A number of performance characteristics were evaluated including drift, intermediate precision, accuracy of temperature compensation, accuracy of reading (under different measurement conditions), linearity, flow dependence of the reading, repeatability (reading stability), and matrix effects of dissolved salts. The matrix effects on readings in real samples were evaluated by analyzing the dependence of the reading on salt concentration (at saturation concentration of DO). The analyzers were also assessed in DO measurements of a number of natural waters. The uncertainty contributions of the main influencing parameters were estimated under different experimental conditions. It was found that the uncertainties of results for both analyzers are quite similar but the contributions of the uncertainty sources are different.
The results imply that the optical analyzer might not be as robust as is commonly assumed, however, it has better reading stability, lower stirring speed dependence, and typically requires less maintenance. On the other hand, the amperometric analyzer has a faster response and wider linear range.
(Photo by Lauri Jalukse: measurements of dissolved oxygen concentration with amperometric and optical analyzers at Jordan spring, Karksi-Nuia, Estonia)
On May 14, 2018 the on-line course (MOOC) Estimation of measurement uncertainty in chemical analysis offered by University of Tartu finished successfully.
Eventually altogether 521 people registered (270 in 2014, 489 in 2015, 757 in 2016, 363 in 2017) from 76 countries (a number of participants joined after the start of the course). 358 participants actually started the course (i.e. tried at least one graded test at least once) and out of them 218 successfully completed the course (141 in 2014, 169 in 2015, 308 in 2016, 148 in 2017). The overall completion rate was 42% (52% in 2014, 34% in 2015, 40% in 2016, 41% in 2017). The completion rate of participants who started the studies was 61% (67% in 2014, 60% in 2015, 67% in 2016, 68% in 2017). The completion rates are nicely consistent over the last 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. The questions 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 almost 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 of 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 2019.
Traditional analytical chemistry group seminar was this time held in beautiful Voore Guest House on 5-6th of May. Despite the sunny and wonderful weather outside, a group of analytical chemists were pleased to stay inside to discuss research. Since many of our group members are going to defend their theses soon (PhD students Märt Lõkov and Sofja Tšepelevitš, master’s students Alo Rüütel and Andre Leesment, and bachelor’s students Elisabeth Parman and Lisett Kiudorv), their presentations were followed by many questions and fruitful discussions. Another PhD student, Max Hecht, joined us via Skype and gave us an interesting presentation about sponge spray while reminding that every chemist must face many problems and difficulties before gaining the expected results. Besides numerous analytical chemistry research-related presentations, our research fellow Dr. Riin Rebane, who is currently studying law, introduced us a world of law and talked about patent applications in Estonia. The whole seminar was finished with a gripping presentation about postdoctoral studies in the University of Helsinki by Dr. Hanno Evard.
In addition to the intense seminar, we were able to enjoy the beautiful nature and landscape of Vooremaa while taking a long walk in the village and discussing the day’s events in a hot sauna.
Sum of pesticide traces in samples from 2016-2017. Source: Estonian Environmental Research Centre
Our joint research fellow with Estonian Environmental Research Centre Dr. Riin Rebane and joint PhD candidate Siiri Saaver participated in the study “Analysis of pesticide traces and dynamics in surface and groundwater” . In this study, 137 surface and groundwater samples from all over Estonia were analysed with a targeted screening of 135 pesticides. From 137 analysed samples 49 pesticide traces were detected in more than half of the samples. In 34 samples 9 pesticides and their metabolites exceeded the allowed concentration level of 0.1 μg/L. In 9 samples pesticides and their transformation products exceeded 0.5 μg/L. Interestingly, the main compound found (in 26 samples) was chloridazon-desphenyl, which is a metabolite of pesticide chloridazon that is not registered on Estonian market and therefore not sold, which makes the determination of the origin of this compound complicated. It needs further research whether it is a remnant of Soviet times and slowly moving in the soil towards groundwater or if it is in use now.
