Measurements and computations of acidity and basicity of strong and superstrong acids (superacids) and bases in organic solvents is among the core research topics at the UT Chair of Analytical Chemistry. In a recent works (Chem. Sci. 2017, 8, 6964-6973.,    J. Phys. Org. Chem. 2013, 26, 162-170.,    J. Phys. Chem. A 2015, 119, 735–743.,    J. Phys. Chem. A 2016, 120, 3663–3669.) the behavior of a number of acids – ranging from weak to strong and superstrong acids (superacids) was examined in three solvents (water, acetonitrile, 1,2-dichloroethane) and in the gas phase. Acidities (pKa values) of a number of different acids including the well-known superacids trifluoromethanesulfonic (triflic) acid, bis-trifylimide (Tf2NH), etc as well as the carborane superacids (closo-carborane superacids), but also weaker acids (HCl, acetic acid, phenol) etc are examined in the above mentioned solvents. pKa of superacids are not easy to find in literature. Trends of acidity changes on moving from water to the gas phase depnding on the on the nature of the acidity centre and the molecular structure are analyzed. The acidity orders are different in water, MeCN, DCE and the gas phase. In some cases – notably, the hydrohalogenic acids HCl, HBr and HI – the differences are dramatic. These three acids are among the strongest known acids in water but have modest acidity in the gas phase. In contrast, 9‑C6F5‑Octafluorofluorene, a weak acid in water (approximately of the strength of phenol) is quite strong acid in the gas phase, beating any of the hydrohalogenic acids.

It is demonstrated that the decisive factor for behavior of the acids when transferring between different media is the extent of charge delocalization in the anion and that the recently introduced WAPS parameter in spite of its simplicity enables interpretation of the trends in the majority of cases. The acidity data together with references to specific publications are collected in the Table below.

Table of pKa valuesa of acids in different solvents.

 

 

 

 

 

 

Acid

H2O

MeCN

DCEb

GP

GP

 

pKa

pKa

pKa

pKa

GA

 

 

 

 

 

 

Fluoradene

11.1

23.90

12.5

238

324.9

Para-Toluenesulfonamide, 4-CH3-C6H4-SO2-NH2

10.21

26.87

15.6

245

334.0

9‑C6F5‑Octafluorofluorene

10.1

18.88

9.0c

220

300.6

Phenol

10.00

29.14

19.6

251

342.3

(C6F5)2CHCN

9.5

21.10

10.3

229

312.4

C6F5CH(CN)COOEt

5.89

17.75

7.5c

230

313.5

2,4-Dinitrophenol, 2,4-(NO2)2-C6H3OH

4.09

16.66

4.7

226

308.6

(CF3)3COH

5.40

20.55

9.2

238

324.0

Acetic acid, CH3COOH

4.76

23.51

15.5

250

341.1

(4-CF3-C6F4)2CHCN

4.4

16.13

6.0

221

302.1

4-NO2-C6H4-CH(CN)2

2.3

11.61

0.3

220

299.5

Saccharin

1.80

14.57

5.5

232

315.9

Picric acid, 2,4,6-Trinitrophenol

0.40

11.00

0.0

219

299.0

(4-NO2-C6H4-SO2)2NH

<-1

8.19

-3.9c

213

291.1

(CF3SO2)3C6H2OH

-2.0

4.48

-6.6c

208

284.2

(CF3SO2)2NH

<-2

0.3d

-11.9c

210

286.9f

(C2F5SO2)2NH

<-2

-0.10

-12.4c

208

283.7

Cyanoform, (CN)3CH

-5.1

5.1

-6.4c

216

294.8

Triflicid, trifluoromethanesulfonic acid, CF3SO2OH

-14.7g

0.70

-11.3c

215

292.7g

Hydrochloric acid, hydrogen chloride, HCl

-5.9g

10.30

0.2c

241

328.1g

Hydrobromic acid, hydrogen bromide, HBr

-8.8g

5.5

-4.4c

233

318.3g

Sulfuric acid, H2SO4

-9e

8.7d

-2.2c

221

301.2f

Pentacyanopropene

-9.02

-2.80

-15.3c

196

267.2

Hydroiodic acid, hydrogen iodide, HI

-9.5g

2.8

-7.3c

227

309.3g

CB11H12H, unsubstituted closo-Carborane superacid

-25h

-17h

-25f

195

266.5f

B12H12H2, unsubstituted closo-Dodecaborate superacid

-17h

-9h

-17f

196

267.5f

CB11F12H, perfluoro-closo-Carborane superacid

-47h

-39h

-47f

156

212.8f

B12F12H2, perfluoro-closo-Dodecaborate superacid

-45h

-37h

-45f

156

213.4f

 

