Browsing by Subject "Master's Programme in Chemistry and Molecular Sciences"

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  • Suuronen, Markus (Helsingin yliopisto, 2021)
    People spend more than 90% of time indoors. That has made the analysis of indoor air quality an subject of interest. There is a growing popularity of miniaturized sample extraction techniques utilizing solid adsorbent materials and thermal desorption allowing direct sample introduction for analysis. This approach is solvent free and there is possibility for reusing adsorbent materials depending of adsorbent properties. This thesis covers the basics of adsorption-desorption process and takes detailed look on different adsorbent materials such as activated carbon (AC), metal-organic framework (MOF) and carbon nanotubes (CNT) and evaluates the effect of surface functionality and pore size distribution for adsorption process. In experimental part, a self-made autosampler functionality and its injection parameters were optimized. The autosampler is able to independently inject up to six in-tube extraction (ITEX) needles with complete desorption. The ITEX was constructed during this experiment with TENAX-GR adsorbent and the repeatability of autosampler and ITEXs were tested and compared to commercial system with extraction of different amines. The effectiveness of this system was also demonstrated for indoor volatile organic compound (VOC) analysis.
  • Sachan, Sinivuokko (Helsingin yliopisto, 2021)
    At low concentrations, biogenic amines (BA) promote natural physiological activity, but at higher concentrations they can cause a wide variety of health hazards, especially for more sensitive individuals. The BA determination in wine is challenging due to the variation in physicochemical properties and the potential matrix effects of other compounds in the sample. It is important to develop efficient sample purification methods to minimize matrix interference. Derivatization is required for most biogenic amines due to the absence of chromophores. The conditions that promote the origin or formation of biogenic amines in wines are not yet fully understood, as many factors contribute to their formation. The main sources or stages of BA formation during wine-making should be identified in order to reduce BA levels by corrective measures. Currently, the analytical community is striving for more environmentally friendly methods. The literature review examines methods for determination of biogenic amines in wines from 2005 until 2020. The methods are high-performance liquid chromatography, ultra-high-performance liquid chromatography, high-temperature liquid chromatography, nano-liquid chromatography, micellar liquid chromatography, capillary electrophoresis, micromachined capillary electrophoresis, gas chromatography, immunoassay, sensor, colorimetric method, thin-layer chromatography and ion chromatography. The health disadvantages of biogenic amines and the problem areas associated with their determination from a complex wine matrix, such as matrix effect and derivatization, are also surveyed. In addition, changes in the BA profile during different stages of winemaking and storage, as well as the effect of the grape variety and lactic acid bacterial strain on the BA profile, are surveyed. Validation determines the suitability of a method for its intended use. In the methods for determining the literature review, measurement uncertainty - possibly the most important validation parameter - had not been determined in any of the validations. The aim of the research project was to obtain a functional and validated method for the determination of biogenic amines in wines for the Alcohol Control Laboratory at Alko Inc. In the method tested, histamine, tyramine, putrescine, cadaverine, phenylethylamine and isoamylamine derivatized with diethyl ethoxymethylene malonate were determined by high-performance liquid chromatography and diode array detector. The method was not sufficiently reliable, so a competitive enzyme-linked immunosorbent assay for the determination of histamine in wines was introduced, which provided a useful method for the Alcohol Control Laboratory. The validation determined specificity/selectivity, recovery, repeatability, systematic error, estimation of random error, measurement uncertainty, expanded measurement uncertainty, limit of detection and limit of quantification. The European Food Safety Authority has confirmed histamine and tyramine as the most toxic amines. The International Organization of Vine and Wine has not set legal limits for BA levels, but some European countries have had recommended maximum levels for histamine. Many wine importers in the European Union require a BA analysis even in the absence of regulations. Based on the literature review, high BA levels were found in the wines under study, including levels of histamine, tyramine, and phenylethylamine that exceeded the toxicity limits. Some wines had biogenic amines below the detection limit, so the production of low-amine wines is possible. In addition, certain strains of lactic acid bacteria were found to significantly reduce the BA levels in wine. High-performance liquid chromatography is the most widely used determination method. An increasing trend is to develop simpler methods such as the portable sensor-based method.
