No sample pretreatment?

Do you want to screen the pesticides presence on your orange? Or do you want to determine if person has used illegal drugs? Or maybe you want to determine the contamination level of trees in the park across the street?

How many sample preparation methods do you need for this? The answer is simple. Just one.

You need a PSI/MS. This means a mass-spectrometer (MS) with a paper spray ionization (PSI) source.

Paper spray was invented approximately 5 years ago in Prof. G.R. Cooks lab. This is a technique that allows to analyse samples that have been collected on a paper with MS.

A PSI/MS setup. Author Hanno Evard.

You can analyse dried blood spots and determine metabolites indicating some disease or determine doping chemicals. Just from this one small blood spot. The beauty of the method is that you really do not need to do anything more than place the blood spot bunched out from the collection paper to the cartridge (placed in front of the MS entrance and to which the ionization voltage is applied to) and add solvent. Both sample preparation and ionization occurs then on the paper and in the spray. Sample preparation can be modified by choosing different paper type (chromatographic papers, eg containing silica or C18 modified silica).

I our lab we have mostly used PSI for pesticide determination. The easies application is for pesticides that are located on the peel of the fruit (the ones that are applied after harvesting). For example thiabendazole and imazalile on oranges, lemons, grapefruits etc. You just need to wipe the peel of the fruit with a paper wetted with solvent and put this paper into PSI/MS. It is a bit trickier for compounds that have been applied during cultivation. For these compounds a slice (or a mush) onto the paper and then apply the solvent.

You can find more about our work on paperspray here.

Are all ESI/MS instruments the same?

The second paper on my students Jaanus Liigand master’s thesis was published recently. During his master’s he effectively showed that ionization tendencies of analytes in ESI source are independent of the source design and mass analyser of the 

Altogether 15 compounds with varying properties were measured on 5 instruments (here and in Lyon) and two solvent systems. The statistical treatment (t-test and correlation analyses) results showed that there is no reason to expect large variations between analyte responses between instruments.

Importance of this work? (1) Relating ESI/MS responses with analyte properties is possible (we do not have to take into account source or instrument parameters). (2) Ionization efficiencys already available in the literature are universal and can be used by groups having different instrumentation. 

So to return to the original question, of course different instruments have different sensitivity and many of them may work under very different conditions (voltages, gas flow rates and temperatures) but the large picture for ESI/MS ionization stays the same.

Future perspective? Of course different solvent systems have different effect on ionization efficiencies (protonation, adduct formation, etc) and unfortunately scientist can still only generally predict and explain these effects.

Link to the paper

Applying for Marie Curie fellowship: my proposal submitted

Yesterday I submitted my proposal for becoming a Marie Sklodowska-Curie fellow. So if everything goes as hoped I will be collaborating with Prof. Christoph Schalley group in Free University of Berlin from the next schoolyear. My project there will be about supramolecular chemistry, more precisely on rotaxanes and molecular machines based on rotaxanes. It will introduce me a whole new world of opportunities that exist in supramolecular chemistry. I am really excited about this stay, though it is not certain jet.

I would like to comment on some things that I have learned about myself and about applying during this process. First of all, few years ago I was sure I never want to go to post-doc. There were several reasons. I had my aims that could at that moment of time be fulfilled here in University of Tartu. This has changed, I feel the need to learn some new tricks to reach higher, to be more effective and to widen my collaboration circle. Secondly I have always been very keen on my family. My stay in Helsinki during my doctorate thought me that far away from home (alone) can be somewhat depressing. Though I have grown and also Tauri is now able to come with me to Berlin, so this hard part can be handled. I am really grateful that Tauri is willing to take this effort for my dreams and take a break in his career.

Actually the fact that this proposal is now submitted sounded unrealistic to me in April. Everyone who had either applied for MSC or had heard anything about it told that it is very-very-very (I should probably but an exponent here) hard. And to be honest the form itself also felt quite complicated in the first place. But as the discussion with Prof. Schalley went further a plan that I felt comfortable with was put together and then it wasn’t that complicated to put it down on paper. I am also very thankful to everyone who helped me during this period – starting from discussions on the topic down to taking up some of my duties so that I would have a bit more time to focus on the proposal. Thank you all very much!

What I would like to say to everyone who will be applying to MSC or something similar, even though it seems hard in some point, writing the proposal can really help you. During this period I have written to numerous people I did not even know about before, aiming to gain some information (mostly about how things will be organized in FU when I start my fellowship). And though it seemed a bit weird to me in the first place that I am asking people about things that are not even certain jet, I started feeling must more confident about the success of my stay. Due to these interactions, I hope, I have a more realistic picture what happens when I arrive in Berlin. Which on the other hand has made me feel that it is a right thing to do and I really want to do it.

Another important thing is the influence I have already had. During writing this project I have to admit I read more papers then probably during the whole year before. Which, in the beginning seemed like an ocean, but though I still probably haven’t read a fraction of papers related to my topic in Berlin I have already found a lot of interesting stuff that also is related to my tasks (scientific and partially also teaching) today. And these came up from the papers I would have never been searching from.

I will keep my fingers crossed until the time results of this proposal will become available (Feb 2016).