This study was also reported in news portal Novaator and in environmental TV show Osoon
Moreover, there are hundreds of different pesticides and targeted screening methods usually look for compounds that are banned or known to be problematic. This study used the broader list of pesticides than regular yearly monitoring of pesticides indicating that broader coverage of potential pollutants is needed. Therefore, there is a need for the suspect and non-target screening methods for detecting more compounds and their metabolites.
In collaboration with Estonian Environmental Research Centre, our group has also contributed to studying and developing the non-target approach. Namely, Gunnar Printsmann developed in his master thesis suspect and non-target screening method for groundwater using high-resolution mass spectrometry which also included pollutants database. He found and confirmed a new industrial pollutant dibutyl phthalate in one sample from North-Eastern Estonia.
Our PhD student Jaanus is currently doing research in the group of Prof. Edwin De Pauw at the University of Liege in Belgium and he had a nice opportunity to take part in a 21st annual meeting of Belgian Society for Mass Spectrometry that was held on 29th of March in Liege. The meeting was organized in honour of Prof. Edwin De Pauw to summarize his work as he intended to retire after this year. Luckily for the mass spectrometric community, he will be actively involved in the research at least for four coming years.
Prof. Scott McLuckey opened the day with a presentation about strategies for achieving enzyme-like specificity in the gas-phase fragmentation of peptide and proteins. He showed different strategies how to cleave for example specifically at asparagine or lysine.
Prof. Andrea Sinz presented the results of the development of cleavable cross-linkers. Additionally, she pointed out that although cleavable crosslinkers are available on the market most of the groups determining the protein structures still use the noncleavable crosslinkers and do not take advantage of additional information provided by cleavable crosslinkers.
Dr. Valérie Gabelica presented the results of the studies of nucleic acid noncovalent complexes in native MS. She said that by knowing and studying the fundamentals of ESI processes one gets also a real insight into phenomena seen in different applications (in her case, nucleic acid noncovalent complexes). She also pointed out that unfortunately, scientific community publishes solely positive results which result in biased and non-universal theories.
Jaanus Liigand also had the possibility to present the results of our studies of standard substance free quantitation in LC/ESI/MS analysis and industry showed a great interest in our approach which could be beneficial for their needs (see the poster here).
It was a really nice day full of interesting presentations and discussions.
The aim of the conference was to bring together chemists, physicists, geologists, art historians, conservators, archaeologists, etc. to create a wide community and a mutual environment for a fruitful discussion. Four days were filled with wide-ranging presentations, museum visits and interesting discussions with other scientist from the same scientific fields. The work of our cultural heritage group was also introduced with both oral and poster presentations.
On the left picture you can see Eliise standing next to her poster about the comparison of derivatization methods for GC-MS analysis of binding materials in oil paints. The results of this work are going to be published soon.
On the right picture is Pilleriin presenting her work on textile dye analysis. This work has already been submitted.
Every year Estonian University of Life Sciences organises a conference called “Healthy animal and healthy food” where Dr. Riin Rebane made a presentation “Fight against food fraud” which explained the ever-expanding role of analytical chemists in food science. Reasons for food fraud vary, but are almost always for monetary gain and therefore food fraud is in constant progress. One good example is honey analysis, where for decades there has been a change in methods in order to identify whether honey is real or whether it is identified with correct botanical or geographical origin. As a natural product, no two honeys are identical and this makes identification further more challenging for the chemists. One of the possible methods is amino acid analysis since the amino acid content can be like a fingerprint for honeys and in University of Tartu we have analysed few hundreds of Estonian honeys and have seen that that foreign honeys do differ in most cases and also that there is a correlation between the amino acid content and botanical origin. But nevertheless, even this method might not work every time and chemists are looking towards methods such as nuclear magnetic resonance spectroscopy and even DNA-analysis to get better certainty for determining the origin of honey.
The summary based on the presentation was also reported in the newspaper Maaleht.
Dr. Anneli Kruve, a leader of research team focussing on ionization efficiency studies in electrospray, is currently a Humboldt fellow in Freie Universität Berlin and visited the 1st European Mass Spectrometry Conference in Saarbrücken (Germany) this month. She describes some of the highlights of this conference in her blog, you can read the post below.