  • Elliott, Todd (Helsingin yliopisto, 2019)
    An investigation into switchable polarity ionic liquids was carried out to find greener alternative substituents and still obtain a switchable polarity ionic liquid. First for fluorinated compounds (fluorinated alcohol and amine) with a non-fluorinated hydroxylamine to form a mixed carbamate, then replacing the superbase with a basic tertiary (or secondary) amine. The trigger molecule for switching polarity was CO2. It was found that O-hexylhydroxylamine was a suitable replacement for fluorinated ethanol and fluorinated ethylamine to work with DBU (superbase) to form a switchable polarity ionic liquid. The three amines of triethylamine (TEA), diisopropylethylamine (Hünigs base) and diisopropylamine (DIPA) were inconclusive or unsuccessful. Both TEA and DIPA require further alternative analysis for a conclusive result while Hünigs base was proven to be unsuccessful. These reaction products were characterised with 1H and 13C NMR and ReactIR spectral data. Synthesis of hydroxylamine was also approached for a greener improvement. A new synthesis method is demonstrated that is successful using water and methylamine in ethanol working on reaction equilibria. The new method proposed had a yield of 29.1%, while the patent literature method that used hydrazine monohydrate (which is highly toxic and unstable unless in solution) gave a yield of 54.3% of hydroxylamine. A secondary investigation was also undertaken in to basicity effects of caesium carbonate on the CO2 addition to aniline, with and without a superbase present. The superbase used was tertramethylguanidine (TMG). Aniline, p-nitroaniline and p-methoxyaniline were tested for CO2 addition by formation of an amide peak in ReactIR. There was formation of the amide peak with caesium carbonate, though not as much as with the already known TMG. A concentration series of caesium carbonate and TMG in aniline was also devised to observe the effect the added caesium carbonate had on the aniline-TMG system in absorbing CO2. This was also analysed using ReactIR spectra. It was seen generally that by increasing the concentration of both/either TMG/Cs2CO3 there is an increase in carbamate. However further concentration series data is required before a generalised rule can be defined.
  • Meriläinen, Veronika (Helsingin yliopisto, 2022)
    As nuclear reactors come to the end of their lifetime, they undergo decommissioning. All the construction materials and spend nuclear fuel must be characterized according to their activities before final disposal. For the analysis of difficult to measure radionuclides, such as beta emitters, sample decomposition methods are used. Acid digestion, alkaline fusion and thermal combustion are examples of sample decomposition methods. In this work, alkaline fusion methods were tested to gain knowledge on the suitability of the method for volatile and non-volatile radionuclides in decommissioning waste. The sample materials tested were concrete and two difficult to dissolve reference materials: soil and coal fly ash. Results obtained with alkaline fusion were compared with that of routinely used acid digestion method. In addition, activated graphite was studied to familiarize with the analysis of difficult to measure radionuclides. Non-volatile 63Ni and 55Fe and volatile 3H and 14C were studied. The results were compared with modelled activities. Alkaline fusions were performed with a borate flux in an automated fusion oven as well as with a carbonate flux in a muffle furnace. Acid digestion was performed in an open vessel with aqua regia. The dissolved samples were analysed with ICP-OES and ICP-MS for determination of elemental concentrations. Borate fusion seemed to be the most effective method, as it was suitable for all the sample materials and released even refractory elements. Some of the volatile elements were lost during the fusion methods (Cd and Zn), while some were not affected by the high temperatures used (Pb). Alkaline fusion methods appeared to be suitable for decommissioning studies, however further research is needed. In analysis of graphite, non-volatile elements were analysed by acid digestion. 55Fe and 63Ni were separated from the matrix by hydroxide precipitation and from each other by ion exchange in an AG-resin. Ni fraction was further purified by extraction chromatography with a Ni-resin. Volatile elements were analysed by thermal combustion in a pyrolyser. The activities of 55Fe, 63Ni, 3H and 14C were measured with liquid scintillation counting. The measured activity concentrations of 63Ni were partially in agreement with the modelled values, but some samples gave higher activities. No 55Fe activities were found in any samples, as was expected based on the modelled values and the short half-life of the radionuclide. Activities of the volatile 3H and 14C were accurate and close to the modelled values. In the future, the determined activity results will be used for improving scaling factors, for the assessment of radionuclide concentrations in graphite.
  • Heiskanen, Ilmari (Helsingin yliopisto, 2021)
    Interest towards indoor air quality has increased for several decades from human health perspective. In order to evaluate the quality of indoor air in terms of volatile organic compound (VOC) levels, robust analytical procedures and techniques must be used for indoor air VOC measurements. Since indoor building materials are the greatest source of indoor VOC emissions, same kind of procedures must be used for analysis of emission rates from building materials and their surfaces. Theory part of this thesis reviews background of VOCs and human health, legislation and guideline values, common building materials with emissions and used sampling techniques/approaches for indoor air sampling and surface material emission rate sampling & analysis. Discussed sampling techniques include, for example, material emission test chambers, field and laboratory test emission cells, solid phase microextraction (SPME) fibre applications and Radiello passive samplers. Also new innovative approaches are discussed. Used common analysis instruments are Gas Chromatography (GC) with Mass Spectrometer (MS) or Flame Ionization Detector (FID) for VOCs and High-Performance Liquid Chromatography-Ultraviolet/Visible light detector (HPLC-UV/VIS) for carbonyl VOCs (e.g. formaldehyde) after suitable derivatization. Analytical procedures remain highly ISO 16000 standard series orientated even in recent studies. In addition, potential usage of new modern miniaturized sample collection devices SPME Arrow and In-tube extraction (ITEX) used in experimental part of this thesis are discussed as an addition to indoor air and VOC emission studies. The aim of the experimental part of this thesis was to develop calibrations for selected organic nitrogen compounds with SPME Arrow and ITEX sampling techniques and test the calibration with indoor and outdoor samples. A calibration was successfully carried out with SPME Arrow (MCM-41 sorbent), ITEX (MCM-TP sorbent) and ITEX (Polyacrylonitrile (PAN) 10 % sorbent) with permeation system combined with GC-MS for the following selected organic nitrogen compounds: triethylamine, pyridine, isobutyl amine, allylamine, trimethylamine, ethylenediamine, dipropyl amine, hexylamine, 1,3-diaminopropane, 1-methyl-imidazole, N, N-dimethylformamide, 1,2-diaminocyclohexane, 1-nitropropane and formamide. The overall quality of the calibration curves was evaluated, and the calibrations were compared in terms of linear range, relative standard deviation (RSD) % for accepted calibration levels and obtained Limits of Detection (LOD) values. Also, ways to improve the calibrations were discussed. The calibration curves were tested with real indoor and outdoor samples and quantitative, as well as semi-quantitative, results were obtained.
