Browsing by Subject "massaspektrometria"

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  • Kotiranta, Markus (Helsingin yliopisto, 2014)
    The literature review deals with the structure of arabinoxylan and the principles of mass spectrometric methods used in analyzing them. The fragmentation of carbohydrate structures, the structural information gained from it, and naming of the resulting neutral fragments and product ions was also discussed. The aim of the experimental work was to analyze linear xylo-oligosaccharides and branched or linear arabinoxylans with known structures using tandem mass spectrometry. Of the arabinoxylo-oligosaccharides analyzed, three were branched while the others had an arabinose substituent at terminal xylose. The oligosaccharides were analyzed as underivatized, alditols, and methylated alditols with both positive and negative ionization. Derivatization was done in order to produce different product ions and to gain information about the effect of reduction and methylation on fragmentation mechanisms. Underivatized oligosaccharides provided most information with negative mode ionization. Low intensity of C-type fragment ions prevented their isolation in MS3-step when reduced oligosaccharides were analyzed. Methylation changed the weights of fragmentation products, which made it possible to detect branching in the oligosaccharide structure. Methylation also changed the fragmentation mechanism which caused differences in the product ion spectra compared to underivatized oligosaccharides. B-ions were fragmented to gain information about linkage positions when analyzing methylated alditols. The mechanism of B-ion fragmentation differs from that of C-ions, and produced information rich neutral fragments. However, low signal intensity made branch site analysis difficult, especially when arabinose substituent was located at terminal xylose.
  • Backman, Nina (Helsingfors universitet, 2011)
    Screening of drugs of abuse has to combine sensitivity, selectivity and repeatability. The conventional screening methods include immunoassay screening followed by a more sensitive confirmation method. The aim of the study was to develop a simple, yet sensitive sample preparation method for screening of benzodiazepines and amphetamine derivatives in urine samples with silicon micropillar array electrospray ionization chip (µPESI) coupled to mass spectrometric analysis. Another aim was to evaluate the suitability of µPESI in biological sample analysis. Ideally, the developed method would provide an alternative to immunoassay screening method in forensic urine analysis. The sample preparation methods were separately optimized for benzodiazepines and amphetamine derivatives. Methods used included solid- phase extraction with Oasis HLB cartridge and C18-phase containing ZipTip®-pipette tip, liquid-liquid extraction, and dilution and filtering without prior extraction. Optimization focused, however, on ZipTip®-extraction. The compounds were spiked in blank urine to their cut-off levels, 200 ng/ml for benzodiazepines and 300 ng/ml for amphetamine derivatives. For benzodiazepines, every extraction phase was optimized. The sample pH was adjusted to 5, the ZipTip® phase was conditioned with acetonitrile and washed with a mixture of water (pH 5) and acetonitrile (10 % v/v) and the sample was eluted with a mixture of acetonitrile, formic acid and water (95:1:4 v/v/v). For amphetamine derivatives, pH values of sample and solvents were optimized. The sample pH was adjusted to 10, the ZipTip® phase was conditioned with a mixture of water and ammoniumbicarbonate (pH 10, 1:1 v/v), washed with a mixture of water and acetonitrile (1:5 v/v) and the sample was eluted with methanol. The optimized methods were tested with authentic urine samples obtained from Yhtyneet Medix Laboratories and compared to the results of quantitative GC/MS analysis. Benzodiazepine samples were hydrolyzed prior to extraction to improve recovery. All samples were measured with Q-TOF Micro apparatus and hydrolyzed benzodiazepine samples additionally with microTOF apparatus in Yhtyneet Medix Laboratories. Based on the results the developed method needs more optimization to function properly. The main problems were lack of reproducibility and poor sample ionization. Manual sample preparation and adding to the chip sample introduction spot increased variation. Authentic benzodiazepine samples gave false negative and authentic amphetamine derivative samples false positive results. False negatives may be due to the lack of sensitivity and false positives due to the contamination of sample cone, chips or solvents.