Last week I had a chance to take part in the European Mass Spectrometry Conference that was hosted by DGMS (German Society for Mass Spectrometry) and SFSM (French Society for Mass Spectrometry). Below I share a few key ideas from this nice conference that took place in Saarbrücken over 5 days.
The conference was opened with a plenary lecture by Prof. Alain van Dorsselaer who summarized the main work he and his group has done on mass spec during the last 30 years. One of the key ideas, that came up several times in his talk referred to the fact that endless possibilities are accompanied by extreme data load. The amount of data in LC/MS/MS is huge and it is very complicated to analyse these massive data sets. Several other scientists, including Prof. Andreas Roempp and his group, also stressed the importance of transparent and open source data analyses and storage that could eventually simplify the data treatment. These ideas strongly resonate with my own ideas of applying more data science tools in primary data treatment in mass spectrometry, as today the data processing is by far limiting the progress in several fields of analytical mass spectrometry. Mostly this is the case for fields, where the science is still in the “discovery” stage; meaning that the scientists aim at finding the important compounds and yet do not know which these compounds could be. Such fields include metabolomics, proteomics, environmental science, etc.
Prof. Philippe Schmitt Kopplin stressed the importance of high throughput in metabolic sample analyses and explained why dissolve-and-shoot approach (flow-injection or infusion combined with MS) is often most practical. Also, he showed several case studies where marker compounds could be reliably identified with this simple approach if accompanied with efficient and accurate data processing. A particularly interesting example was a case study of 170-year-old wine from the bottom of the Baltic Sea.
Prof. Carsten Engelhard showed an extremely clever, almost brilliant, method to analyse nanoparticles with simple dilution & infusion experiment. The infusion of homogeneous solution to ICP-MS instrument causes an almost constant signal with small random variations. However, if the solution of nanoparticles is infused to ICP-MS, most of the time there is no signal (only noise). When one of the nanoparticles enters the plasma a signal suddenly occurs causing a peak in the chronogram. The height of the signal reflects the size of the nanoparticle and the number of peaks per volume indicates the concentration of the nanoparticles.
Prof. Thomas Kraemer introduced us to the world of forensic analyses. Particularly, he focused on MALDI imaging techniques, that allow revealing drug intake or exposure to toxic compounds. For this purpose his lab is using two types of samples, the traditional hair and lately also toenails, to overcome the problem arising for hairless people. Interestingly, the single hair analysis also reveals time-resolved information with high precision; therefore, allowing to distinguish between one-time and long time exposures.
You can check out more posts from our team studying ionization efficiencies kruvelab.com
Currently, more than 450 participants from 70 countries are registered! As was the case in the previous years, the majority of participants are from analytical laboratories. This once again demonstrates the continuing need for training in measurement uncertainty estimation for practising analytical chemists.
The full course material is accessible from the web page https://sisu.ut.ee/measurement/uncertainty. As is usual, some developments and improvements have been made to the course material. in particular, the description of course organisation was improved; more explanations and examples were added on random and systematic effects within short and long-term; the typical requirements for determining repeatability and within-lab reproducibility have been clearly outlined; more explanations on the main principles of modifying a model in a modelling approach have been given, together with an example. 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 pass six graded tests and get higher than 50% score from each of them. These tests are available to registered participants via the Moodle e-learning platform.
We currently have more than 100 registered participants from more than 30 countries.
The full course material (as well as the registration link) is accessible from the web page https://sisu.ut.ee/measurement/uncertainty. 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. Participants who successfully pass the course will get a certificate from University of Tartu. A digital certificate of completion is free of charge. A certificate of completion on paper can be requested for a fee of 60 euros.
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A comprehensive comparative validation for two different types of dissolved oxygen (DO) analyzers, amperometric and optical, together with estimation of measurement uncertainty is presented in the recently published article I. Helm, G. Karina, L. Jalukse, T. Pagano, I. Leito, Environmental Monitoring and Assessment 2018, 190, 313.
