The recent research news of the University of Tartu included also the results of our newest article: Quantitative mineralogical analysis of clay-containing materials using ATR-FT-IR spectroscopy with PLS method, published in Anal. Bioanal. Chem. The other fresh news focused on the collaboration between enterprises and researchers, cancer metastasis, and vocalizations. The short descriptions of the studies can be found on the poster or on the UT website.
In English: Last week, on the 20-24 of September, Reasearchers’ Night festival 2021 took place all over Estonia. Our archaeochemist Dr. Ester Oras gave an interesting audio lecture about the eating habits of people living in the region of current Estonia in the distant past. This topic starts with the first findings related to eating habits from the Mesolithic period and arrives at the Middle Ages. During the whole lecture, she illustrates how chemical analyses can be used for the analysis of archaeological objects. Here is the audio lecture in Estonian, but there’s also a blog post in English on a similar topic.
Eestikeeles: Eelmisel nädalal (20.-24. septembril) toimus üle Eesti 16. Teadlaste Öö festival. Meie arheokeemia töögrupi juht Dr. Ester Oras andis festivali raames huvitava heliloengu, kus ta rääkis mida inimesed sõid kauges minevikus praeguse Eesti aladel. Ester selgitab inimeste toitumisharjumisi Mesoliitikumi ajajärgust (kust pärinevad esimesed toiduga seotud leiud praeguse Eesti aladel) Keskajani välja. Kogu loengu vältel kirjeldab Ester ka seda, kuidas keemilised analüüsid aitavad mõista arheoloogilisi leide. Mainitud eestikeelse heliloengu leiab siit, kuid samal teemal on olemas ka ingliskeelne blogipostitus.
In the recently published paper including the members of our Analytical Chemistry Chair, a method was developed to detect amino compounds with diethyl ethoxymethylenemalonate (DEEMM) derivatization in neutral loss scan mode by liquid chromatography-tandem mass spectrometry (LC-MS/MS). Amino compounds react with DEEMM, and the derivatives lose a neutral ethanol molecule [M+H-46]+ from the parent ion upon collision-induced dissociation (CID) fragmentation. Therefore, it is possible to employ neutral loss scan (NLS) mode of the triple quadrupole mass analyzer.
The first part of the work was dedicated to the development of the method, such as testing different solvents and quenching reagents in order to obtain a cleaner chromatographic profile. Hydroxylamine was chosen as the quenching reagent, considering the retention time of its DEEMM-derivative and its solubility in the solvent employed (0.1 M HCl in 30% methanol).
Finally, the developed method was applied to an extract from the plant species Carduus nutans subsp. macrocephalus (Desf.) Nyman, in which 18 amino acids and 3 biogenic amines were identified for the first time in this plant species. The method can be applied to different matrices for the detection of known and unknown amino compounds.
Here you can find the 50-day free access to the article.
On the 24th of August, 2021, Merit Oss successfully defended her PhD thesis titled “Ionization efficiency in electrospray ionization source and its relations to compounds’ physico-chemical properties”
The thesis by Merit revolves around ionization efficiency in electrospray ionization (ESI) MS. The main aim was to gain a better understanding of the relations between different molecular properties of compounds and the signal intensities of their ions in ESI-MS. During this study, a large number of ionization efficiency values were obtained. Eleven molecular parameters were taken into account for estimating their importance for evaluating the compound’s ionization efficiency in ESI. It was concluded that in the studied solvent system, a compound’s ionization in the ESI source is determined by its basicity, molecular size, and hydrophobicity/lipophilicity. The results showed that the obtained models for estimating compounds’ ionization efficiency can be used for approximate prediction.
Congratulations, Merit! We wish you all the best for your future.
Our group recently published a new article: Classification of archaeological adhesives from Eastern Europe and Urals by ATR-FT-IR spectroscopy and chemometric analysis. Archaeometry, 2021, 1–18.
In this study, 100 adhesive samples, collected from hafting tools and ceramic containers as well as some adhesive lumps were analyzed using ATR-FT-IR in combination with PCA-based DA classification. The aim of this study was to discover the capabilities of ATR-FT-IR-DA classification as a potential screening method for the identification and grouping of different archaeological adhesive samples, and subsequently reduce the use of laborious GC-MS analysis.
100 archaeological adhesives were classified into 3 groups: birch bark tar without major additives (72), birch bark tar with additives (13) and minor/non birch bark tar samples (15). Birch bark tar containing adhesives were separated from minor/non birch bark tar samples. Samples identified as birch bark tar without major additives were further classified possibly by their location, age or cultural specific manufacturing practices. The classification results were confirmed by GC-MS analysis of 9 archaeological samples selected from three compositional groups.
The study proves that ATR-FT-IR-DA classification is a non-destructive, rapid and reliable pre-scanning method for analyzing archaeological adhesives, especially suitable for small samples. Based on the results of ATR-FT-IR spectroscopic analysis, DA classification can help further distinguish samples with different backgrounds such as sample age, initial production, environmental conditions and site-specific preservation. GC-MS analysis could be used as a supplementary/confirmatory method to investigate samples with complex components and provide archaeological DA references for future research.
The full text can be found here.