 

 

 

 

 

a Values from http://dx.doi.org/10.1002/poc.2946 unless noted otherwise. There are numerous comments and details to these values. Please see the original articles for details and comments. GA values are given in kcal mol-1. pKa values in the gas phase are approximate and have been obtained from the GA values by dividing with 1.364 kcal mol-1. b Ion pair pKa values relative to picric acid in 1,2-dichloroethane. c Values from https://doi.org/10.1039/c7sc01424d. d Values from http://dx.doi.org/10.1021/jo101409p. e Value from E. V. Anslyn, D. A. Dougherty, Modern Physical Organic Chemistry, University Science Books, Sausalito, 2006. f Values from http://dx.doi.org/10.1021/jp506485x. DCE values have been recalculated from absolute to relative, in order to be comparable with the rest. g Values from http://dx.doi.org/10.1021/acs.jpca.6b02253. h Crude estimates from DCE data by considering that bulk water is by 53 kcal mol-1 more basic than bulk DCE and bulk acetonitrile is by 42 kcal mol-1 more basic than bulk DCE.

 

(This post was initially posted on Feb 2, 2013. On Jan 15, 2017 a number values in the table have been replaced by more reliable values from more recent publications. In addition, some compounds were added to the in order to give a fuller picture. The changes concern only the table. The image has not been changed and should be viewed as illustrative)

_END_

Huian_Liu_in_lab_with_GC_instrumentThe master theses of the EACH programme have usually high practical value. However, this does not prevent them to lead to cutting edge scientific results.

The master thesis of Huian Liu – EACH 2017 graduate from the Lyon study track – titled Gas separation by high pressure gas chromatography using monolithic columns is a good example. At its core the thesis was devoted to investigating the behavior of monolithic GC columns in separation of small hydrocarbons for achieving high efficiency and short analysis time – an important issue in oil refineries.

As an additional value, however, it involved experimenting with a novel detector – vacuum UV absorption detector (VUV detector). VUV detector is an emerging detector in GC, enabling simultaneous detection, identification and quantitation of analytes.

In chromatography there are detectors of two response types – concentration-sensitive and mass-sensitive detectors. The response type is important in planning separation, and especially in quantitation. As a result of Huian’s work it was firmly established that VUV detector is a concentration-sensitive, not mass-sensitive detector. This result was considered scientifically so significant that it was accepted for publication by the number one chromatography journal in the world – Journal of Chromatography A (!): Huian Liu, Guy Raffin, Guillaume Trutt, Jérôme Randon J. Chrom. A, 2017, 1530, 171–175. Congratulations to Huian and the team!

Huian is continuing his studies as a PhD student at UCBL.

 

(Photo: Huian Liu in lab with the GC instrument)

 

Monika_Sandy_Rudolf_MarkoThis June and September, the first intake of students graduated successfully from the EACH programme (See the graduation blogposts at Uppsala, Lyon and Åbo).

Just few months later, 14 out of our 17 fresh graduates have already obtained positions! Some work in the professional/industrial field, some in academic field. Their jobs range from research assistant at a university to project manager at an international corporation. Several have chosen to continue their studies as PhD students. The reflections of some of our graduates on the programme are here:

Marko_Jovanovic

 

Marko, working as project leader in the Industrial Development at Servier (France), writes:
I have spent amazing 2 years in EACH Programme, that represents a perfect balance between studying and travelling. Throughout this period, we had the opportunity to be educated by the experts in the field of Analytical Chemistry. The study track – Industrial Analysis held in France gave me an important insight into the field that I was not so familiar with before I had the opportunity to spend 6 months of the Programme among well-educated and highly-skilled professionals in the company Axel’One, where I was doing my internship. Since Axel’One is a collaborative research platform, I was engaged in several different projects with different companies. This enabled me not only to enrich my knowledge and skills in applied analytical chemistry, but also to significantly expand my professional network. In the end, I was offered a job in France, within a company Servier, as a Project Lead in the Industrial Development.

Monika

 

Monika, working as research assistant at the University of Exeter (United Kingdom), writes:
The Excellence in Analytical Chemistry program was an extremely valuable experience that increased rapidly the course of my career. Taught by highly competent and respected professors it gives the opportunity to gain all the necessary skills in modern analytical techniques. It has been a pleasant, exceptional experience and honor to be a part of EACH!

Monika is simultaneously pursuing doctoral study at Exeter.

