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Developing tools for non-target analysis and digital archiving of organic urban water pollutants
Umeå University, Faculty of Science and Technology, Department of Chemistry.ORCID iD: 0000-0002-6368-6412
2018 (English)Doctoral thesis, comprehensive summary (Other academic)Alternative title
Utveckling av verktyg för förutsättningslös analys och digital arkivering av organiska föroreningar i avloppsslam (Swedish)
Abstract [en]

This thesis describes efforts to develop robust methods for the creation and use of digital archives of environmental samples, and proposes guidelines based on the results. Digital archives are repositories that store environmental samples digitally. Traditionally, samples are stored physically in environmental specimen banks over long time periods. However, this has several drawbacks, for example degradation effects and limited accessibility. During the course of my PhD project I developed methods that allow the comprehensive analysis of sewage sludge samples. Sewage sludge is a complex matrix that contains many commercial chemicals. In addition, sewage treatment plants form a link between the human society that generates the sewage and the environment, making sewage sludge a very interesting matrix to analyze. The developed methods enable analysis and subsequent identification of compounds of all sizes and with diverse chemical characteristics. I further explain how unknown compounds can be identified (non-target screening) using mass spectral analysis and several other approaches (e.g. retention indices).

The thesis is divided into three parts. In the first part, Data Generation, I describe the development of sample preparation methods for analyzing sewage sludge with gas chromatography (GC) and liquid chromatography (LC) coupled to high resolution mass spectrometry (HRMS). For the GC approach, two methods involving use of different extraction techniques, solvents, and matrix reduction techniques are presented while for the LC approach different extraction techniques are compared. The methods have been developed to enable the generation of data suitable for digital archiving. In the second part of the thesis, Data Evaluation, I present ways to find and identify compounds of interest. Firstly, time trend analyses provide a way to prioritize pollutants, for example by focusing on pollutants that are increasing with time. Thousands of compounds with significant time trends were detected and several hundred of them were tentatively identified. Compounds with strong increasing trends included, for example, UV-filters from sunscreens. Secondly, a new retention index system for comprehensive two‑dimensional chromatography (GC×GC) is introduced to characterize compounds in terms of their retention times in the second dimension. The new retention index system is based on co-injection of polyethylene glycols and was validated for various compounds of diverse classes. Thirdly, I tested different ways to predict GC×GC retention times or indices. Those methods include a multivariate prediction (PLS) approach using molecular descriptors, which proved to be the best approach, and use of commercially available software. The last part of my thesis, Data Archiving, discusses requirements to create digital archives and how they can be used. Here I present the current state and options for archiving data files, and give recommendations for each step, from sample collection, through instrumental analysis to storage of the final data.

Abstract [sv]

I denna avhandling beskrivs innovativa metoder för att skapa och använda digitala arkiv för miljörelaterade prover, såsom biologisk vävnad, sediment och rötslam. Digitala arkiv skiljer sig från traditionella miljöprovbanker genom att resultat från analys av miljöprover fryses digitalt, istället för att fysiska prover placeras i frys. För att testa detta nya koncept utvecklades nya metoder för omfattande kemisk analys av slam från avloppsreningsverk. Avloppsslam är spännande för att det kan ge en integrerad bild av vilka kemikalier som används i samhället. Det används också för gödsling av åkermark vilket kan leda till exponering av olika organismer, inklusive människa.

De nyutvecklade metoderna möjliggör analys och efterföljande identifiering av miljöföreningar med vitt skilda kemiska egenskaper. De inkluderar icke-specifik provberedning och omfattande analys av avloppsslam med gaskromatografi (GC) respektive vätskekromatografi (LC) kopplat till högupplösande masspektrometri. För beredning av prover för GC-analys utvecklades två olika metoder för extraktion av föroreningar och eliminering av potentiellt störande ämnen, exempelvis fett och humus. Likaså optimerades extraktionstekniker för LC-analys. Genom att komplettera de båda metoderna för GC-analys med en för LC-analys kan miljöföroreningar med varierande stabilitet, storlek och polaritet analyseras. Det utvecklades även ett robust retentionindexsystem för tvådimensionell gaskromatografi (GC×GC) baserat på relativ retention i förhållande till polyetylenglykoler, liksom metoder för att beräkna retentionstider och index. Bäst resultat uppnåddes med en multivariat prediktion med hjälp av molekylära deskriptorer. Tillsammans underlättar dessa verktyg identifiering av nya potentiella miljögifter.

