Browsing by study line "Chemistry"

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.

This study focuses on analyzing dust samples with gas chromatography coupled with mass spectrometer. Humans get exposed to dust daily and it is important to know the risks this exposure brings. Dust is a complex, mainly organic matrix, which absorbs compounds easily. Some of these absorbed compounds have adverse effects on human health. To identify these harmful compounds from samples, they must be extracted into a solvent and possibly cleaned, so that they can be analyzed with gas chromatography coupled with a mass spectrometer system. Analysis of dust samples requires the right gas chromatography column, which can separate analytes of interest and a mass spectrometer with an ion source that can be used to analyze the sample qualitatively and/or quantitatively depending on the depth and type of the study. Along with samples, standards are used in quality control of the analysis method and in finding limitations of the method. Methods and results of the studies used in this thesis are compiled into tables. Sources and health effects of found compounds are discussed. In the experimental part of the thesis, analysis of dust samples from Finnish museums was done for the Finnish Institute of Occupational Health. These samples were concentrated and analyzed with gas chromatography coupled with a mass spectrometer system. The system had calibration issues, which had to be solved before the data it provided was usable. After the calibration issue was fixed, the analysis results were obtained and studied. In these results many harmful compounds were found, of which many were related to the preservation of the items housed in the museums. The compounds' health effects were studied and tabulated. These results show that further studies are required for dust samples to avoid exposure to compounds found in them.

Sizing agents are chemical additives used in paper and board making to improve hydrophobicity and to control the water penetration into the fiber network. This thesis reviews various analytical methods that have been reported to analyze three sizing agents: alkyl ketene dimer (AKD), alkenyl succinic anhydride (ASA), and rosin. Overview of the analytical methods includes gas chromatography, high-performance liquid chromatography, and Fourier transform infrared spectroscopy, along with newer techniques like ultraviolet-visible absorption spectroscopy and near infrared spectroscopy. These agents are analyzed from various paper products, like paper, process waters and dispersion. While the goal is to retain all added sizing agents within the paper or board, complete retention is not achievable, and some agents are present in process waters. Analyzing sizing agent levels in process waters allows for the evaluation of sizing agent retention. In the experimental section, Kemira Oyj's AKD analysis method for process waters from paper mills is updated. The hazardous and possibly carcinogenic extraction Solvent A is replaced with the greener and safer Solvent B. Sample preparation is improved, reducing analysis time from six hours to one. Additionally, a new high performance liquid chromatography – evaporative light scattering detector (HPLC-ELSD) method is introduced, capable of simultaneously analyzing AKD and hydrolyzed AKD (HAKD) in a single chromatogram. This is the first time a HPLC method is reported for analyzing HAKD from process waters. This method achieves 99% recovery rates with 0.2 ppm LOQ for both AKD and HAKD.

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.

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.

As part of the SAFER2028, ABCRad (Alternative Buffer/Backfill Characterization and Radionuclide Interactions) research project, two alternative bentonite materials supplied by Posiva Oy were investigated in this thesis. The aim of the thesis was to investigate and determine the sorption behavior of these two buffer material candidates, with a deliberate reference to a well- known Na-Wyoming type bentonite serving as a benchmark. In order to closely imitate conditions relevant to repository settings, a synthetic reference water was prepared, and the experiments were conducted within a glove box in N2 atmosphere excluding CO2 and O2. This thesis provides valuable perspectives on the behavior and attributes of the alternative bentonite materials, which is crucial for guiding decisions in the design of repositories for radioactive waste and strategies for managing spent nuclear fuel. More specifically, this thesis provides thermodynamic sorption models (TMS) for two risk-driving radionuclides, uranium (U) and cesium (Cs). Batch sorption isotherms were made using a 1:20 solid-to-liquid ratio including 0.5 g of bentonite in 10 cm3 of reference water. Gamma spectroscopy and Liquid Scintillation Counting (LSC) were employed for the analysis of reaction supernatants. Complementary to these techniques, additional bentonite properties, including Cation Exchange Capacity (CEC) and Exchangeable Cations (EC), were determined. Pre-characterization was done for the bentonites using Fourier Transform Infrared Spectroscopy (FTIR) and the Specific Surface Areas (SSA) were determined. These analyses provide a comprehensive characterization of the alternative backfill materials under investigation. This thesis focuses on combining quantitative sorption data (e.g., distribution coefficient, Kd) with mechanistic understanding (e.g., FTIR spectroscopy). This contributes to an improved understanding of radionuclide sorption mechanisms, thereby bolstering safety considerations. The CEC determined for the bentonites, Laviosa, LMS, and Na-Wyoming were 87 (±0,048) meq/100 g, 95 (±0,34) meq/100 g, and 91 (± 1,23) meq/100 g, respectively. The distribution coefficient (Kd) values of uranium ranged from 130–135 cm3/g with Laviosa and 78–110 cm3/g with LMS, while those of cesium ranged from 130–280 cm3/g with Laviosa and from 150–425 cm3/g with LMS. Cesium demonstrated sorption of 95% within the 10-10 to 10-6 M range, decreasing slightly to 85–95% at concentrations up to 10-2 M. Uranium showed sorption in the range 80–100% across both clays, peaking at lower concentrations and declining at higher concentrations. These data align with those of the reference buffer material, indicating that these bentonites could potentially serve as feasible alternatives if they exhibit additional favorable sorption capacity with other risk-driving radionuclides (e.g., Eu, Ni, Th).

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.