  • Kivinen, Anssi (Helsingin yliopisto, 2020)
    The analysis of volatile organics is growing by the year and there is a great interest in fast and simple sample preparation techniques. With solid phase micro-extraction, samples can be extracted non-destructively without a need for solvents. This is both cost effective and ecological, because even most eco-friendly solvents still cause strain on the environment. This thesis focused on studying the effect of extraction conditions on the extraction efficiency. The effect of different sorptive phase materials was tested as well. New single-step sample extraction and preparation method was developed for gas chromatographic mass spectrometric analysis. Three different sorptive phase materials were compared and the extraction conditions were optimized for each. The method developed was used to extract, analyze and determine unknown compounds from a butterfly specimen. Multiple extractions were performed from both headspace and with direct immersion. By progressively changing the extraction conditions, properties of the compounds such as volatility and polarity could be determined by their presence alone. Analysis was performed using with gas chromatography mass-spectrometer using electron ionization quadrupole mass detector in full scan mode.
  • Youngren, Cristina (Helsingin yliopisto, 2023)
    Novichok nerve agents are persistent, highly toxic chemical weapons which were added to the Chemical Weapons Convention in 2020 after their use on civilians in England. The detection and characterization of Novichok nerve agents and the degradation products formed after their exposure to decontamination products can be accomplished through complementary instrumental analyses. Chromatographic methods such as LC-MS/MS can be utilized to qualitatively detect Novichok degradation products such as hydrolysates and LC-HRMS can provide information about their structure via the elemental composition and fragmentation pathways. By contrasting these data to spectroscopic techniques such as 1H and 31P NMR, structural elucidation of decontamination products is possible as well as the determination of the kinetics of the decontamination process itself. The literature review contains a summary of all published instrumental methods with which Novichok nerve agents, degradation products, biomarkers and adducts have been analyzed and the efficacy of those methods. In the experimental research, Novichok nerve agent A-234 was decontaminated via six different decontaminants and analyzed by LC-MS/MS to identify the mass spectra of the degradation products of each, followed by LC-HRMS analysis to determine the elemental composition and fragmentation patterns of the degradation products. The A-234 rate of hydrolysis kinetics were measured by 1H and 31P NMR spectroscopy in three of the decontaminants and when possible, two dimensional analysis was used to correlate the structural data from the chromatographic analysis. Lastly, the A-234 hydrolysate was derivatized via TMSDAM methylation for GC-MS/MS analysis after testing with two silylating and three methylating agents. Decontamination of A-234 was successful within 48 hours with three decontamination agents and complete hydrolysis was observed within 5 hours with an oxidizer-containing quaternary salt based decontamination agent.