  • Fredrikson, Linda (Helsingin yliopisto, 2019)
    The consumption of omega (n-) 3 polyunsaturated fatty acids (PUFA) from fish has been associated with lower rates of cardiovascular diseases with one mechanism being lowering LDL cholesterol levels in blood. When incorporated into LDL particle n-3 PUFAs can modify the lipid composition and reduce atherogenicity of the particle, e.g. by influencing inflammatory processes. The effects of n-3 PUFA of plant origin are less studied. This study investigated the effects of Camelina sativa oil (CSO), a rich source of alpha-linolenic acid (ALA), on lipid species of human LDL including phosphatidylcholines (PC), lysophosphatidylcholines (LPC), sphingomyelin (SM), triacylglycerols (TAG) and cholesterol esters (CE). A total of 38 subjects with a history of impaired fasting glucose, were randomly divided into two groups; CSO (ALA 10 g/day) and the control group (limited fish and ALA intake) for 12 weeks. Blood samples were collected from the subjects at the beginning and at the end of the experiment after 12 weeks. LDL particles were isolated from blood and the lipids were analyzed by mass spectrometry. The CSO affected more the LDL core lipids (TAG and CE) than lipid species of the shell (PC, LPC, SM). CSO is high in ALA and linoleic acid (LA). Thus, the diet reduced mole fractions of lipid species containing saturated acyl chains while acyl chains in the core lipids with ALA, LA and EPA, that is formed in the body from ALA, were increased. Based on the results, having CSO in the diet changed the LDL particle lipid composition in a favorable direction for cardiovascular health.
  • Lindfors, Pia (Helsingfors universitet, 2010)
    The most important part in bioanalysis is the sample cleanup process which is usually the most laborious and time consuming part of the analysis and very susceptible to errors. A functional bioanalysis has to be quick, easily automated, sensitive, selective and stable. It also needs to be suitable for high throughput analysis. Desorption atmospheric pressure photoionization (DAPPI) is a novel direct desorption/ionization technique for mass spectrometry that enables direct analysis of solids from surfaces or liquid samples from a suitable sample plate often without any sample preparation. The suitability of DAPPI-MS for biological samples was investigated by measuring the limits of detection for selected opioids and benzodiazepines and screening them from authentic urine samples. Limits of detection were measured for standard solutions and spiked urine. Opioids and benzodiazepines were analyzed from post mortem urine samples with an optimized DAPPI-MS method. Post mortem urine samples were analyzed with and without sample preparation. Sample preparation improved the sensitivity of the method remarkably. About 50 % of the analytes were detected without sample preparation and almost 100 % after sample cleanup. It is however difficult to estimate the suitability of DAPPI-MS as a screening method because not all analyte concentrations of the urine samples were known. Therefore we cannot be certain weither the results obtained without sample preparation are caused by the suppression of the urine matrix or if the concentrations of the analytes are below the limits of detection. The reliability of the method can further be improved by investigating the metabolites of the analytes and improving the system towards automation. On grounds of this research DAPPI-MS should be used cautiously as a screening method for urine samples without sample preparation and with only high enough analyte concentrations. DAPPI-MS shows promise as a screening method for opioids and benzodiazepines from urine when the sample cleanup is used before the analysis.
  • Aalto, Henni (Helsingfors universitet, 2011)
    Lipids are fat soluble compounds that are derived from living tissues. Lipids have many important physiological functions. Developing methods for efficient lipid analysis is important since lipids can function as biomarkers in diseases. Additionally these methods can be used for the discovery of the biological processes of disease development. Lipids comprise of molecules with different polarity and structure. Several mass spectrometric ionization methods have been used in the analysis of lipids but they usually require sample preparation prior to the analysis. Desorption electrospray ionization-mass spectrometry (DESI-MS) and desorption photoionization-mass spectrometry (DAPPI-MS) are novel ionization methods that allow sample analysis straight from the matrix, such as tissue, usually without any sample preparation. DESI-MS has already been used in the analysis of different lipids, but DAPPI-MS has only been used in the analysis of steroids. The ionization of a range of lipid compounds (phospholipids, triglycerides, fat soluble vitamins, fatty acids, and steroids) by DAPPI-MS and DESI-MS was studied. Analysis conditions were optimized for all the different lipid classes with both DAPPI and DESI using standard samples. Some lipids were also analysed straight from pharmaceutical preparations. There were differences in the suitabilities of DAPPI-MS and DESI-MS for the ionization of different lipid classes. DAPPI-MS worked well for the ionization of nonpolar lipids like triglycerides, vitamins and fatty acids, but the phospholipids fragmented in the DAPPI-MS process and showed no molecular ion. Previous studies have shown that DESI-MS works well in the ionization of phospholipids, and this study showed that it works reasonably well for other lipid groups as well, with the exception of some of the nonpolar lipids. New knowledge was acquired especially about the suitability of DAPPI-MS for the analysis of different lipids. Based on the results it can be said that DAPPI-MS works equally well or better than DESI-MS in the ionization of most lipid classes. The DAPPI method should still be further developed so that phospholipids, which are very important lipids in human physiology, could be analysed by DAPPI-MS. As lipids were not analysed straight from a tissue sample, there are no conclusions about the suitability of DAPPI-MS for the analysis of lipids straight from tissue samples.