I discuss recent work regarding electronic structure calculations on quantum computers. I introduce quantum computing and electronic structure theory, and then discuss different mappings from electrons and excitation operators, to qubits and unitary operators, mainly Jordan–Wigner and Bravyi–Kitaev. I discuss adiabatic quantum computing in connection to state preparation on quantum computers. I introduce the most important algorithms in the field, namely, quantum phase estimation (QPE) and variational quantum eigensolver (VQE). I also mention recent modifications and improvements to these algorithms. Then I take a detour to discuss noise and quantum operations, a model for understanding how quantum computations fail because of noise from the environment. Because of this noise, quantum simulators have risen as a tool for understanding quantum computers and I have used such simulators to do electronic structure calculations on small atoms. The algorithm I have used, QPE, yields the exact result within the employed basis. As a basis I use numerical orbitals, which are very robust due to their flexibility.

The thesis gives an overview of indoor air pollution sources, health effects, and the detection of the fungal markers in indoor environment. In the experimental part of the thesis, solid phase extraction-liquid chromatography-tandem mass spectrometry method was developed for the quantitative analysis of 23 fungal secondary metabolites. The method was used to analyze the condensate water in indoor air from two sick houses in the Southern part of Finland. Furthermore, the practice was used to find other possible fungal marker compounds. The concerns of the indoor air pollution have been steadily increasing for the past couple decades since the prevalence of the irritative symptoms, such as skin, eye and respiratory track problems, that have been increasing without any clear reasoning. These symptoms are therefore being referred as building related symptoms since no other functionality have been discovered to be responsible for those. The general sources that could be linked to the cause of these symptoms are comfort parameters, material and burning related sources, and microbial metabolism products. From the microbes, the fungal species exhibit biggest concerns related to the indoor air quality since the growth of the fungus in the suitable conditions can lead to sizeable emissions of the particles and secondary metabolites which might be toxic, irritating or otherwise unhealthy. The traditional way of detecting the fungal contamination has required highly trained professional who investigates the interiors of the suspected contaminated house with the help of a moisture detector. When the contaminated spot is detected, the expert would conduct a visual inspection, and take a sample of the fungal growth for the microscopic analysis. Since then, methods focusing on the detection of the fungal particles and compounds have been developed. These include the collection of the bioaerosols and the detection of the volatile organic compounds originating from the fungal metabolism. However, there are challenges and limitations on these methods such as dependencies on time, low concentrations, and other pollution sources having similar chemical profiles than the fungal sources. Therefore, diverse ways to analyze the chemical profile of the sick houses is needed. Consequently, in the experimental part of this thesis, the method was developed to analyze fungal secondary metabolites from the condensate of the indoor air. The investigation consisted of the two fungal contaminated sick houses and from the one reference laboratory air sample. The results revealed twelve compounds to be elevated in the indoor air compared to the outdoor air and seven of these compounds were not detected in the reference sample. From these seven compounds, the studied amino acids and caffeine were the most promising fungal marker compounds since these compounds had consistently larger concentrations indoors than outdoors. Furthermore, the precursor ion scan revealed nine more potential marker compounds.

In chemical forensics inorganic analysis is for example used to detect traces of explosives and drugs, to find residues of firearms, and as aid when searching for hidden burial sites. Forensic investigators also utilise inorganic information in chemical source attribution or fingerprinting, which seeks to identify chemical profiles of inorganic and/or organic compounds and elements that can provide information on the origin of the sample, how it has been produced and using which raw-materials. As the chemical profiles typically contain information for several compounds, comparison of profiles have to be analysed by multivariate statistical tools such as principal component analysis (PCA), hierarchical cluster analysis (HCA) and linear discriminant analysis (LDA). In this work the applicability of inorganic source fingerprinting on soil samples was investigated. For this an extraction procedure and an ion chromatographic (IC) method for the determination of F–, Cl–, Br–, NO3–, PO43–, SO42– and AsO43– in soil were developed and validated. Extraction of anions was done by microwave assisted solvent extraction, with good recoveries (86.15 % – 115.23 %) for nearly all recovery samples. The recovery of F– from soil was 174.77 %, due to enhanced extraction efficiency caused by the high extraction temperature. AsO43– could not be quantified due to low extractability and interfering matrix components. Development of a method for elemental analysis of soil samples by inductively coupled plasma mass spectrometry (ICP-MS) was also attempted. Complete dissolution was not achieved with microwave assisted acid digestion mainly because of the large particle size of the soils analysed. Samples were analysed for As, Co, Cr, Cu, Fe, Mn, Mo, Ni, V and Zn, but Ni could not be quantified from any of the samples because of the high detection limit caused by contamination of samples. Due to contamination and incomplete dissolution the variation in the results were large, leading to a large uncertainty for the results. Analysis of variance (ANOVA) revealed that there is a significant (α = 0.05) difference in the concentrations of all analytes but Mo and V between the samples. Two step PCA and LDA were performed on tha anion and elemental results separately. Better clustering of sample results were typically got with LDA than with PCA. LDA on the anion results was able to discriminate all samples while only four out of seven samples were identified by PCA. The large variation in the data meant that only the reference soil could be identified when all elemental concentrations were included. Removal of outliers from the data lead to identification of all samples by both PCA and LDA. This work showed that samples can be identified by their inorganic profiles, but large variations in the measured concentrations will make the discrimination by multivariate statistics difficult. Further work should focus on improving the separation of the IC method and on decreasing the variation in the data by decreasing sample heterogeneity and contamination during the sample preparation.