  • Fu, Shu Yi Vicky (Helsingin yliopisto, 2022)
    Biomacromolecules are large particles found in biological fluids. The upregulations and downregulation of some biomacromolecules, such as extracellular vesicles (EVs) have been linked to cancer and infectious diseases. The study of these biological particles can help us in understanding the progression of those conditions better. Furthermore, studying naturally occurring biological molecules, e.g., immunoglobulin G (IgG), DNA, nucleic acids and glycoproteins can help us to gain more insight to important biological processes in the human body. The first part of this thesis is a literature review of monolithic columns in the separation of large biological molecules in liquid chromatographic and capillary electrochromatographic applications. Columns, including novel monolithic stationary phases, also known as monoliths, have been developed to counter some of the problems associated with the traditionally used packed beds in separation science. Monoliths have a unique structure of interconnecting porous channels, which allows faster separation with better resolution, reproducibility and mass transfer characteristics compared to packed beds. Organic-based polymer monoliths are the most widely used monolithic materials in biological applications, but the use of inorganic-based silica monoliths and hybrid monoliths have grown in the last couple of decades. Monolithic columns are versatile and they can be utilized in several chromatographic techniques, such as reversed-phase chromatography, affinity chromatography, ion-exchange chromatography, capillary electrochromatography and mixed-mode chromatography. Due to the growing interest, miniaturized monoliths e.g. in microfluidic devices, small capillaries and microarrays have been exploited to allow faster separation using sample volumes even as low as a few femtolitres. For higher sample throughput, monoliths in the format of 96-well plates, tips, sheets and disks have been introduced, especially for sample pre-treatment purposes. In the experimental part, affinity monolithic chromatography was employed for the isolation of lipoproteins and EVs in both exomere and exosome size range. The main function of EVs is transporting signal molecules from cell-to-cell to maintain homeostasis of the body. Low-density lipoprotein (LDL), very-low-density lipoprotein and chylomicrons are lipoproteins that transport different lipids in the human blood stream. The study of these particles is important because lipoproteins and especially LDL have been associated with atherosclerotic cardiovascular diseases. The experimental part of this thesis is focused on studying the feasibility of Convective Interaction Media (CIM) monoliths in disk (1.3 µm pores, 0.34 ml) and 96-well plate (2.1 µm pores, 0.1 ml) formats in purifying nanosized biomacromolecules from human plasma. The preparation of the affinity monoliths and the isolation of particles in the disk format was conducted following existing protocols and methods, which were modified for the monolithic 96-well plate. Six different monoclonal antibodies (mAbs), anti-CD9, anti-CD34, anti-CD61, anti-CD63, anti-CD81 and anti-CD82 were immobilized on the monolithic supports to target EVs. Anti-apoB100 mAb was used in targeting apolipoprotein B100 present on the surface of apoB100-containing lipoproteins. The isolation in the disk format was done using an on-line immunoaffinity chromatography – asymmetric flow field-flow fractionation method connected to ultraviolet, dynamic light scattering and diode array detectors. To compare the two different formats with different pore sizes in lipoprotein and EV isolation, the immobilization protocol and isolation conditions were optimized for the monolithic well plate. The isolation on the monolithic 96-well plate was done within 20 minutes, and the operation consumed three times less sample and buffer than in the disk format. Both monolithic formats were suitable for LDL isolation and the disks could also be used in EV isolation and separation. However, due to the larger pore size, EVs were found to be unstable in the monolithic wells.
  • Puumi, Jukka (Helsingin yliopisto, 2021)
    An overview on utilization of dual nickel/photocatalyst protocols to conduct aryl-heteroatom cross-coupling reactions is presented. Basic concepts of photocatalysis, including different relaxation pathways, the difference of singlet and triplet states, and parameters used to predict reactivity are first disclosed. The general components used in dual nickel/photocatalyst protocols are presented followed by the discussion on reactivity trends. The reactivity trends are compared with other common aryl-heteroatom cross-coupling protocols (Buchwald-Hartwig-, Ullmann- and Chan-Lam couplings) illustrating the general advantages and disadvantages of each cross-coupling method. The scope of different dual nickel/photocatalyst protocols are then explored, concentrating on cross-coupling of amines, alcohols/thiols and carboxylic acids. The developments in mechanistic understanding on the dual nickel/photocatalyst aryl-heteroatom cross-couplings in recent years are reviewed. It is concluded that photocatalytic single electron transfer-based cycles, proposed for a number of coupling protocols, are very unlikely to take place. It is made clear that, based on the current knowledge, two principle mechanism are reasonable: energy transfer or thermal Ni(I)/Ni(III) cycles. Problems concerning energy transfer mechanisms are also discussed. Finally, applicability of dual nickel/photocatalyst aryl-heteroatom cross-coupling for industrially significant transformations is briefly discussed.
  • Koivula, Juho (Helsingin yliopisto, 2021)
    Kirjallisuuskatsauksessa käydään läpi erilaisia menetelmiä C3-substituoitujen indolien synteeseihin 2-alkenyylianiliinityyppisistä lähtöaineista, joiden bentsyylinen asema oli substituoitu. Erityistä huomiota kiinnitetään menetelmiin, joiden reaktiomekanismeiksi ehdotettiin radikaalimekanismeja. Myös näitä ehdotettuja radikaalimekanismeja esitellään tutkielmassa. Kokeellisessa työssä tutkittiin C3-subsituoitujen indolien hapettavaa synteesiä hiilikatalyytin avulla. Lähtöaineina käytettiin bentsyylisesti aryylisubstituoituja 2-alkenyylianiliinijohdannaisia. Joidenkin lähtöaineiden typpeen oli kiinnitetty metoksipyridiini, jonka kiinnitystä varten kehitettiin Buchwald-katalyysi. Hiilikatalyysit tuottivat hyviä saantoja. Korkea elektronitiheys, etenkin aniliinin bentseenirenkaan ja/tai typen aromaattisen substituentin korkea elektronitiheys, oli eduksi. Reaktion mekanismin ehdotetaan alkavan hapettumisella radikaalikationiksi, ja näitä hapetuspotentiaaleja laskettiin aiemmin raportoidun menetelmän mukaisesti. Mikäli indolin 5-renkaan substituutiot (N1, C2, C3) olivat tarpeeksi samankaltaisia, korkea elektronitiheys, matala hapetuspotentiaali ja hyvä saanto korreloivat. Indolin 5-renkaan substituutio on kuitenkin merkittävämpi tekijä kuin hapetuspotentiaali ja/tai korkea elektronitiheys. Pyridiini typen suojaryhmänä toimi katalyysissä ja se onnistuttiin poistamaan helposti. Metoksipyridiini toimi katalyysissä hyvin, mutta sen kvantitatiivinen poistaminen ei onnistunut.
