New publication – retention studies in C18 column using novel fluorinated eluent additives

It is essential to understand the interaction between the analyte, mobile phase and the column chemistry for the best possible separation of molecules. Of all three, the mobile phase in HPLC is the easiest to modify and thus, usually contains different eluent additives or buffers. While using mass spectrometry undoubtedly increases the variety of analytes possible to detect, it also introduces limiting factors such as the requirement of the volatility of the eluent. Most common additives in LC-MS systems are formic and acetic acid, their ammonium salts as well as ammonium bicarbonate. In our recent paper, we have proposed novel – fluorinated, eluent additives (hexafluoroisopropanol, hexafluoro-tert-butyl alcohol, trifluoroethanol as well as nonafluoro-tert-butyl alcohol and perfluoropinacol).  Their influence was shown on rather simple exemplary molecules, which are widely spread over different logP values, containing protonated and deprotonated acids and bases. All novel fluorinated eluent additives demonstrated a strong influence on basic polar analytes in basic medium – they drastically increased retention. A decrease in retention was observed for acidic analytes when these novel eluent additives were used.

Moreover, current research displays a comprehensive overview of retention mechanisms for nonafluoro-tert-butyl alcohol and is the first time ever when perfluoropinacol has been introduced as eluent additive for reversed phase chromatography. Additionally, the influence on MS signal was studied when fluoroalcohols were used as eluent additives. This is also the first time when the absolute pH (pHabs) scale was used for expressing the mobile phase pH.

Current fundamental research forms a basis for a better understanding of the influence of fluoroalcohols as eluent additives and will help in the assay development in a wide range of applications.

This work is part of a larger endeavor – to promote a wider usage the unified pH scale (pHabs) by the research and technology communities, which is currently in progress via the UnipHied.

The UnipHied 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.

 

 

New publication – Instrumental techniques in the analysis of natural red textile dyes

A wide variety of different dyes, complex composition of natural dye sources and low concentrations in samples make the identification of textile dyes challenging. In our cultural heritage group, work has been done for years to overcome some of these problems. Using seven different red dye sources and five instrumental approaches, a method for the analysis of textile dyes has now been developed in our lab to study different archaeological findings, museum artifacts, and other textile pieces. More about the results can be found in the article published in the Journal of Cultural Heritage by P. Peets, S. Vahur, A. Kruve, T. Haljasorg, K. Herodes, T. Pagano and I. Leito.

The usefulness of this developed method has been proved by analyzing several case-study samples from Estonian National Museum, KANUT, and private collections. Thanks to the multiple instrument combination and especially the usage of high-resolution mass-spectrometry, it was also possible to identify synthetic organic dyes without the use of any standard substances.

17th Nordic Mass Spectrometry Conference in Espoo

In the last week of August, the 17th Nordic Mass Spectrometry conference was held in Espoo, Finland. With around 150 participants from Nordic countries, the conference covered various different topics within the field of mass spectrometry.

Anneli making her presentation at the 17th NordicMS

From our group, Anneli Kruve presented some of the most recent results in the field of quantitative suspect screening for pesticides and mycotoxins. Riin Rebane presented a poster about analyzing metanephrine (MN) and normetanephrine (NMN) and also about unusual matrix interferences related to the analysis (results have been published here). Artur Gornischeff presented some very exciting results on the ionization studies of derivatized amino acids which have also been published here.

  • Riin with her poster
  • Artur with his poster

NordicMS is a mass spectrometry conference taking place every three years and hosted in turns by nordic countries. This time it was Finland’s turn. The three-day conference had roughly 150 attendees; as expected, primarily from Finland and other Nordic countries. The conference covered all major areas of application of mass spectrometry: food characterization, metabolomics, drug discovery, proteomics, doping discovery and forensics. Topics covered analysis from the sea bottom (Hanna Niemikoski’s presentation about the identification of novel chemical warfare agents) up to the sky (Kari Hartonen’s presentation about sampling from air with drones).

The conference showed that even in the small circle of Nordic countries the research in the field of mass spectrometry is diverse and every mass spectrometry enthusiast will find his or her spot in the field.

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.  

Successful Master’s defense about ValChrom software

Thesis: “Software Tool for Validation of Chromatographic Analytical Method” by Kodjovi Hippolyte-Fayol Toulassi

Kodjovi Hippolyte-Fayol Toulassi defending his thesis

The aim of the work was the development of the back-end for ValChrom software. It was jointly supervised by professor Marlon Dumas (Institute of Computer Science) and Koit Herodes and Asko Laaniste (Institute of Chemistry). Kodjovi successfully presented both the chemistry and computer science aspects of the thesis, gaining praise from the supervisors and the opponent.

The software

ValChrom is a software tool developed with the aim of easing the burden of analytical chemists at chromatographic method validation. In ValChrom the user chooses the validation approach (Kodjovi implemented 3 guidelines: ICH, EMA bioanalysis, and Eurachem) and software recommends a respective experimental plan.

After importing experimental results, ValChrom calculates results and generates a report. Feedback and suggestions are welcome at valchrom@ut.ee.

We are happy to introduce: Dr. Piia Liigand and Dr. Jaanus Liigand

In August, additionally two of our PhD students, Piia Liigand and Jaanus Liigand, successfully defended their PhD theses. Both Piia and Jaanus worked intensively and successfully on understanding the ionization process in electrospray ionization source (ESI) and applying this knowledge for quantifying compounds with LC/ESI/MS without standard substances. Congratulations to the fresh doctors! Piia is continuing as a lab manager in TBD-Biodiscovery and Jaanus continues his scientific career at the University of Alberta in Prof. Wishart group.