 

Sandy

Sandy, now working in the laboratory of the Akademiska sjukhuset hospital in Uppsala, Sweden, writes:
EACH program was so fruitful. It provided me with the skills needed to kick off my career path by providing a wide range of courses delivered by passionate tutors who really care about your success. Moreover, EACH has wonderful activities like a winter school where you can get knowledge and unforgettable social activities. Thanks to everyone who contributes to the success of EACH!

Rudolf

 

 

Rudolf, now a doctoral student at the Örebro University (Sweden), focusing on analytical chemistry of environmental pollutants, adds:
EACH program exposed us to new (study) environments and without doubt provided an invaluable experience. This project offered me a chance to study a specific field in depth. The obtained skills were crucial for pursuing of third cycle studies. All in all, I got more out of the program than I expected in the beginning.

 

 

The success of our graduates is also the success of the EACH programme! This has also been recognised by the European Commission who has decided to extend the funding of Erasmus Mundus scholarships for the EACH programme.

 

Agnes Heering successfully defended her PhD thesis on experimental realization of the unified pH scale

On December 6, 2017 Agnes Heering, an alumna of AMS, the sister programme of EACH, successfully defended her PhD thesis titled Experimental realization and applications of the unified acidity scale.

Her work literally redefines the way the pH of non-aqueous and mixed aqueous solution is understood and measured. The main focus of the experiments was on validating the measurement approach and measuring the unified pH values, i.e. pHabs values, of HPLC mobile phases (eluents). Her work introduces a conceptually new approach of measuring pH of mixed-solvent liquid chromatography (LC) mobile phases and has been published in the Analytical Chemistry journal: Unified pH Values of Liquid Chromatography Mobile Phases. Anal. Chem. 2015, 87, 2623–2630.

Mobile phase pH is very important in LC, but its correct measurement is not straightforward and all commonly used approaches have deficiencies. The new and fundamentally correct approach developed by Agnes enables direct comparison of acidities of solutions made in different solvents, based on chemical potential of the proton in the solutions.

The work by Agnes represents the first experimental realization of the pHabs concept using differential potentiometric measurement for comparison of the chemical potentials of the proton in different solutions (connected by a salt bridge), together with earlier published reference points for obtaining the pHabs values (referenced to the gas phase) or pHabsH2O values (referenced to the aqueous solution). The liquid junction potentials were estimated in the framework of Izutsu’s three-component method.
She determined the pHabs values for a number of common LC and LC-MS mobile phases and formed a self-consistent pHabs scale. This scale enables for the first time direct comparison of acidities of any LC mobile phases: with different organic additives, different buffer components etc. Agnes has developed a possible experimental protocol of putting this new approach into chromatographic practice and has tested its applicability. She has demonstrated that the ionization behavior of bases (cationic acids) in the mobile phases can be better predicted by using the pHabsH2O values and aqueous pKa values than by using the alternative means of expressing mobile phase acidity. Description of the ionization behavior of acids on the basis of pHabsH2O values is possible if the change of their pKa values with solvent composition change is taken into account.

The defence was successful in every respect. Agnes presented very well, answered questions confidently and convincingly demonstrated to everyone that she is really on top of this whole matter.

(Photo: Agnes Heering and prof. Peeter Burk, the chairman of the defence committee, during defence)

 

Todd_Pagano_working_with_EACH_students_in_labDuring Nov 20 to Dec 1 we had the pleasure to host visiting scholar, prof. Todd Pagano from the Rochester Institute of Technology (RIT), USA. He conducted 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.

Todd_Pagano_Lecturing_in_EACH_programmeThe course consisted of lectures, seminars, tutorial sessions and a lab practical. The latter was specifically set up for this course by prof. Pagano and was very much appreciated by students. The analysis that was carried out was determination of caffeine in beverages by fluorescence quenching.

Altogether 23 students (out of them 13 EACH students) participated in the course and their feedback was overwhelmingly positive.

Prof. Pagano is a passionate educator. He was the director 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.

Todd_Pagano_setting_up_lab_practical_in_EACH_programmeBesides the EACH Erasmus Mundus JMD, prof. Pagano’s visit was funded as part of a project by the US Fulbright Specialist programme.

(Images: top left, prof. Pagano working with students in the lab; right: prof. Pagano lecturing; bottom left: prof. Pagano setting up lab practical)

 

LC_MS_Validation_MOOC_Participants_Countries_2017On Tuesday, November 28, 2017 the web course LC-MS Method Validation was launched for the second time as a MOOC (Massive Online Open Course). There are 423 registered participants (by more than 100 more than in 2016) from 71 countries, ranging from Bolivia to Indonesia and from Sweden to Tanzania. 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 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.