  • Känsäkoski, Silja (Helsingin yliopisto, 2023)
    Lignin is an abundant aromatic polymer found in renewable biomass sources such as trees and grasses. Lignin is largely formed as a side product in paper and pulping industries, and recent research has been trying to valorize it for value-added products such as fuels and chemicals through catalytic depolymerization. This thesis work consists of two parts: a literature review on lignin and it depolymerization methods and the experimental part where lignin is depolymerized, and the products are analyzed. In the literature review an overview of lignin, its structure and different sources is given. Furthermore, different extraction methods of lignin from the biomass source are reviewed, and more specifically the organosolv process is highlighted. Different products formed in the depolymerization of lignin are presented along with their applications. Depolymerization methods including pyrolysis, oxidative depolymerization, solvolysis and reductive depolymerization are reviewed. Finally, different metal catalysts, with a focus on molybdenum-based ones, used in reductive lignin depolymerization are presented. In the experimental part two molybdenum phosphide catalysts are synthesized and characterized. They are used in the depolymerization of fraunhoferk130 and GVL lignin using ethanolysis in a batch or autoclave reactor. The mass balance of product fractions and monophenol yields are presented. Monophenol yields ranged from 3.5 wt.% to 22.8 wt.%. Additional hydrogen pressure suppresses repolymerization and char formation but has negative impact on monomer yields so the true role of hydrogen gas remains unclear. Increasing reaction temperature led to smaller molar mass but higher char formation. The different catalysts used are compared in the results with the help of the monomer yields, mass balance and molar masses. Overall, the molybdenum-based catalysts showed promise as monomer yields were in lieu of those found in literature and can be synthesized with lower costs than noble metal catalysts.
  • Tynkkynen, Jere (Helsingin yliopisto, 2022)
    This paper features two parts; a literature review discussing the recent development in using electrochemical gas sensors for pollutant detection and the use of sensor nodes in real-life locations, and an experimental section focusing on the kinetic study of nitrogen containing compounds utilizing in-tube extraction device. Growing interest towards personal safety have led to development of low-cost electrochemical sensors for personal safety, indoor air quality and leak detection applications. Heterojunctions and light illumination have emerged as an effective way to improve sensor performance, but the selectivity of electrochemical sensors remains relatively poor. Multiple sensors can be combined to create ‘E-noses’ which significantly improve the selectivity and compound identification. These E-noses have been deployed in some indoor locations, either being stationary in sensor networks or moved around by a robot or drone. All approaches have benefits and caveats associated to them, with the differences between individual sensors limiting sensor network use, and slow response and recovery times limiting the use of moving sensors. A novel micropump system was constructed to be used in the active air sampling together with in tube extraction (ITEX) and thermal desorption gas-chromatography (TD-GC-MS). The repeatability of this method was tested in a kinetic study of 10 selected nitrogen containing compounds in a custom-built permeation chamber. The breakthrough times and volumes of the compounds were investigated. Kinetic modelling was successful for 9 out of the 10 compounds with 1 compound behaving significantly different from the rest. The breakthrough times were always over 20 minutes and breakthrough volumes were around the 1000 ml region. Reproducibility was tested with multiple ITEX’s and samples were taken from five indoor locations. Three of the tested compounds were found in some of the samples.