  • Mattila, Susanna (Helsingfors universitet, 2012)
    The aim of the stydy was to evaluate how different chemical derivatization methods are suitable for characterization of regional isomers of different glucuronide conjugates. Glucuronidation is one of the phase II metabolic reactions where more water soluble and often inactive substances are produced. Different functional groups may be subjected to glucuronidation. It is important to determine the exact position of glucuronidation, as the isomers may possess different toxicological or pharmacological properties. For example morphine-6-glucuronide is pharmacologically more active than morphine itself. The glucuronide conjugates are commonly detected by liquid chromatography tandem mass spectrometry (LC-MS/MS) and/or nuclear magnetic resonance (NMR). MS/MSspectra of native molecule and glucuronidated molecule are usually similar because of an initial loss of 176 Da, i.e. monodehydrated glucuronic acid. This fact often makes it impossible to determine the site of glucuronidation. Samples of NMR-analysis requires larger amounts of sample materials than MS-analysis. Many of those derivatization reagents tested in this study were not reacting as they were supposed to react according to literature. O-phthalaldehyde (OPA) and 9-fluorenylmethyl chloroformate (FMOC) were forming derivatives as expected and those reagents are very suitable for glucuronide conjugates studies. At the end of the studies the site of the glucuronidation of dopamine- and serotonineglucuronides were evaluated by derivatization with OPA and FMOC. Derivatization with OPA and FMOC successfully gave information about the region of the glucuronide acid in dopamine- and serotoninemolecules. The assumptions supposed to be correct according to NMR-studies presented in literature.
  • Mäkinen, Jarkko (Helsingfors universitet, 2014)
    Miniaturizing of analytical techniques in mass spectrometry has received a lot of attention amongst scientists. The gains of miniaturization of analytical systems are rapid analyses, lower solvent consumption, the option for automatization and lower costs. A glass-made microchip heated nebulizer and a newer version, steel-made nebulizer, have been recently developed. The aim of this study was to evaluate and compare performances of the nebulizers. Changes in test conditions and effects of different dopants to intensiveness of the analytes' signals were analyzed. Speed of nebulizer gas, speed of analyte flow and magnitude of heating were the parameters of the changes in test conditions. The temperature of the flow from the nebulizers was also measured and analyzed. The intensiveness profiles of the analytes between the nebulizers were unequal, when changes in the speed of nebulizer gas and magnitude of heating were measured. The nebulizers reacted the same way to changes of the speed of analyte flow. The faster the analyte flow was, the more intensive the analytes' signals were. The steel tube nebulizer generated on average more intensive signals of the analytes than glass-made microchip. Temperature of the glass-made nebulizer was considerably higher than that of steel tube nebulizer. The most intensive signals of the analytes were achieved when toluene was used as a dopant. Steel tube nebulizer was more efficient in ionizing analytes than glass-made microchip. However, with steel tube nebulizer it could be difficult to analyze compounds with high boiling point. One goal of this study was to combine the steel tube nebulizer with capLC, but due to technical failures of the capLC equipment this was not possible. In the future, it would be beneficial to improve the steel tube nebulizer's heating mechanism. Also it could be combined with other ionization techniques as has been done with glass-made nebulizer.
