566 ΔpKa measurements and spans between the pKa values of hydrogen iodide (2.8) and indole (32.57), covering close to 30 orders of magnitude. The acids have wide structural variety, ranging from common families – phenols (e.g. picric acid, alizarin, polyhalogenophenols), carboxylic acids (e.g. acetic, benzoic, retinoic and sorbic acid), sulfonic acids, hydrogen halides) to highly special molecules (chiral BINOL catalysts, bis(benzoxazole-2-yl)methanes, polyfluorinated compounds) and superacids (fluorinated sulfonimides, cyanoform, tetracyanopropenes).

Measurement results acquired over the last 15 years were added to the scale and new least squares treatment was carried out. The treatment yielded revised pKa values for the compounds published previously, with the root mean square difference between revised and previous values 0.04, demonstrating very good stability of the scale.

Correlation equations were developed for estimating pKa values for the studied types of compounds in water, DMSO, DMF and 1,2-dichloroethane on the basis of pKa values in acetonitrile. These equations enable predicting pKa values with an average error around or less than 1 pKa unit, which is a sufficient accuracy for many applications.

The scale is expected to be a useful tool for the widest possible research areas in organic chemistry, electrochemical power sources, catalysis, etc.

Registration is now open: Measurement Uncertainty online course starts exactly in one month!

The 2021 edition of the web course (MOOC) Estimation of Measurement Uncertainty in Chemical Analysis will be running from March 23 to May 4, 2021. 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 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 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!

LC-MS Method Validation online course finished with 28% completion rate!

Altogether 791 people were registered from 86 countries. 338 participants actually started the course (i.e. tried at least one graded test at least once) and out of them 221 successfully completed the course. The overall completion rate was 28%. The completion rate of participants who actually started the studies was 65%. All statistics during the five years can be found in the table below.

Year No of registrations No of countries Active participants Completion rate: Overall Completion rate: Participants who started studies
2017 303 61 224 55% 75%
2018 424 71 236 37% 67%
2019 426 70 227 29% 55%
2020 515 77 267 31% 60%
2021 791 86 338 28% 65%

Both the overall completion rate, as well as the completion rate of those participants who actually started the course have stabilized. The latter completion rate can be considered very good by any measure. As has been the usual case with our online courses, the questions from the participants were often very interesting, often addressed things that are really important to analysts in their everyday work. Such discussions made teaching this course a great experience also for us, the teachers!

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

We plan to repeat this course again in Autumn-Winter 2021-2022.

Software to monitor the price of electricity

One of our former group members, Dr. Karl Kaupmees, used to apply programming to chemistry. Now he has moved on to GridIO to develop software that could be used to monitor the price of electricity.

As it is said in the article, we are used to turning on home appliances when we need them to work. However, it would be more efficient if we could heat our house and charge our electric car when it is the least expensive. The company GridIO is working on a device that could solve this problem and make the home appliances “smart”. 

We wish you the best of luck in your new challenges!

Archemy: a brand new interdisciplinary research lab launched at the Chair of Analytical Chemistry

Archemy is the first archaeochemistry lab in the Baltics where archaeology meets with chemistry, geology, biology, medicine, genetics, material sciences, etc. Our group works in archaeological sciences, especially biomolecular archaeology, with a major focus on ancient dietary and health reconstructions, migrations, and provenance studies. Archemy has wide expertise in material culture studies, human osteology, zooarchaeology, and archaeobotany. Our lab is located at the Chair of Analytical Chemistry Ravila 14A-4011. You can read more about us and our work on our website and follow us on our Archemy lab FB page, or contact us at archemy@ut.ee.

Cultural heritage workgroup started with new PRG project!

We are happy to announce that Dr. Signe Vahur’s Personal Research Funding Team grant (PRG) project got funded!

Yesterday, on the 5th of January was the first meeting with the team members of her new PRG project. The main aim of this project is the development of a new MS system for the analysis of cultural heritage objects. This project is highly interdisciplinary, as it brings together researchers from natural sciences (analytical chemistry, physics, engineering) and humanities (conservation science, art history, archaeology). The duration of this project is 5 years.

We will keep you posted with new developments of this very demanding and interesting project!

 

LC-MS Method Validation web course: 788 participants from 86 countries!

On Tuesday, November 24, 2020 the web course LC-MS Method Validation created and organised by our group was launched for the fifth time as a MOOC (Massive Online Open Course). There are 788 registered participants (the largest number ever in this course) from 86 countries, ranging from Bangladesh to Belize and from Sweden to Togo. The 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, 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 a 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.

Estonian National Heritage Board award to Ackermann project!

The members of the Estonian Centre for Analytical Chemistry (including members from our group) have been partnering with art researchers for years in various interdisciplinary projects. One of the first projects for Rode altar in Niguliste church won many awards and the latest collaboration continues that tradition when on the 14th of October Estonian National Heritage Board awarded the team of Ackerman as the best research team!

Congratulations to everybody!

NB! The final exhibition will be in the Niguliste church and available for everybody starting on the 6th of November. It is a unique chance to see the sculptures from the same sculptor that have spent their time in various Estonian churches and never seen each other.

Our on-line LC-MS Method Validation Course 2020-2021: Registration is open!

Validation_of_LC-MS_Methods_Online_CourseWe are glad to announce that the fifth edition of the online course LC-MS Method Validation created and organised by our Analytical Chemistry group is open for registration at the address https://sisu.ut.ee/lcms_method_validation/ !

The course will be offered as a Massive Open On-line Course (MOOC) during Nov 24, 2020 to Feb 05, 2021.

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 course will also be of interest to chromatographists 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. The course is largely based on the two-part tutorial review:

The course materials assembled by the members of our group include video lectures, texts, tables, schemes, practical exercises, and numerous tests for self-testing. In spite of being introductory, the course intends to offer sufficient knowledge and mathematical skills for carrying out validation for most of the common LC-MS analyses in routine laboratory environment. The real-life analysis situations for which there are either examples or self-tests are for example determination of pesticides in fruits and vegetables, perfluoroalkyl acids in water, antibiotics in blood serum, glyphosate, and AMPA in surface water, etc. It is important to stress, that for successfully carrying out validation, practical experience – both in analytical chemistry as such and also specifically in validation – is crucial and this can be acquired only through hands-on laboratory work, not via an on-line course.

Participation in the course is free of charge. Receiving a 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 60 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 the knowledge and skills in analytical method validation (especially when using LC-ESI-MS).