We will be in IMSC

A small part of our group is going to International Mass Spectrometry Conference from 20th to 26th of August in Toront and present the latest results of our studies. The results are so hot that these are not yet available in the journals:

M-T-053 pH effects on electrospray ionization efficiency Jaanus Liigand
W-T-019 Ionization efficiency of oligopeptides and small hydrophilic molecules in ESI/MS Piia Liigand
W-T-137 Predicting concentrations of small molecules without standard substances in LC/ESI/MS via ionization efficiency scales Anneli Kruve

See you in Toronto .... or after that! We will definitely report the coolest talks and posters and how it went for us!

NonTarget2016

Today the importance of environmental analyses has been generally accepted. However conventional environmental monitoring programs are somewhat limited in scope as these programs only search for compounds that have been previously found to exist in contaminated samples. These compounds make up only a fraction of compounds that may be present in target samples overall. In addition to previously found compounds there is a large number of contaminants we are not aware of and for sure some of these compounds are of importance. These compounds have not yet made their way to the emerging contaminants lists.

The lack of these monitoring programs comes from the fact that with the conventional analytical techniques it is even impossible to monitor “everything” as most of the techniques require standard substances for analyses. However if a compound has not yet been identified it is also unlikely (if not impossible) to have a standard for this substance. Currently the importance of analyses of unknown compounds been increasingly noticed. The detection of such unknown compounds is called non-target analyses referring that there aren’t any target compounds, which are specifically looked for. Such non-target analyses can today almost only be done with high-resolution mass spectrometry (HRMS). The beauty of HRMS data compared to conventional target analyses is that you can go back to your data and re-examine if one or another compound was in the sample at any time. This could be done even years later when we have a lot more information on the contaminants..

NonTarget2016, picture from www.eawag.ch

From 29th of May until 3th of June a NonTarge 2016 conference was held in Ascona, Switzerland, specifically dedicated to such analyse. Our Master’s student Gunnar Printsmann who has started to study the organic pollutants in Estonian groundwater received a stipendium to this Europe’s largest conference specifically dedicated to non-target analyses.

In the conference there were present most analytical laboratories dealing with non-target analyses today. In general, it was proposed that approximately 5-10% of the HRMS peaks observed in spectrum can actually be identified via non-target analyses. However, several institutions are working to improve this situation. One thing of urgent need is the list of suspect substances. During last year we have tried to conduct our own suspects list of pesticides, detergents, pharmaceuticals, industrial chemicals etc. Similar lists are also available or being developed under names Tracefinder, NORMAN, etc. Another software that is being developed in several places and which is of great interest also for other MS users not only in non-target screening is the MS/MS transitions predictor. 

We hope to report on Estonian ground water non-target analyses in a near future.

What ions to expect in mass-spec?

One thing that we often do in Testing Centre of University of Tartu is the analyses of the synthesis products for different labs/companies. Usually these compounds are brand new, without any standard substance available. The aim of these analyses is to confirm the identity of the product. What is often puzzling about this type of analyses is that usually it can only be assumed what kind of ions would be formed of the compounds in electrospray. For example will it be a protonated molecular ion, sodium adduct, dimer or something else? Though there are some general ideas and also intuition helping mass spectrometrist’s there is no general guidance. My student Piia focused on the ions formed in negative ESI mode in her first study. More precisely differentiating between compounds forming anions and dianions. Altogether she studied 29 compounds with at least two acidic sites, but only 9 of these gave doubly charged ions in mass spectra. Interestingly the compounds giving multiply charged ions was not related to the acidity of the compounds: there were strong acids not giving multiply charged ions and week acids giving multiply charged ions. The mechanism for this interesting phenomena was revealed by the help of linear discriminant analyses. It turned out that to produce multiply charged ions the compound has to have a suitable combination of acidity and hydrophobicity. For example the strong acids that are quite hydrophilic (and become even more hydrophilic after dissociation) do not reach the ESI droplet surface and therefore can not be ejected to the gas phase for analyses with mass spectrometer. The mistery between ions observed in positive ESI/MS mode (molecular ions, different adducts and multiply charged compounds) is yet to be solved. 

DOI: 10.1007/s13361-016-1384-2

Neonicotinoides in Estonian honey?