  • Saarelainen, Taija (Helsingfors universitet, 2010)
    Steroid hormones are involved in many physiological functions such as stress response and the maintenance of salt-water balance and pregnancy. Concentrations of steroids in the body fluids are generally very low (below ng/ml). Steroid hormones are metabolically associated and changes in mutual concentration levels of different steroids may signify a disease. Methods that allow the measurement of various steroids simultaneously are of great importance in investigating the role of steroid metabolism for example in formation of cancer. The aim of this work was to develop a sensitive and selective method for simultaneous quantification of 16 steroids in plasma. Nano liguid chromatography-microchip electrospray ionization-tandem mass spectrometry (nanoLC-µESI-MS/MS) was used in order to achieve good sensitivity. C18 enrichment column and separation column, and an electrospray tip were integrated onto the chip that was used in this work. Mass spectrometric parameters were optimized by using a MS calibration and diagnostic chip. It was noticed that the structure of steroids plays an important role on how the compound behave in electrospray ionization. Steroids with 4,5-ene-3-one-structure had much lower limits of detection than steroids without conjugated double bonds (0,075-0,5 ng/ml and 5-25 ng/ml respectively). The chosen sample pretreatment method to extract the steroids from plasma did not work properly, because it was able to extract only a third of the compound's real concentration. Analysis of some compounds was also difficult because of the background noise coming from plasma. The method development was therefore decided to continue with eight steroids that were well detectable and had 4,5-ene-3-one-structure. The limits of detection were 0,075-0,5 ng/ml in biological matrix for these compounds. Eight knock out and seven wild type mouse plasma samples were analyzed using the validated method. The method was able to quantify aldosterone, corticosterone and androstenedione. Developed method did not meet all the aims of this work. Derivatizated compounds, different equipment or totally new method should be used in order to accomplish the aims.
  • Kallio, Arttu (Helsingfors universitet, 2014)
    Cytochrome P450 (CYP) -enzymes are one of the most important enzymes in the metabolism of xenobiotics. Because many xenobiotics are metabolized with each other by the same CYP-enzymes, it is possible that metabolic interactions will take place. These interactions can be the inhibition or induction of the metabolism of another xenobiotic. The interaction can be harmful e.g. when it causes an accumulation of a toxic metabolite or when it inhibits the metabolism of an active drug substance. The aim of this study was to develop a quantitative method for determining metabolic interactions between drugs and environmental chemicals in human liver microsome (HLM) incubations. HLMs contain high concentrations of CYP-enzymes, enabling the use of CYP-model reactions for observing interactions. The model reactions chosen for this study were O-deethylation of phenacetin (CYP1A2), 7-hydroxylation of coumarin (CYP2A6), 4'-hydroxylation of diclofenac (CYP2C9), 1'-hydroxylation of bufuralol (CYP2D6) and 6β-hydroxylation of testosterone (CYP3A4). Michaelis-Menten constants (Km) and maximal enzymatic activities (Vmax) were determined for each model reaction. The suitability of the model reactions for inhibition studies was assessed with specific inhibitors. The quantitative method was developed for an ultra-high performance liquid chormatograph (UPLC) and for a quadrupole time of flight mass spectrometer (QTOF). Samples were ionized with electrospray ionization (ESI) using positive mode. Device parameters were the same for all the metabolites. The analytical method validation was partly performed according to ICH (International Conference on Harmonisation) guidelines. A sufficient linearity (R2>0,99) and specificity was achieved for the quantitative method. The achieved limits of quantitation (LOQ) were low enough (1-120 nM) for quantitation of the small concentrations of the metabolites formed in the inhibition assays. The measurement reproducibility and the reproducibility and accuracy of the method did not fulfill the acceptance criteria for all the metabolites. Improvement of the results should be tried by e.g. exploring different device parameters. 1'-hydroxydiclofenac was found likely to degrade in the matrix solution because of the acidic conditions, making the reliability of the results poor for this metabolite. The Km value obtained for coumarin differed markedly from literature values, which can be due to a too long incubation time. Therefore, incubation conditions should be optimized for this model reaction in coming studies. The Km values obtained for the model reactions of CYP1A2, CYP2D6 and CYP3A4 were similar to those found in literature. Also the IC50 values were quite well within the range of values reported in literature for the inhibitors of the above mentioned model reactions. The effects of four different polymers, F68, F127, Tetronic 1307 and polyvinyl alcohol (PVA) on the enzyme activities were also studied, at a concentration of 1 mg/ml. In principal, at this concentration the polymers did not cause significant changes in the enzyme activities, although inhibition of the CYP2C9 could have been significant. However, the reliability of CYP2C9 model reaction was found to be poor with the used method. In the future this developed method should be further validated, and the incubation conditions for the model reaction of CYP2A6 should be optimized. After this, the IC50 values for the polymers could be studied to get more reliable information about their potential CYP-inhibition properties.