On the 20th of May, 2021, Astrid Darnell defended her PhD thesis titled “Computational design of anion receptors and evaluation of host-guest binding“.
In the thesis by Astrid, the main aim was to study possible new receptor molecule candidates with computational methods. This could improve the design of receptors used for the detection of various important anions (including glyphosate dianion and small monocarboxylate anions).
The suitability of the COSMO-RS method was tested for studying receptor molecule and anion binding. It was also demonstrated that COSMO-RS was shown to predict correctly the most stable conformers of the majority of the studied molecules.
The effects of receptor and complex geometries and the spatial matching between host and guest species on the binding affinity of large, structurally complex receptors was investigated towards a selection of analytically interesting carboxylate anions. A number of these receptor structures are now being investigated for practical applications as real carboxylate anion sensors in the form of SC-ISEs.
The final part of the study investigated the applicability of isothermal titration calorimetry (ITC) experiments for the determination of the thermodynamic parameters (e.g. reaction entalphy ΔH) of host-guest binding reactions. Low-volume ITC experiments were found to be applicable for the study of low-affinity host-guest binding reactions and the combined standard uncertainty for reaction entalphy determination for these experiments is in the range of 1-2kJ/mol.
Congratulations to you, Astrid!
On May 13, 2021, the online course (MOOC) Estimation of measurement uncertainty in chemical analysis offered by the University of Tartu finished successfully.
Eventually, altogether 950 people registered from 97 countries. 501 participants actually started the course (i.e. tried at least one graded test at least once). The overall completion rate was 33%. This, as well as the participating rate, was the lowest (53%) we have seen. However, the completion rate of the participants who started the studies was 63% with 314 successfully finished participants. This result can be considered very good for a MOOC, especially for one that has quite difficult calculation exercises, which need to be done correctly for completing the course. All statistics during the 8 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 close to 400 (!) (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 2022.
Yesterday, on the 7th of May, Associate Professor emeritus of physics Matti Laan gave a highly interdisciplinary lecture about laser cleaning in the field of cultural heritage.
On this project, Dr. Laan (presenting his lecture in the picture on the right) worked with the late Associate Professor emeritus of chemistry Tullio Ilomets. Dr. Laan gave an exciting lecture about different lasers (e.g., Nd:YAG, XeCl, Er:YAG) and which of them is most suitable for laser cleaning of various artefacts (such as paintings or sculptures). For this laser ablation is used, which removes any undesired material (including ageing products and materials from previous conservation works) layer by layer.
Most of the listeners participated via the Zoom platform – over 70 physics, chemists, conservators, material scientists, and people from other disciplines joined in this interdisciplinarity lecture. The lecture was organised by our Cultural Heritage workgroup, Institute of Physics, and The Estonian Academy of Arts in the framework of Dr. Signe Vahur’s PRG1198. The recording (in Estonian) can be found here.
On Apr 29, 2021 the webinar “Mobile Phase pH in Liquid Chromatography” took place. Altogether 101 people participated from 41 countries, ranging from Portugal to Philippines and from Peru to Nepal.
It is well known that in liquid chromatography, mobile phase pH is an important parameter, significantly affecting the retention of acidic and basic analytes. Yet, mobile phase pH is tricky to measure because mobile phases are usually aqueous-organic mixtures and in the case of gradient elution mobile phase composition gradually changes during elution. The topics covered during the webinar were:
— Different possibilities to express pH in liquid chromatography (LC)
— Unified pH (pHabs): the concept and measurements methods
— The applications and limitations of different pH expressions in LC
Numerous questions were asked by the participants that indicated the importance of the topic and the need for a more robust conceptual framework for handling the topic of pH in liquid chromatography. Contributing to this, via the pHabs concept, is one of the aims of the UnipHied project.
The webinar was organized in the framework of the PRG690 project from the Estonian Research Council and the UnipHied project (www.uniphied.eu), which is funded from the EU’s EMPIR programme, co-financed by the Participating States and from the European Union’s Horizon 2020 research and innovation programme. Additional support from: EU Regional Development Fund (TK141 “Advanced materials and high-technology devices for energy recuperation systems”) and Estonian Center of Analytical Chemistry (www.akki.ee)
Our group recently published a new Open Access research article – Quantitative GC-MS Analysis of Artificially Aged Paints with Variable Pigment and Linseed Oil Ratios, Molecules 2021, 26 (8), 2218.
In this freely accessible publication, seven sets of artificially aged paints prepared from a pigment (chrome oxide green, natural cinnabar, Prussian blue, red ochre, hematite + kaolinite, zinc white, or yellow ochre) and linseed oil were analysed with GC-MS. One of the main aims was to study if the pigment concentration in the paint samples affects the drying of the linseed oil.
The palmitic acid to stearic acid ratio (P/S), azelaic acid to palmitic acid (A/P), and the relative content of dicarboxylic acids (∑D) showed, that besides the type of the pigment, also the concentration of the pigment can influence these values that are commonly used to identify the type of the oil or to characterize how dried is the sample.
The absolute quantification of stearic acid (see figure on the right) showed that the drying of all paint sets (except for zinc white) were influenced by the pigment concentration. Therefore, this is another factor that needs to be taken into account when studying aged oil paints.