  • Gabbouj, Selma (Helsingin yliopisto, 2022)
    Chemical attribution encompasses the detection and characterization of compounds of interest to find signature impurity, isotopic, and elemental profiles, which can be used to link illegal material to specific manufacturers, stocks, precursors, synthetic routes, or geographical locations. Explosives have been increasingly used for criminal purposes world-wide due to the availability of explosive material, precursors, and synthesis instructions. Nitrate ester, nitramine, and nitroaromatic military explosives as well as homemade organic peroxides are examples from over 250 explosive materials listed in the 2020 Federal Register of the US Bureau of Alcohol, Tobacco, Firearms, and Explosives. The first part of the thesis is a literature review, which aims to 1) present published mass spectrometric (MS) and liquid chromatographic (LC) detection methods for explosives and 2) explore chemical attribution studies of explosives and related compounds, such as illicit drugs and chemical warfare agents. The second part presents the experimental research carried out at the Finnish Institute for Verification of the Chemical Weapons Convention (VERIFIN), which aims to 3) develop an analysis method for multiclass explosives using liquid chromatography-high resolution mass spectrometry (LC-HRMS) and 4) perform chemical attribution of the nitrate ester explosive pentaerythritol tetranitrate (PETN) from different sources by isotopic and impurity profiling. Multiclass explosives detection required optimization of MS parameters, such as lower ion transfer tube and vaporizer temperatures and negative ion detection mode, as well as introduction of additives into LC eluents to promote adduct formation. PETN, 1,3,5-trinitro-1,3,5-triazinane (RDX), 1,3,5,7-tetranitro- 1,3,5,7-tetrazocane (HMX), 2,4,6-trinitrophenyl-methylnitramine (tetryl), 2-amino-4,6-dinitrotoluene (2- ADNT), and 4-amino-2,6-dinitrotoluene (4-ADNT) were detected from a mixture as nitrate adducts. Optimal parameters for the isotopic profiling of PETN were found to be 500 000 resolution, 2E4 (5 %) automatic gain control (AGC) target, and 50 ms injection time. Student’s t-tests revealed statistically significant differences between oxygen isotope ratio (18O/16O) values of PETN from two different sources. However, lack of repeatability of the isotope ratio results was an issue. 7 different methods were tested for the impurity profiling of PETN. Samples were rather pure but clear differences in the high mass range (m/z 600–900) impurity profiles of the two types of PETN were discovered, leading to the conclusion that they are indeed from different sources. Tentative structures of PETN homologue derivatives were assigned to the impurities using MS2 fragmentation and literature. Based on the results of this work, LC-HRMS is suitable for impurity analysis even for pure samples, but not very efficient or practical for analyzing isotope ratios.
  • Martinmäki, Tatu (Helsingin yliopisto, 2020)
    Tiivistelmä – Referat – Abstract Molecular imaging is visualization, characterization and quantification of biological processes at molecular and cellular levels of living organisms, achieved by molecular imaging probes and techniques such as radiotracer imaging, magnetic resonance imaging and ultrasound imaging. Molecular imaging is an important part of patient care. It allows detection and localization of disease at early stages, and it is also an important tool in drug discovery and development. Positron emission tomography (PET) is a biomedical imaging technique considered as one of the most important advances in biomedical sciences. PET is used for a variety of biomedical applications: i.e. imaging of divergent metabolism, oncology and neurology. PET is based on incorporation of positron emitting radionuclides to drug molecules. As prominent radionuclides used in PET are of short or ultra-short half-lives, the radionuclide is most often incorporated to the precursor in the last step of the synthesis. This has proven to be a challenge with novel targeted radiotracers, as the demand for high specific activity leads to harsh reaction conditions, often with extreme pH and heat which could denature the targeting vector. Click chemistry is a synthetic approach based on modular building blocks. The concept was originally developed for purposes of drug discovery and development. It has been widely utilized in radiopharmaceutical development for conjugating prosthetic groups or functional groups to precursor molecules. Click chemistry reactions are highly selective and fast due to thermodynamic driving force and occur with high kinetics in mild reaction conditions, which makes the concept ideal for development and production of PET radiopharmaceuticals. Isotope exchange (IE) radiosynthesis with trifluoroborate moieties is an alternative labeling strategy for a reasonably high yield 18F labeling of targeted radiopharmaceuticals. As the labeling conditions in IE are milder than in commonly utilized nucleophilic fluorination, the scope of targeting vectors can be extended to labile biomolecules expressing highly specific binding to drug targets, resulting to higher contrast in PET imaging. A trifluoroborate functionalized prosthetic group 3 was synthetized utilizing click chemistry reactions, purified with SPE and characterized with HPLC-MS and NMR (1H , 11B-, 13C-, 19F-NMR). [18F]3 was successfully radiolabeled with RCY of 20.1 %, incorporation yield of 22.3 ± 11.4 % and RCP of >95 %. TCO-functionalized TOC-peptide precursor 6 was synthetized from a commercial octreotide precursor and a commercially available click chemistry building block via oxime bond formation. 6 was characterized with HPLC-MS and purified with semi preparative HPLC. Final product [18F]7 was produced in a two-step radiosynthesis via IEDDA conjugation of [18F]3 and 6. [18F]7 was produced with RCY 1.0 ± 1.0 %, RCP >95 % and estimated molar activity of 0.7 ± 0.8 GBq/µmol. A cell uptake study was conducted with [18F]7 in AR42J cell line. Internalization and specific binding to SSTR2 were observed in vitro.