  • Hossi, Heidi (Helsingfors universitet, 2016)
    The abuse of drugs is monitored by different authorities and health care. World Anti-Doping Agency (WADA) prohibits the use of doping substances and methods in- and/or out-of-competition. WADA has created strict instructions for Anti-Doping laboratories for analyzing different substances from biological samples. The aim of this study was to develop liquid chromatographic-mass spectrometric (LC-MS/MS) screening analysis for the detection in urine of drugs of abuse. The basis of study was 20 different substances which had different molecular weights, logP and pH values. The purpose was to create the basis of the method where is easy to add new analytes in further studies. Almost all substances chosen in this study were doping substances and the guidelines for the method were created by WADA. The sample pretreatment was pursued to be as generic as possible for plenitude of analytes and easy to perform. The sample pretreatment included two liquid-liquid extraction steps and enzymatic hydrolysis. The LC-MS/MS method worked well for many analytes with some exceptions. Some analytes didn't fit for the sample pretreatment and some didn't give strong enough signal in desired detection level. The gradient of LC-method can be limiting factor when adding new analytes to the method. Especially very lipophilic and polar analytes may cause difficulties. Carry over caused some problems in analyses. As a result it may lead to new sample treatment and LC-MSanalysis for the same batch.
  • Takala, Anna (Helsingfors universitet, 2012)
    Neurosteroids are steroids which are active in the central nervous system. They have many biological and physiological functions in human body. Fluctuations of the neurosteroid concentrations are related to many diseases such as depression, schizophrenia and epilepsy. Neurosteroid levels are measured to understand their role in brain function and human behavior. The aim of the work was to develop a gas chromatographic-atmospheric pressure fotoionization-tandem mass spectrometric (GC-APPI-MS/MS) method for analyzing 19 neurosteroids and their metabolites in urine. Neurosteroids are excreted in urine mainly as conjugates, so they have to be hydrolyzed before analysis. Sample purification is done by liquid-liquid extraction and the analytes are subsequently derivatized to enhance their volatility. Because widely used β-glucuronidase/arylsulfatase-enzyme from Helix pomatia oxidases 3β-hydroxy-5-ene and 3β-hydroxy-5α-reduced steroids, we decided to use β-glucuronidase from Escherichia coli and acid hydrolysis instead of H. pomatia. The quantification of the total neurosteroid concentration in urine was challenging because β-glucuronidase enzyme from E. coli did not hydrolyze glucuronides completely and acid hydrolysis deconjugated also glucuronides in addition to sulfate conjugates. In addition the internal standard d4-allopregnanolone was noticed to be impure and degrade during acid hydrolysis. The limits of detection were reasonably low for the method (2 pg/ml-1 ng/ml). The retention times of the analyte peaks were very repeatable (RSD 0,06-0,11%) and the repeatability of the method was acceptable for all compounds (RSD < 27%). Urine samples from two males and two females were analyzed with the preliminary validated method. We could determine estimated concentrations for dehydroepiandrosterone, dihydrotestosterone, androstenedione, testosterone, estrone, β-estradiol, estriol, 5α-tetrahydrodeoxocorticosterone, cortisone, corticosterone and hydrocortisone. The developed method did not meet all the aims of this work. The method needs further validation and more exact investigation about the effect of the selected hydrolysis method on intact steroids. Also the internal standard should be changed to some other compound, preferably a non-deuterated one.
  • Kuula, Matti (Helsingin yliopisto, 2020)
    Toisen maailmansodan jälkeen Itämereen upotettiin useita tonneja kemiallisia aseita ja niiden mukana myös ammusten sisältämät räjähdysaineet. Kemialliset räjähdysaineet, jotka ovat yleisimpiä räjähteitä, ovat joko yhdisteitä tai niiden seoksia. Pro gradu-tutkielman tarkoitus oli kartoittaa, voisiko taisteluaineanalytiikkaa varten tehtyjä menetelmiä hyödyntää myös räjähdeaineiden tutkimiseksi. Käytetyin analyysimenetelmä taisteluaineanalytiikassa on kaasukromatografi-massaspektrometri ja siksi tässä tutkimuksessa keskitytään siihen, vaikka joillekin räjähdeaineille nestekromatografia voisi olla parempi analyysitekniikka. Tutkielman kokeellisessa osiossa analysoitiin merenpohjassa olevia räjähdysaineita kaasukromatografi-kolmoiskvadrupolimassaspektrometrilla. Nopealla kaasukromatografimenetelmällä voitiin nopeuttaa analyysejä sekä vähentää yhdisteiden hajoamista kromatografisen erottumisen aikana. Tutkimuksessa hyödynnettiin nopeaa kaasukromatografiaa käyttäen kolmoiskvadrupolimassaspektrometriaa ja usean reaktion seurantaa. Näytteensyötössä käytettiin lämpötilaohjelmoitua injektointia. Tutkituista räjähdysaineista kaikki muut paitsi 1,3,5,7-tetranitro-1,3,5,7-tetratsoktaani (HMX) saatiin näkymään. Lisäksi kaasukromatografi-kolmoiskvadrupolimassaspektrometrilla suoritettavia lisätutkimuksia tarvitaan vielä seuraavien räjähteiden, nitroglyseriini (NG), pentaerytritoli tetranitraatti (PETN) ja metyyli-2,4,6-trinitrofenyylinitramiini (Tetryl), luotettavaksi määrittämiseksi.
