New Article Published: Analytical Chemistry

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


Rode Altarpiece Research and Conservation Project wins the EU Prize for Cultural Heritage / Europa Nostra Award 2017

Awards2017-Website&Facebook-share-1200x630On 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.

Among the 29 laureates (from 18 countries) is also the Rode Altarpiece Research and Conservation Project (research category) of the high altar of St. Nicholas’ Church in Tallinn.

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.

Further information on the project can be found on the web page: Rode Altarpiece in Close-up.

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