On 15th of August, Piia Liigand defended her PhD thesis on “Expanding and improving methodology and applications of ionization efficiency measurements”. The opponent of Piia was Prof. Dr. Susan D. Richardson from the University of South Carolina. Over the last four years, Piia has contributed significantly into the development of ionization efficiency measurement methodology. She has been able to develop a method for measuring the ionization efficiencies for both small molecules as well as oligopeptides. Most of all, she has shown that the predicted ionization efficiencies can be applied for drug and drug-a-like measurements in the biological matrices. And, last but not least, she has pulled together a large number of response factors from the literature and shown that these values are in good agreement with each other in spite the, sometimes observed, contradicting conclusions.

Piia with her supervisors Dr. Karl Kaupmees and Prof. Anneli Kruve and opponent Prof. Susan Richardson

Jaanus Liigand defended his PhD thesis on “Standard substance-free quantification for LC/ESI/MS analysis based on the predicted ionization efficiencies”. Prof. Dr. Jonathan Martin acted as an opponent of the defense. During his PhD studies, Jaanus has worked hard on understanding the mechanism of electrospray ionization in LC/ESI/MS; primarily understanding how the structure of the compound and the eluent used in the analysis influence the ionization efficiency. Jaanus has verified, based on the largest set of ionization efficiencies measured so far (roughly 400 compounds), that the more hydrophobic compounds and more basic compounds tend to have a higher response in ESI positive mode. From the mobile phase point of view, both organic solvent content, pH of the buffer, and buffer composition, influence the ionization efficiency in ESI/MS. In general, higher organic solvent content and lower pH result in higher ionization efficiency and, therefore, a higher response in positive mode ESI/MS. Also, he investigated how well are the ionization efficiency values measured on one instrument transferable to other instruments and found that with the aid of 5-6 common compounds the ionization efficiency values can be transferred from one instrument to another. Combining these promising results and machine learning approaches Jaanus has been able to develop a truly universal approach for applying ionization efficiency predictions for quantification in suspect and non-targeted LC/ESI/HRMS analysis.

Once more – congratulation to you both!

Synthesis and characterization of novel phosphazene-based indicator molecules

On August 22, 2019 Sigrid Selberg successfully defended her PhD thesis titled Synthesis and properties of lipophilic phosphazene-based indicator molecules.

The dissertation presented by Sigrid Selberg is focused on the design and synthesis of a family of highly lipophilic phosphazene based indicators. 16 new phosphazene based indicators where phosphazene structure is extended with an azo group or with 4- (trifluoromethyl)coumarin backbone were synthesized and characterized, indicators are active in both visible absorption and fluorescence. These compounds are highly lipophilic in both neutral and protonated form, therefore, the synthesized compounds have all the desired and suitable properties to employ them in the design of an optical pH sensor. For the first time, alkyl and aryl phosphazenes are used for this purpose.

In addition, the original approach for quantifying acidity/basicity of lipophilic molecules in water-immiscible media that is at equilibrium with aqueous phase is developed and applied in the determination of biphasic pKa values of some of the synthesized compounds.

Congratulations to you, Sigrid!

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.  

EACH is featured in Analytical and Bioanalytical Chemistry!

The educational section of the leading analytical chemistry journal Analytical and Bioanalytical Chemistry, the ABCs of Education and Professional Development in Analytical Science has published a paper about the EACH programme: EACH (Excellence in Analytical Chemistry), an Erasmus Mundus Joint Programme: progress and success

The EACH programme is an Erasmus Mundus Joint Master Degree programme coordinated by our group. It has become one of the leading master’s degree programmes focusing on analytical chemistry within its short existence. The programme is run in cooperation by four top European universities: in addition to the coordinating university, the University of Tartu (first-year university), also Uppsala University (Sweden), Åbo Akademi University (Finland) and University Claude Bernard Lyon 1 (France) are involved as second-year and specialisation institutions.

The paper gives a comprehensive overview about the EACH programme, including a detailed overview of what EACH is, what kind of topics are taught during the first study-year at the University of Tartu, what is the nature of the different study-tracks (specialisation during second study-year either in Sweden, Finland or France), what extra activities, such as internship and winter school the EACH programme offers. The paper also gives an explanation on why it is necessary to have such a programme like EACH, and how to be a part of the EACH experience.

One section in the paper is dedicated to the impact of the EACH programme – with the four years that the programme has accepted students, it has reached a lot of countries and the employability rate of the graduates is almost 90%.

This Autumn, the fifth intake of EACH students is starting their studies at the University of Tartu, expanding the blue areas on the map presented above even more.

For more information on the EACH programme, please see the programme’s webpage and also the newly published paper.

18th International Conference on Density-Functional Theory and its Applications

The conference was held with the participation of 190 scientists from 36 countries representing the 5 continents during 22-26 July 2019 in the University of Alicante, Alicante, Spain. One of our group members, Dr. Ali Ghiami-Shomami, presented a poster during this conference. The presented topic, “DFT and TD-DFT Studies of Some Aminoacridines as Matrices in MALDI-MS”, is an effort towards exploring the factors influencing matrix performance in MALDI-MS technique using computational chemistry and in collaborations with our experimentalists. Some visitors appreciated the work and found it interesting. They emphasized that the MALDI-MS technique is very tricky and therefore, finding some insights about it from computational chemistry is valuable. More information about the conference can be found here: www.dft2019.es