Think Negative: Finding the Best Electrospray Ionization/Mass Spectrometry Mode for Your Analyte
Previously our group has developed extensive ionization efficiency scales in ESI positive and negative mode. Thus far, the comparison between the two modes has only been qualitative. Due to use of different anchor compounds the scales were not quantitatively comparable. To solve this problem and to enable direct quantitative comparison of the two ESI modes we searched for an anchor compound ionizing to the similar extent in both modes. To find such a compound we combined mass spectrometry with laser induced fluorescence measurements (to find out the solvent composition and pH in the ESI droplets), NMR and UV-Vis (to characterize the potential anchoring compounds ionization degree in corresponding solvent). Trans-3(3-pyridyl)acrylic acid was found to be a suitable anchoring compound, if analysed in mobile phase with pH 4.00.
The link between two ESI modes ionization efficiency scales enables the user to choose the most optimal ESI mode for analysis for the analyte in question.
We also compared ionization efficiencies of 33 compounds ionizing in both modes and found that, contrary to general practice, negative mode allows higher ionization efficiencies for 46% of the compounds. For 18% positive mode ESI provides better ionization efficiencies and for 36% the results obtained in both modes are comparable. However, not all compounds can be ionized with ESI negative mode, and some unfortunately also not with ESI at all.
Published in: Piia Liigand; Karl Kaupmees; Kristjan Haav; Jaanus Liigand; Ivo Leito; Marion Girod; Rodolphe Antoine; Anneli Kruve; Anal. Chem. DOI: 10.1021/acs.analchem.7b00096
On May 18, 2017 the MOOC Estimation of measurement uncertainty in chemical analysis offered by University of Tartu finished successfully.
Eventually altogether 363 people registered (270 in 2014, 489 in 2015, 757 in 2016) from 69 countries (a number of participants joined after the start of the course). The significantly lower number of participants is understandably due to the fact that this year for the first time the certificate on paper was not free of charge. 219 participants actually started the course (i.e. tried at least one graded test at least once) and out of them 148 successfully completed the course (141 in 2014, 169 in 2015, 308 in 2016). The overall completion rate was 41% (52% in 2014, 34% in 2015, 40% in 2016). The completion rate of participants who started the studies was 68% (67% in 2014, 60% in 2015, 67% in 2016). The completion rates of participants who actually started the course are nicely consistent over the years and can be considered very good for a MOOC, especially one that has quite difficult calculation exercises, which need to be done correctly for completing the course.
The participants were very active and asked lots of questions. These 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 the overall number of posts to them during the course period reached beyond 300 (!) (overall number of posts, both from participants and from teachers) and the forums are still active and posts are still coming in.
This active participation made teaching this MOOC a great experience also for us, the teachers. The discussion threads gave a lot of added value to the course and some of them triggered making important modifications to the course materials, even during the course.
We want to thank all participants for helping to make this course a success!
We plan to repeat this course again in Spring 2018.
The presentation outlines the recent results by Pilleriin in creating the method for quick, easy and non-destructive classification and semi-quantitative analysis of textiles using ATR-FT-IR spectroscopy combined with chemometric data analysis methods.
She investigated altogether 89 individual textile materials – Wool, Silk, Cotton, Linen, Cellulose acetate, Lyocell/Tenzel, Viscose, Polyester fibre, Polyamide fibre, Polyacrylic fibre, Elastane and their different combinations – and created a discrimination/classification model using principal component analysis (Image on the right).
On the 5th of April 2017 the European Commission and Europa Nostra announced the winners of the 2017 European Union Prize for Cultural Heritage / Europa Nostra Awards, Europe’s top honour in the heritage field.
The project was coordinated by Dr. Hilkka Hiiop from the Art Museum of Estonia. This project also involves several scientists from the chair of analytical chemistry at the University of Tartu, among them Dr. Signe Vahur and her student Krete Saak, and Dr. Riin Rebane, who carried out a thorough material analysis.
The Award Ceremony will be held in Turku, Finland on the 15th of May 2017. During the ceremony, in addition to seven Grand Prix laureates also the Public Choice Award winner will be announced. Everyone has a chance to vote for 3 of their favourite projects, and thereby enter a draw to win a trip for two to Turku and take part in the European Heritage Awards Ceremony on 15th of May. The deadline for casting your votes is the 3rd of May, 2017.
Currently 336 participants from 62 countries are registered. The somewhat decreased popularity of the course is most probably due to the fact that starting from this year certificate of completion on paper is not free of charge (digital certificate is still free). Given this change, we are actually surprised that we still have so many participants! Image on the left shows the countries where the participants come from. As in the previous years, the majority of participants are from analytical laboratories, once again demonstrating the continuing need for training in measurement uncertainty estimation in analytical chemistry.
The full course material is accessible from the web page https://sisu.ut.ee/measurement/uncertainty. Some developments and improvements have been made to the course material, in particular, better description of course organisatsion a self-test on sophisticated uncertainty estimation taking numerically into account the limited selectivity of the technique (potentiometry with ion-selective electrode). Some changes are still in the pipeline. 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 take six graded tests and get higher than 50% score. These tests are available to registered participants via the Moodle e-learning platform.
The online course Estimation of measurement uncertainty in chemical analysis will start its 4th edition on Monday, Mar 27, 2017. 300 participants have already been registered from 58 countries. Registration is still open and all people interested to learn this important topic are welcome to participate!
On Feb 16, 2017 the MOOC LC-MS Method Validation finished successfully.
Altogether 303 people were registered from 61 countries. 224 participants actually started the course (i.e. tried at least one graded test at least once) and out of them 168 successfully completed the course. The overall completion rate was 55%. The completion rate of participants who started the studies was 75%. Both completion rates are all time highest that our group has seen in our MOOCs!
The questions from the participants were often very interesting, often addressed things that are really important to analysts in their everyday work and in several cases led to improvements in the course. This active participation made teaching this MOOC a great experience also for us, the teachers! The discussion threads gave a lot of added value to the course and some of them triggered making important modifications to the course materials.
We want to thank all participants for helping to make this course a success!
We plan to repeat this course again in Autumn 2017.
Friday 27.01.2017 was the last day of the EACH Winter School 2017. It appears to have been a memorable experience for all participants, especially those from southern countries. For example, quite some people had never walked on ice in their life, not to speak about jumping into water from sauna or under ice fishing! (See the previous post).
We were able to experience the best of Sweden – Swedish food, nature and hospitality, which was spiced up and complemented with exotic dishes and participants’ enthusiasm.
The next Winter School will take place in January 2018 in Lyon.
Photos by Jayaruwan and Jonas: group photo and beautiful sunset on Lake Erken.
On Jan 23, 2017, the second Winter School of the EACH programme started in Erken Laboratory (Erken, Sweden). Altogether 34 students from more than 20 countries participate.
The Winter School offers a diverse set of activities to the participants. There are lectures on advanced analytical chemistry topics by top experts, group works and entertainment. Several sessions are presented by industry practitioners. The intense working is counterbalanced by social activities.
Traditionally an important activity in the Winter school is selecting first year students to study tracks. In order to give one more piece of information what the study tracks are about, there was a session of presentations on the first day by second year students on their master thesis topics.
Group Photo (Jayaruwan Gunathilake): in front of the main building of the Erken Laboratory; Photos in the middle (Ivo Leito): Uppsala students presenting their master theses and prof. Jonas Bergquist enjoying their presentation; Photo on bottom left (Ivo Leito): Vietnamese students following the presentation.