  • Juvonen, Minna (Helsingfors universitet, 2011)
    The aim of the present study was to implement a tandem mass spectrometry (MS/MS) method for determining glycosidic bond linkage positions of neutral isomeric glucooligosaccharides. The methods for structural analysis and the fragmentation mechanisms of oligosaccharides in MS/MS-analysis was reviewed. The MS/MS-spectra of oligosaccharide contains glycosidic bond and cross ring cleavage fragment ions. The linkage position can be determined by cross ring cleavage fragment ions of cationized or anionized oligosaccharides. The study started by analyzing the typical MS/MS-spectra of model isomeric disaccharides with different linkage positions. The data was then used to assess the MS/MS-spectra of model tri- and tetrasaccharides. The similarity of MS/MS fragmentation patterns of the model disaccharides and the tri- and tetrasaccharides would enable the linkage position analysis by the applied MS/MS method. The MS/MS-analyses were carried out by using electron spray ionization with ion trap mass spectrometer in both positive and negative mode. In positive mode the oligosaccharides were analyzed as sodium and lithium adduct ions while chloride adduct ions were used in negative mode analysis. The different linkage positions of disaccharides were characterized by the different MS/MS fragmentation profiles in positive and negative ionization methods. The reducing end linkage positions of tri- and tetrasaccharides were easily identified by comparing their MS/MS fragmentation patterns with the MS/MS-spectra of model disaccharides. The other linkages in the tri- and tetrasaccharide were identified by using negative mode. In positive mode the identification of other linkages was not possible because the cross ring cleavage fragment ions were formed mostly from the reducing end. The linkages of tri- and tetrasaccharides could not be identified by MS3-analysis due to formation of isomeric glycosidic bond fragment ions as the charge can be retained in the reducing or non-reducing end. The results indicated that the applied MS/MS method was suitable for determing the glycosidic bond linkages of oligosaccharides in negative mode. In positive mode only the reducing end linkage can be determined.
  • Hannula, Juha (Helsingfors universitet, 2015)
    Ambient mass spectrometry includes methods where ions are produced outside of the mass spectrometry in atmospheric pressure direct from the surface of the sample without sample preparation. The first and most popular ambient ionization methods are DESI, desorption electrospray ionization and DART, direct analysis in real time. DAPPI, desorption atmospheric pressure photoionization is an ionization method where samples are desorbed with hot vapor from surface and then ionized by photoionization. The aim of this study was to develop desorption atmospheric pressure photoionization method in transmission geometry. In transmission geometry hot vapor for microchip is directed through metal or polymer meshes to mass spectrometer inlet. Liquid samples can be analyzed either by soaking the mesh to liquid sample or apply a sample droplet to the mesh. Hot vapor desorbs analytes from the mesh and analytes are ionized in a gas phase by photoionization using VUV lamp. In this method optimal positioning of the mesh and the microchip was determined. Additionally optimal microchip heating power, dopant flow rate, nebulizer gas flow rate, capillary voltage and drying gas parameters were determined. Optimized method was applied for analyzing standard samples, vitamin juice samples and milk samples. According the analysis with authentic samples, transmission mode DAPPI can be applied for analyzing liquid samples without sample preparation. According the analysis with standard samples, transmission mode DAPPI can be applied for extraction of hydrophobic analytes from water samples. Comparing to conventional DAPPI, in transmission mode DAPPI spectra, intensities of the background ions are lower resulting higher signal-to-noise ratios with transmission mode DAPPI.