Analys av tidstrender användes för att prioritera bland detekterade föroreningar, till exempel för att finna föroreningar som ökar i halt med tiden. Tusentals föroreningar med statistiskt säker-ställda tidstrender upptäcktes och flera hundra av dem kunde ges en preliminär identitet. Föroreningar med starkt ökande trender inkluderade exempelvis kemikalier med UV‑blockerande egenskaper som används i solskyddsmedel.

Slutligen presenteras nuvarande status och utsikter för framtida användning av digitala arkiv. Lämpliga rutiner för digital arkivering diskuteras och det ges rekommendationer för varje steg, från insamling av prover, genom instrumentanalys till lagring av slutdata. Förhoppningen är att digitala arkiv framöver helt eller delvis kan ersätta miljöprovbanker och därmed undvika problem såsom begränsad tillgång till material, nedbrytning eller kontamination under lagring.

Place, publisher, year, edition, pages
Umeå: Umeå universitet , 2018. , p. 100
Keyword [en]
Digital archiving, non-target screening, organic pollutants, sewage sludge, GC-MS, GC×GC, LC-MS, time-trend analysis, retention indices, retention time prediction
National Category
Analytical Chemistry Environmental Sciences
Identifiers
URN: urn:nbn:se:umu:diva-144549ISBN: 978-91-7601-840-8 (print)OAI: oai:DiVA.org:umu-144549DiVA, id: diva2:1180640
Public defence
2018-03-02, KB.E3.03 (Stora hörsalen, Carl Kempe-salen), KBC-huset, Umeå, 10:00 (English)
Opponent
Supervisors
Available from: 2018-02-09 Created: 2018-02-06 Last updated: 2018-02-14Bibliographically approved
List of papers
1. Methodology for non-target screening of sewage sludge using comprehensive two-dimensional gas chromatography coupled to high-resolution mass spectrometry
Open this publication in new window or tab >>Methodology for non-target screening of sewage sludge using comprehensive two-dimensional gas chromatography coupled to high-resolution mass spectrometry
2017 (English)In: Analytical and Bioanalytical Chemistry, ISSN 1618-2642, E-ISSN 1618-2650, Vol. 409, no 20, p. 4867-4883Article in journal (Refereed) Published
Abstract [en]

To investigate the wide range of pollutants occurring in sewage sludge, an analytical method for comprehensive nontarget screening is needed. To the best of our knowledge, no procedures currently exist for the full screening of organic contaminants in sewage sludge, which is the ultimate goal of this project. We developed non-discriminating sample preparation methods for gas chromatography-mass spectrometry (GC-MS) analysis. Pressurized liquid extraction (PLE) was used for extraction, with in-line (silica gel selective PLE, SPLE) or off-line clean-up (gel permeation chromatography, GPC). This combination allowed the analysis of non-polar compounds of all sizes and small semi-polar and non-polar compounds. The results show that the combination of SPLE and PLE with GPC is suitable for analysis of established as well as new contaminants. Both methods were validated for 99 compounds with different properties. For all GC suitable analytes, either one of the methods produced acceptable recoveries (64 to 136%). As a test, the two methods were used for non-target screening of Swedish sewage sludge. A tiered approach was used to tentatively identify the sludge contaminants. In total, 1865 and 1593 compounds were found of which 321 and 192 compounds were tentatively identified for the PLE and SPLE method, respectively. For a comprehensive coverage of contaminants, the two methods should be used together, with the PLE method covering a wider polarity range and the SPLE method a wider size range. In addition, polar substances will require liquid chromatography-mass spectrometry analysis, the method for which will be developed soon.