  • Brasseur, Paul (Helsingin yliopisto, 2021)
    Plasmonic is an emerging field which has showed application for photocatlysis. Here we investigate a gold/platinum bimetallic catalytic system, and try to show how the catalytic properties of gold nanoparticles can be us to harvest visible light energy to increase the catalytic activity of platinum. Platinum being are rare and expensive metal, we also took the opportunity to find the optimal amount of catalyst to reduce platinum use. The catalyst is composed of a core spherical gold nanoparticles, of around 15 nm diameter. They were synthesized using an inversed Turkevich method, based on trisodium citrate, gold precursor salt and done in solution. Various amount of platinum was deposited on those nanoparticles using seeded growth method. The amount of platinum varied for single atoms to an atomic monolayer. This suspension of nanoparticles was deposited on ultrafine silica powder to be used for certain reaction and characterization. The material was characterized via several technics. UV-Visible and Diffuse Reflectance Spectroscopy were used to characterize its optical properties and showed a absorption peak around 524 nm characteristic of gold nanoparticles of this size. Imaging was done using electron microscopy (SEM and TEM) to study the morphology and showed monodisperse and spherical particles. The exact composition of the different catalyst were obtain using Atomic Emission Spectroscopy. The study was conducted by using reduction reaction as tests to investigate differences in conversion and selectivity under dark and monochromatic 525 nm and 427 nm light conditions. We chose to work on reduction of 4-nitrophenol, phenylacetylene and nitrobenzene, because they are widely used both in research and industry, and are easy to set up. Some catalyst showed good enhancement under 525 nm light, especially the one with the least amount of platinum. Different selectivity were also observed, indicating the presence of different reaction pathways under light conditions.
  • Pusfitasari, Eka Dian (Helsingin yliopisto, 2019)
    Urine can be used to determine human exposure to nerve agents through the analysis of specific biomarkers. Isopropyl methylphosphonic acid (IMPA) is an important marker of sarin nerve agent, a highly toxic chemical regulated under the Chemical Weapons Convention (CWC). A methodology for sensitive, reliable, and selective determination of IMPA in urine matrix was developed and validated, using liquid chromatography-tandem mass spectrometry (LC-MS/MS). The sample preparation method employs normal phase–solid phase extraction (NP-SPE) using silica based cartridge. Before conducting IMPA analysis, the instrument performance was controlled using a quality control sample. Three different ion sources, namely electrospray ionization (ESI), Unispray, and atmospheric pressure chemical ionization (APCI), were compared in order to define the best method for trace analysis of targeted IMPA. Parameters affecting the ionization process such as cone voltage, capillary voltage, impactor pin voltage, corona voltage, and mobile phase flow rate were optimized. Negative ion mode was selected as the best method for IMPA identification in all three ion sources, and multiple reactions monitoring (MRM) was employed to improve sensitivity and selectivity. The APCI source was shown to be the least sensitive and least efficient ionization technique for IMPA identification. In contrast, using ESI and Unispray resulted in satisfactory data with excellent limit of detection (LOD), limit of quantification (LOQ), precision, and accuracy. The two latter ion sources share the same values of those parameters, i.e. 0.44 ng/mL, 1.46 ng/mL, < 4% precision bias, < 5% accuracy bias, for ESI; and 0.42 ng/mL, 1.38 ng/mL, < 4% precision bias, < 4% accuracy bias, for Unispray. Nonetheless, the Unispray shows better performance in comparison to ESI in producing higher signal intensity/peak area and has lower matrix effect.
  • Komarczuk, Elise (Helsingin yliopisto, 2022)
    The most common route to administer drugs is oral drug delivery. However, the effectiveness of a drug or bioavailability depends mainly on the drug solubility and many drugs or drug candidates are poorly water-soluble. This is the case of indomethacin, a nonsteroidal anti-inflammatory drug (NSAID), widely used against arthritis. The drug solubility and hence the bioavailability can be improved by formulation. The formulation can be prepared with an amphiphilic compound, for instance amphiphilic block copolymers like Poly(2-oxazoline)s that have proven to be suitable candidates because they are biocompatible and their solubility and solubilization capacity can be widely modulated. Since after oral administration, the drug will be absorbed in the intestine, the intestinal fluid plays a crucial role in the solubilization, but this is currently poorly understood. Therefore, drug interactions studies are made in solution mimicking fed state intestinal fluid (FeSSIF-V2) composed of lipids (fatty acids FA and lecithin LC) and bile salts (taurocholic acid, TC). Subject of this study was the investigation of the interaction between indomethacin with poly(2-oxazoline) ABA triblock copolymers, (P2), comprising poly(2-methyl-2-oxazoline) as hydrophilic blocks and poly(2-butyl-2-oxazoline) as hydrophobic blocks, and FeSSIF-V2 were carried out using the different NMR techniques such as Diffusion-Ordered NMR spectroscopy (DOSY), nuclear Overhauser effect spectroscopy (NOESY) and 1H-NMR regarding the changes in chemical shift, the changes of the intensities and the integrals Indomethacin alone, polymer P2 alone and P2-Indomethacin formulations were dissolved in FeSSIF-V2. The changes in chemical shift proved that interactions exist between the drug, the formulation and the FeSSIF-V2. It was found (with the changes in chemical shifts, confirmed by DOSY) that the indomethacin interacts with the bile salts (TC). Also the DOSY experiment showed that the polymer P2 interacts with the bile salts (TC) at low concentration and with the lipids at a polymer concentration greater than 0.3 wt%. The same experiment was done using the P2-Indomethacin formulations and at the concentration of 0.3 wt% again the polymer aggregates were going from interacting with the bile salts (TC) to merging with the lipid aggregates, presenting a significant increase of hydrodynamic diameter (from 3.5 nm to 6.2 nm).
