Applicability of comprehensive two-dimensional gas chromatography : time-of-flight mass spectrometry to environmental non-target screening : Special emphasis on wastewater

The flux of emerging organic contaminants into environment is a global threat, which is widely studied and monitored. However, current regulation is not able to keep up with the increasing variety of new compounds released to the environment. More efficient and comprehensive analytical methodologies are required to enable sufficient monitoring of these compounds for legislative purposes. Non-targeted analytical approaches are able to identify previously unknown contaminants, which is not possible with conventional targeted methods. Therefore, the development of novel non-target methodologies is important. The goal of the thesis was to look for new ways to utilize non-targeted data for environmental applications with a special emphasis on wastewater analysis. The developed methodologies focused on chemometric quantification of non-target compounds, identification of steroidal transformation products, statistical cross-sample analysis of wastewater and atmospheric particles as well as non-targeted approaches to quantify selectivity of adsorbents employed in sample preparation. The samples were analyzed by comprehensive two-dimensional gas chromatography ‒ time-of-flight mass spectrometry utilizing mass spectral libraries and retention indices for compound identification. Different solid-phase extraction procedures were applied to aqueous samples, and ultra-sound assisted extraction to solid samples. The study included also the synthesis of novel polymeric adsorbents with increased selectivity towards steroidal compounds. Modern statistical software was utilized for data handling and chemometrics. The multidimensional system enabled the analysis of complex wastewater samples, and several steroids and their transformation products were identified from the samples. It was concluded that hydrophobic steroids were efficiently removed from wastewater by adsorption to sewage sludge. However, elimination from sludge was less efficient and steroids were also found in the processed sludge destined for agricultural purposes. The chemometric model for the prediction of concentrations of non-target compounds with steroidal structure demonstrated good accuracy. Non-targeted approaches allowed the arithmetic comparison of adsorbent selectivity, when previously only relative methods have been used. Fast comparison of different wastewater and aerosol samples was possible through cross-sample analysis with non-targeted data. Non-targeted approaches presented in this thesis can also be applied to other groups of contaminants and thus promote the available knowledge about environmental pollution. New ways to utilize non-targeted methodologies and cross-sample analyses demonstrated their value in this thesis and hopefully inspire future studies in the field.Orgaanisten haitta-aineiden kerääntyminen ympäristöön on laajalti tutkittu globaali ongelma. Näiden yhdisteiden seuraaminen ja sääntely on kuitenkin hankalaa, koska lainsäädäntö on hitaampaa kuin uusien kemikaalien kehittäminen. Tämän takia tarvitaan tehokkaampia ja laaja-alaisempia analyysimenetelmiä, jotta uudet vesistöihin päätyvät haitta-aineet voidaan havaita mahdollisimman nopeasti. Perinteisillä menetelmillä voidaan tutkia vain tunnettuja yhdisteitä, koska näytteessä olevat yhdisteet tunnistetaan vertaamalla niiden retentioaikoja ja massaspektrejä puhdasaineisiin. Non-target -analyysi sen sijaan ei vaadi tarkkoja ennakkotietoja yhdisteistä ja sillä voidaan havaita myös ennestään tuntemattomia haitta-aineita. Tämän väitöskirjan tavoitteena oli kartoittaa uusia tapoja hyödyntää non-target -analytiikkaa ympäristötutkimukseen ja etenkin jätevesinäytteisiin. Tärkeimpiä sovelluksia olivat tuntemattomien yhdisteiden pitoisuuksien määrittäminen kemometrisesti, steroidien muuntautumistuotteiden tunnistaminen, tilastollinen jätevesi- ja aerosolinäytteiden vertailu sekä näytteen esikäsittelyyn tarkoitettujen adsorbenttien selektiivisyyden mittaaminen. Näytteet analysoitiin laajalla monivaiheisella kaasukromatografialla liitettynä lentoaika massaspektrometriaan ja yhdisteet tunnistettiin hyödyntäen spektrikirjastoja ja retentioindeksejä. Nestemäisten näytteiden esikäsittelyyn käytettiin erilaisia kiinteäfaasiuutto-tekniikoita ja kiinteiden näytteiden käsittelyyn käytettiin ultraääniuuttoa. Tutkimuksessa myös syntetisoitiin uusia adsorbenttipolymeerejä steroidien selektiivistä uuttoa varten. Monivaiheisella kromatografialla analysoitiin monimutkaisia jätevesinäytteitä, joista tunnistettiin luotettavasti useita steroideja sekä niiden muuntautumistuotteita. Havaittiin, että hydrofobiset steroidit poistuvat jätevedestä tehokkaasti adsorboitumalla lietteeseen. Lietteessä yhdisteet olivat pysyvämpiä ja steroideja havaittiin jopa kompostoidussa lietteessä, jota myydään puutarhamullaksi. Kemometrisen mallinnuksen avulla pystyttiin ennustamaan entuudestaan tuntemattomien yhdisteiden pitoisuuksia massaspektrien avulla hyvällä tarkkuudella. Non-target -menetelmällä onnistuttiin vertailemaan numeerisesti eri adsorbenttien selektiivisyyttä steroideja kohtaan. Non-target -analyysi mahdollisti myös useiden jätevesi- ja aerosolinäytteiden nopean vertailun käyttämällä hyväksi koko näytteestä saatavaa tietoa. Tässä väitöskirjassa esiteltyjä non-target -menetelmiä voidaan helposti soveltaa myös muille yhdisteryhmille ja näin nopeuttaa ympäristönäytteiden analyysiä ja uusien haitta-aineiden tunnistamista. Työssä käytetyt sovellukset havainnollistavat non-target -analytiikan etuja ja motivoivat jatkotutkimuksia