Place, publisher, year, edition, pages
Springer, 2017
Keyword
Non-target screening, Sewage sludge, Method development, GC-HRMS, GC x GC
National Category
Analytical Chemistry
Identifiers
urn:nbn:se:umu:diva-138204 (URN)10.1007/s00216-017-0429-0 (DOI)000406146800018 ()28646300 (PubMedID)
Available from: 2017-08-21 Created: 2017-08-21 Last updated: 2018-02-06Bibliographically approved
2. Non-target screening and time trend analysis of sewage sludge contaminants via comprehensive two-dimensional gas chromatography
Open this publication in new window or tab >>Non-target screening and time trend analysis of sewage sludge contaminants via comprehensive two-dimensional gas chromatography
(English)Manuscript (preprint) (Other academic)
Keyword
Gas chromatography, GC×GC, non-target screening, time-trend analysis, sewage sludge, data reduction
National Category
Environmental Sciences
Identifiers
urn:nbn:se:umu:diva-144542 (URN)
Available from: 2018-02-06 Created: 2018-02-06 Last updated: 2018-02-06
3. A retention index system for comprehensive two-dimensional gas chromatography using polyethylene glycols
Open this publication in new window or tab >>A retention index system for comprehensive two-dimensional gas chromatography using polyethylene glycols
2018 (English)In: Journal of Chromatography A, ISSN 0021-9673, E-ISSN 1873-3778, Vol. 1536, p. 67-74Article in journal (Refereed) Published
Abstract [en]

The characterization and identification of compounds in complex real-world samples is quite difficult and new concepts and workflows are highly desirable. Retention indices (RIs) are widely used in gas chromatography (GC) to support the identification of unknown compounds. Several attempts have been made to introduce a similar concept for the second dimension in comprehensive two-dimensional (2D) GC (GC × GC) but, an easily applicable and robust system remains elusive. In the present study, a new RI system for GC × GC was developed. Polyethylene glycols (PEGs) were used in combination with a simple linear regression, with n-alkanes as reference points for virtually unretained compounds and PEG homologs as reference compounds for second-dimension RIs (PEG-2I). The n-alkanes were assigned a PEG-2I of zero and the distance between consecutive PEG homologs from PEG-2 (diethylene glycol) and higher were assigned a PEG-2I value of 10. We used ethylene glycol and PEG-2 through PEG-10 as reference compounds, thereby covering a PEG-2I range from 20.0 for ethylene glycol, over 50.0 for diethylene glycol (PEG-2) to 130.0 for decaethylene glycol (PEG-10); additional PEGs can be added to cover a wider polarity range. The PEG-2I system was initially evaluated using a 30 m × 0.25 mm non-polar (5% phenyl, 0.25 μm film thickness) first-dimension column and a 1.6 m × 0.18 mm polar (50% phenyl, 0.18 μm film thickness) second-dimension column. This system was validated for use with non-polar first-dimension columns and a semi-polar (50% phenyl) second-dimension column, and exhibited robustness to changes in the carrier gas flow velocity, oven temperature ramping rate, and secondary oven temperature offset. An average relative standard deviation of 2.7%, equal to a 95% confidence interval of 1.27 PEG-2I units, was obtained for the PEG-2I values of 72 environmental pollutants. Additionally, the system was found to be applicable over a wide range of boiling points (in the current case, from n-heptane to n-dotriacontane (C7-C32)) and can be used with various column dimensions. Changing the second-dimension column to either a narrower 0.1 mm column or a wider 0.25 mm column, yielded similar 95%-percentiles to that of the 0.18 mm column, differing by only 3.20 and 2.80 PEG-2I units, respectively. Moreover, methods for improving the system were suggested.

Keyword
GC×GC, Retention indices, Polyethylene glycols, n-alkanes, Environmental contaminants
National Category
Analytical Chemistry
Identifiers
urn:nbn:se:umu:diva-144541 (URN)10.1016/j.chroma.2017.08.062 (DOI)000425074200009 ()28882343 (PubMedID)
Available from: 2018-02-06 Created: 2018-02-06 Last updated: 2018-04-18Bibliographically approved
4. Retention time prediction in comprehensive two-dimensional gas chromatography to aid identification of unknown contaminants
Open this publication in new window or tab >>Retention time prediction in comprehensive two-dimensional gas chromatography to aid identification of unknown contaminants
(English)Manuscript (preprint) (Other academic)
Keyword
GC×GC, retention-time prediction, partial least squares (PLS), federation of local models, quantitative structure–retention relationship (QSRR)
National Category
Analytical Chemistry
Identifiers
urn:nbn:se:umu:diva-144544 (URN)
Available from: 2018-02-06 Created: 2018-02-06 Last updated: 2018-02-06

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