  • Tuna, Yasemin (Helsingin yliopisto, 2023)
    Nuclear power plant decommissioning is a difficult process that combines industrial decommissioning techniques, radiation safety standards, and legal requirements for the final disposal of nuclear waste. The goal of nuclear decommissioning is to completely purge the plant of all radioactive material so that it can be released from regulatory oversight. The range of corrosion products generated on the steel surface are known to have a significant impact on the corrosion process of steel. Corrosion products have a complicated structure. The corrosion products are created when metallic components, mostly iron, react with oxygen and water that are drawn from the atmosphere, and their structure is then significantly influenced by environmental factors. Quantitative characterisation of the atomic scale structure of corrosion products is critically needed for identifying the corrosion products reliably. This thesis provides the characterization process of corrosion products formed on the steel surfaces and this process was executed with the help of XRD (X-ray Diffraction), SEM/EDS Scanning Electron Microscope/ Energy Dispersive Spectrometry, and Raman spectroscopy. Within the scope of this project, besides characterization of steel samples, Loviisa ground water and synthetic water samples which have been in a long-term contact with activated steel samples were also examined. Separation processes was carried out for determining Fe-55 and Ni-63 in the waters and the presence of Co-60 was removed from the samples before the activity determination of Fe-55 and Ni-63 by LSC (Liquid Scintillation Counting). This master's thesis has been carried out in connection with the DEMONI project, which has been a coordinated project of VTT and the University of Helsinki (KYT2022 Research Program). The outcome of the thesis will benefit possible decommissioning and disposal strategies for the nuclear power plant's reactor pressure vessels.
  • Sillanpää, Meri (Helsingin yliopisto, 2021)
    The literature study of this thesis focuses on the different analytical methods used to analyse amino acids in food and beverage samples. Amino acids are essential organic molecules and their concentrations in foods and beverages constitute, inter alia, the product’s nutritional value, quality, freshness, and flavour. Amino acid analysis of foodstuff has various applications, which exploit several analytical methods. These reviewed methods are founded on academic articles published during the past two decades. This literature review discusses the different sample matrixes, sample preparation methods, ways to derivate analytes, and different separation and detection methods utilized in the recent amino acid studies. The experimental part of this thesis was a modification of L-asparagine and L-aspartic acid test (L-Asp/L-AspAc) in Thermo Fisher Scientific Oy industrial R&D laboratory. An enzymatic photometric method is used to determine L-Asp/L-AspAc amino acids in food samples. The modification process entailed pre-testing of several candidate methods, from which the most suitable one was selected. The feasibility of the chosen test was affirmed before verification and validation of the modified test.
  • Tanskanen, Ville (Helsingin yliopisto, 2020)
    Microbial volatile organic compounds are emitted by diverse set of microbial organisms and they are known to cause health hazards when present in indoor air. Early detection of fungal contaminated buildings and species present is crucial to prevent health problems caused by fungal secondary metabolites. This thesis focuses on analysing emission profiles of different insulation materials and fungal cultures, which allows, in further studies, to develop efficient new ways to detect fungi from contaminated buildings. Studied insulation materials consisted of cellulose and glass wool, which were analysed in multiple different conditions. Humidity of atmosphere was varied between 0-10 microliters and temperature was varied between 30°C and 40°C. In fungal emission profile study 24 different cultures were analysed in two different atmospheres, ambient and micro- aerophilic, and in multiple different inoculums. Analysis for both insulation materials and fungal cultures was done using headspace solid phase microextraction Arrow -tool and headspace in tube extraction –tool together with gas chromatography – mass spectrometry. One goal for this thesis was also test suitability of these methods for detection of fungal secondary metabolites. Comprehensive fungal emission profiles were successfully formed and new information from behaviour of insulation materials in different settings was found. In addition, new information about analysis methods and fungal behaviour in different atmospheres was found. Headspace solid phase microextraction Arrow with gas chromatography – mass spectrometry was found to be efficient, sensitive and timesaving method for indoor air study purposes. There were also many potential fungal culture specific biomarker compounds found for further study purposes.