  • Kontro, Hilkka (Helsingfors universitet, 2012)
    Core-fucosylation of N-glycoproteins is associated with different cancers and other pathologies. Identification of glycoproteins and determination of their glycan structure manually by mass spectrometry (MS) is time-consuming and laborious. In this Pro gradu thesis, the use of the mass spectrum-analyzing software Glycopeptide ID for identification of core-fucosylation from a known standard, immunoglobulin G, was studied. Also, a plasma sample with unknown glycoproteins was analyzed. For the MS analysis, the proteins were digested with trypsin, and the resulting glycopeptides were enriched using lectin affinity chromatography. From IgG and plasma, also samples treated with α-Lfucosidase were prepared in order to cleave the core fucose. The presence of glycopeptides was determined by high-performanve liquid chromatographymass spectrometry (HPLC-MS) analysis, and they were fragmented using collision-induced dissociation (CID) in a tandem-MS (MS/MS) analysis. The MS/MS spectra were analyzed with the Glycopeptide ID software. The software was found to identify core-fucosylation reliably from high-quality spectra, but identification of proteins were often incomplete from spectra with poor quality. From the plasma sample with unknown proteins, a probable corefucosylation was found from IgG2, fetuin A, serotransferrin, hemopexin and ceruloplasmin. As a conclusion, the software Glycopeptide ID can be considered as an appropriate tool for identification of core-fucosylation in N-glycopeptides.
  • Säilä, Pasi (Helsingfors universitet, 2016)
    Oxysterols and vitamin D related compounds are found to be biologically active in brain. They might be involved in different psychiatric and neurodegenerative diseases. These compounds have traditionally been analysed from tissues using somewhat laborious and time-consuming gas chromatograpy and liquid chromatography mass spectrometric methods. To the side of these methods ambient desorption ionization methods have been developed. The advantage of these methods is rapid and easy operation. Usually minimal or no sample pretreatment is required. In addition these methods can be applied to imaging of for example tissues. The aim of this work was to study if it is possible to detect certain oxysterols and vitamin D related compounds from rat brain tissue samples with desorption atmospheric pressure photoionization (DAPPI). The compounds chosen to this study were cholesterol, vitamin D3, 25-hydroxyvitamin D3, 7-dehydrocholesterol, desmosterol and 7-ketocholesterol. DAPPI is especially suitable for efficient ionization of this kind of neutral and non-polar compounds. Detected MS and MSn spectras of the brain tissue samples were compared to those obtained from standard compounds. As a result we could not detect vitamin D3, 25-hydroxyvitamin D3, 7-dehydrocholesterol, desmosterol from rat brain samples with DAPPI. Excluding vitamin D3 it is possible that those other analytes are present at the spectras of brain samples but there is some other compound with same mass which makes the reliable identification of studied compounds impossible. 7-ketocholesterol and cholesterol were the only compunds we detected from brain tissue sections. 7-ketocholesterol can be formed via auto-oxidation in samples containing excess amount of cholesterol. According to this study it is impossible to say if the detected 7-ketocholesterol is formed endogenously or during sample preparation and analysis.
  • Hietala, Eeva (Helsingfors universitet, 2015)
    The literature review deals with dyes in particular azo compounds and their chemistry, which are banned or permitted for the use in foodstuff. The literature review also deals with the analytical methods used for the determination of dyes in foodstuff. The main focus is on liquid chromatography and mass spectrometry. The aim of the experimental work was to develop and validate an UHPLC-MS/MS meth-od for the Finnish Customs laboratory for the simultaneous determination of multiple dyes in spices. The method included 37 different dyes that are either banned or permit-ted in foodstuff. The LC-MS/MS method development started by determining the pre-cursor ion as well as tree most abundant product ions for individual dyes. The next step was to optimize the liquid chromatographic method. This was carried out by running a standard mixture that included all of the dyes. The method for the extraction of dyes with acetonitrile in spices was developed so that it would be fast, easy and the maximum number of dyes would be extracted. Finally, the method was validated. The mass spectrometric method was developed for 37 dyes. Retention times were found for 35 of these dyes. The final runtime was 33 minutes. The extraction with acetonitrile was proven to work for 29 dyes. For the rest of the dyes, the extraction could be carried out with a different method. Only two of the colorants could not be extracted with the tested methods with the applied concentrations. For most of the dyes, the LOQs were 0,05-0,5 mg/kg. The method was repeatable concerning most of the dyes.