It is planned to run this course as MOOC again in autumn 2018.

(Image: Wikimedia Commons)

EACH_Erasmus_Mundus_JMDWe are glad to announce that the 2018 admission is officially open to the 4th intake of the Excellence in Analytical Chemistry (EACH) Erasmus Mundus Joint Master Degree programme!

This international two-year joint master degree programme educates specialists in analytical chemistry well qualified to work in industry (food, pharmaceutical, materials, energy, etc), chemical analysis laboratories (environment, food, health, etc) and research (developing new analysis devices or new analysis methods) worldwide. EACH provides knowledge and practical skills in both fundamental and applied aspects of modern analytical chemistry. Practical internship placement in industry or laboratories is an important part of the training.

The programme is suitable both for students who have finished their bachelor’s studies and want to continue in master’s studies, as well as for working analytical chemistry practitioners wishing to spend couple of years to bring their knowledge and skills to a new level.

The programme features generous scholarships as detailed in the Scholarships and tuition fees page.

The programme is taught by four universities: University of Tartu (UT, coordinator), Estonia; Uppsala University (UU), Sweden; University Claude Bernard Lyon 1 (UCBL), France; and Åbo Akademi University (AAU), Finland. The language of instruction is English, but students will also learn to communicate in one of the languages of the countries involved.

The online application form, admission requirements, deadlines, list of necessary documents, instructions/explanations, as well as contact data for questions are available from the EACH Admission information page.

We wish you all the success in applying!

 

 

JMS_v52_i10_CoverThe Analytical chemistry group at UT recently received a very pleasant and well-deserved recognition: the paper MALDI‐FT‐ICR‐MS for Archaeological Lipid Residue Analysis J. Mass Spectrom. 2017, 52, 689-700 led by research fellow Dr Ester Oras was selected by the editorial board as the cover article for the Oct 2017 issue of the Journal of Mass Spectrometry!

Ester_OrasEster’s research demonstrates that tiny (and to a large extent degraded) food remains on ceramic potsherds, dating back many hundreds of years, can still tell interesting stories about the food practices of our ancestors. The key to these results is clever usage of high-resolution FT-MS with MALDI ion source.

The developed methodology is expected to lay foundation to further studies of ancient food practices in Europe.

 

(Photo on the left: cover of the Oct 2017 issue of the Journal of Mass Spectrometry; photo on the right: Ester Oras)

 

Validation_of_LC-MS_Methods_Online_CourseWe are glad to announce that the second edition of the online course LC-MS Method Validation 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 28, 2017 – Feb 09, 2018. This is the second edition of this MOOC and, differently from the last year’s edition, the number of participants is not limited this time. So, whoever is interested is welcome to register!

This is a practice-oriented on-line course on validation of analytical methods, specifically using liquid chromatography-mass spectrometry as technique, mostly (but not limited to) using the electrospray (ESI) ion source. 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 recently published two-part tutorial review:

The course contains lectures, practical exercises and numerous tests for self-testing. In spite of being introductory, the course intends to offer sufficient knowledge and 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 pesticide analyses in fruits and vegetables, perfluororalkyl acids in water, antibiotics in blood serum, glyphosate and AMPA in surface water, etc. It is important to stress, that for successful validation experience (both in analytical chemistry as such and also specifically in validation) is crucial and this can be acquired only through practice.

The course is free of charge. Receiving 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 web by anyone who wishes to improve the knowledge and skills in analytical method validation (especially when using LC-ESI-MS).

 

DSC_0294Mass spectrometry is currently probably the No 1 technique for determining trace-level components in complex (especially biomed-related) mixtures. The key issues in such applications are sample preparation, sample introduction to MS and ionization of components of interest (analytes). Big efforts are continually made to improve any of them.

In his recent development – Sponge sprayMax Hecht, an AMS graduate, now PhD student at UT attempts improvements in all of the above issues. The elegant approach proposed by Max utilizes a volumetric sampling device – a hydrophilic sponge, which after absorbing a predetermined amount of sample (e.g. blood or urine), can be directly used for sample introduction to MS and ionizing the analytes.

The seriousness of the work has been demonstrated by the fact that it was accepted for publication by Analytical Chemistry, the top journal in the field. The published article Sponge Spray – Reaching New Dimensions of Direct Sampling and Analysis by MS is now available from the journal website.

Further developments of this approach may lead e.g. to fast medical diagnosis MS methods that, contrary to the current situation with MS in medicine, could be applied as “bed-side” diagnosis tools in hospitals.

(Photo: Max Hecht working with the sponge spray ion source)