Nontargeted evaluation of the fate of steroids during wastewater treatment by comprehensive two-dimensional gas chromatography-time-of-flight mass spectrometry

Emerging organic contaminants in wastewater are usually analyzed by targeted approaches, and especially estrogens have been the focus of environmental research due to their high hormonal activity. The selection of specific target compounds means, however, that most of the sample components, including transformation products and potential new contaminants, are neglected. In this study, the fate of steroidal compounds in wastewater treatment processes was evaluated by a nontargeted approach based on comprehensive two-dimensional gas chromatography-time-of-flight mass spectrometry. The potential of the nontargeted approach to generate comprehensive information about sample constituents was demonstrated with use of statistical tools. Transformation pathways of the tentatively identified compounds with steroidal four-ring structure were proposed. The purification efficiency of the wastewater treatment plants was studied, and the distribution of the compounds of interest in the suspended solids, effluent water, and sludge was measured. The results showed that, owing to strong adsorption of hydrophobic compounds onto the solid matter, the steroids were mostly bound to the suspended solids of the effluent water and the sewage sludge at the end of the treatment process. The most abundant steroid class was androstanes in the aqueous phase and cholestanes in the solid phase. 17 beta-estradiol was the most abundant estrogen in the aqueous phase, but it was only detected in the influent samples indicating efficient removal during the treatment process. In the sludge samples, however, high concentrations of an oxidation product of 17 beta-estradiol, estrone, were measured.Peer reviewe

Assessment of polar organic aerosols at a regional background site in southern Africa

A recent paper reported GCxGC-TOFMS analysis used for the first time in southern Africa to tentatively characterise and semi-quantify 1000 organic compounds in aerosols at Welgegund - a regional background atmospheric monitoring station. Ambient polar organic aerosols characterised are further explored in terms of temporal variations, as well as the influence of meteorology and sources. No distinct seasonal pattern was observed for the total number of polar organic compounds tentatively characterised and their corresponding semi-quantified concentrations (sum of the normalised response factors, Sigma NRFs). However, the total number of polar organic compounds and Sigma NRFs between late spring and early autumn seemed relatively lower compared to the period from mid-autumn to mid-winter, while there was a period during late winter and early spring with significantly lower total number of polar organic compounds and Sigma NRFs. Relatively lower total number of polar organic compounds and corresponding Sigma NRFs were associated with fresher plumes from a source region relatively close to Welgegund. Meteorological parameters indicated that wet removal during late spring to early autumn also contributed to lower total numbers of polar organics and associated Sigma NRFs. Increased anticyclonic recirculation and more pronounced inversion layers contributed to higher total numbers of polar organic species and Sigma NRFs from mid-autumn to mid-winter, while the influence of regional biomass burning during this period was also evident. The period with significantly lower total number of polar organic compounds and Sigma NRFs was attributed to fresh open biomass burning plumes occurring within proximity of Welgegund, consisting mainly of volatile organic compounds and non-polar hydrocarbons. Multiple linear regression substantiated that the temporal variations in polar organic compounds were related to a combination of the factors investigated in this study.Peer reviewe

Characterising Particulate Organic Nitrogen at A Savannah-Grassland Region in South Africa

Although atmospheric organic N compounds are considered to be important, especially in new particle formation and their contribution to brown carbon, these species are not that well understood. This can be partially attributed to their chemical complexity. Therefore, the aim of this study was to assess the characteristics of organic N compounds utilising comprehensive two-dimensional gas chromatography coupled with a time-of-flight mass spectrometer (GCxGC-TOFMS) in aerosol samples that were collected at a savanna-grassland background region and to determine the possible sources. 135 atmospheric organic N compounds were tentatively characterised and semi-quantified, which included amines, nitriles, amides, urea, pyridine derivatives, amino acids, nitro-and nitroso compounds, imines, cyanates and isocyanates, and azo compounds. Amines contributed to 51% of the semi-quantified concentrations, while nitriles, pyridine derivatives, and amides comprised 20%, 11%, and 8%, respectively, of the semi-quantified concentrations. Amines, nitriles, amides, and pyridine derivatives concentrations were higher during the dry season, which were attributed to meteorology and open biomass burning. Anthropogenic sources impacting air masses measured at Welgegund, as well as regional agricultural activities, were considered as the major sources of amines, while the regional influence of household combustion was most likely the main source of nitriles, amides, and pyridine derivatives. The other organic N species were most likely related to the influence of local and regional agricultural activities.Peer reviewe