Our PhD student Asko Laaniste carried out an extensive study of neonicotinoides in Estonian honey samples gathered over ten years. One of the studied neonicotinoides, thiacloprid, was identified in several samples. It was observed that the fraction of samples containing thiacloprid increased from year to year, reaching up to 60% in samples form 2012. At the same time also the amount of thiaclopride imported to Estonia has increased from year to year. Our stability test showed that thiacloprid is persistent in honey and it can be assumed that these results are not influenced by the decomposition of analyte within years.

Geographical distribution of collected honey samples in Estonian counties is shown bellow. In the brackets the total number of samples acquired from corresponding region is shown (over years). The percentage shows the number of samples containing thiacloprid.

For more see DOI: 10.1080/03601234.2016.1159457

MOOC on LC-MS method validation

Already in last spring when we were writing the tutorial review on LC/MS method validation Ivo introduced us the idea of making a MOOC (massive open online course) on the same topic. By that time he had launched the first MOOC of our institute that has had hundreds of students so far, on such complex topic as measurement uncertainty.

In summer we started putting some first ideas on the “LC-MS validation course” to the paper and in autumn we started doing some first videos for clearing our ideas. By now we have been to the studio several times already and have a significant amount of course videos ready. We will cover all important aspects of method validation in the course: Trueness, Precision, Accuracy, Linearity, LoD and LoQ, Selectivity, Robustness etc. You are all welcome to post ideas or topics of specific interest! 

So we are anxiously waiting for the course to be ready by the end of spring and to launch it in September.

Optimizing sample pretreatment: temperature

In a recent semester I have been involved in several training activities. The most important of these have been the training day for water analyses laboratories organized by EKUK and the practical aspects of working in the laboratory by TÜ Katsekoda.

My lecture/seminar in the first training was about sample matrices as the source of uncertainty. In this lecture the main idea was to show how large uncertainty source may a matrix actually be. As I have been dealing with matrix effects since my masters thesis this is a very interesting point to me. On the practical aspects of working in the laboratory course my major topic was preparing samples for analyses.

Whether considering uncertainty or trueness it ends up with the understanding that a good sample pretreatment is a base for a good analytical method. It seems like an ongoing discussion on whether liquid-liquid extraction of solid phase extraction is a technique providing more possibilities for efficient sample prep. However, what I have often observed in the trainings and lectures is that one important parameter influencing sample extraction, that people do not come up with, is temperature.

Common knowledge is that higher temperatures are advantageous for extracting analytes from solid matrices and in these cases higher temperature helps to break the “bonds” between analyte and matrix. But what is not that often considered is the temperature effect on liquid-liquid extraction.

We know that water properties strongly depend on the temperature. Based on the NISTdatabase the dielectric constant of water ranges from 87.7 to 55.7. The latter value is more similar to acetonitrile then to “water” as we consider it under standard conditions. This means the enthalpy of solvatation for different species changes remarkably with temperature. For example Z. Congliang et al has observed that octanol-water distribution coefficient of an antibiotic sulfamethoxazole is reduced 5 times while working at 45 °C instead of room temperature. And for extracting the sulfamethoxazole from water with octanol the recovery would drop from 89% to 61%. Unfortunately data for lower temperatures are not available to evaluate if lower temperatures could result in higher recoveries. These effects are larger for compounds with low distribution coefficients and therefore with lower recoveries.

It is even interesting to consider how much could year-around room temperature fluctuation influence the extraction?

Recognition of Piia and Jaanus on scientific works competition

This week two of my students have been recognized by different organizations for their outstanding scientific work. Jaanus Liigand received first prize in the field of natural science for his Masters thesis “Electrospray ionisation efficiency scales: mobile phase effects and transferability” on a scientific works competition by Estonian Research Council. Also our (the theses were supervised by me and Karl Kaupmees) student Piia Liigand (Burk) was nominated and awarded by Estonian Academy of Science for her work “Expanding the electrospray ionization efficiency scale in positive and negative mode ESI”.

By now all three parts of Jaanus’ thesis have been submitted for publication. The last part on pH effect was submitted only on Tuesday. Piia has also by now submitted a paper on her first task about multiply charged compounds’ ionization efficiency.

Both of the students are continuing their work as PhD students in our lab. We hope to see a lot of good science also during next four years!