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  • 1.
    Abdel Rehim, Abbi
    et al.
    Stockholm University, Faculty of Science, Department of Analytical Chemistry.
    Abdel Rehim, Mohamed
    Stockholm University, Faculty of Science, Department of Analytical Chemistry.
    Screening and determination of drugs in human saliva utilizing microextraction by packed sorbent and liquid chromatography-tandem mass spectrometry2013In: BMC Biomedical chromotography, ISSN 0269-3879, E-ISSN 1099-0801, Vol. 27, no 9, 1188-1191 p.Article in journal (Refereed)
    Abstract [en]

    This study presents a new method for collecting and handling saliva samples using an automated analytical microsyringe and microextraction by packed syringe (MEPS). The screening and determination of lidocaine in human saliva samples utilizing MEPS and liquid chromatography-tandem mass spectrometry (LC-MS/MS) were carried out. An exact volume of saliva could be collected. The MEPS C-8-cartridge could be used for 50 extractions before it was discarded. The extraction recovery was about 60%. The pharmacokinetic curve of lidocaine in saliva using MEPS-LC-MS/MS is reported.

  • 2.
    Abdel-Rehim, Abbi
    et al.
    Stockholm University, Faculty of Science, Department of Analytical Chemistry.
    Abdel-Rehim, Mohamed
    Stockholm University, Faculty of Science, Department of Analytical Chemistry.
    Evaluation of microextraction by packed sorbent and micro-liquid chromatography-tandem mass spectrometry as a green approach in bioanalysis2013In: BMC Biomedical chromotography, ISSN 0269-3879, E-ISSN 1099-0801, Vol. 27, no 10, 1225-1233 p.Article in journal (Refereed)
    Abstract [en]

    In this study the use of micro-liquid chromatography coupled to tandem mass spectrometry (LC-MS/MS) was investigated in routine bioanalysis application for separation and quantification of pro-drug AZD6319 (developed for aldezheimer treatment). Microextraction by packed sorbent (MEPS) was used as sample clean-up method. The focus of this study was put on the evaluation of the usability of smaller column diameters such as 1.0 and 0.3mm instead of 2.1mm in bioanalysis application to reduce solvent consumption and sample volumes. Solvent consumption was reduced by 80% when a 1.0mm column was used compared with 2.1mm column. Robustness of the micro-columns in terms of accuracy and precision was investigated. The application of LC-MS/MS for the quantitative analysis of AZD6319 in plasma samples showed good selectivity, accuracy and precision. The coefficients of determination (R-2) were >0.998 for all runs using plasma samples on the studied micro-columns. The inter-day accuracy values for quality control samples ranged from 99 to 103% and from 96 to 105% for 0.3x50mm and 1.0x50mm columns, respectively. The inter-day precision values ranged from 4.0 to 9.0% and from 4.0 to 8.0% for 0.3x50 and 1.0x50mm columns, respectively. In addition the sensitivity was increased by three times using a 1.0mm column compared with 2.1mm. Furthermore, robustness of the micro-columns from different manufacturers was investigated.

  • 3. Abdel-Rehim, Abbi
    et al.
    Abdel-Rehim, Mohamed
    Stockholm University, Faculty of Science, Department of Analytical Chemistry.
    Advantages of Saliva Sampling in Bioanalysis Using Microextraction by Packed Sorbent and Dried Saliva Spot with LC-MS-MS2014In: LC GC Europe, ISSN 1471-6577, Vol. 27, no 10, 529-531 p.Article in journal (Refereed)
    Abstract [en]

    Saliva offers a fast and non-invasive sampling matrix for determining drug concentration levels, making it a suitable alternative to plasma and blood. During the analysis of biological samples attention is focused on sample pre-treatment. In addition, liquid chromatography coupled to tandem mass spectrometry (LC-MS-MS) is often the method of choice in bioanalysis because of the good selectivity and good sensitivity of the technique. In this article, two sample handling and sample preparation methods for saliva samples are presented and discussed. The first method is microextraction by packed sorbent (MEPS), and the second method is dried saliva spot (DSS). Both methods were applied for determining the presence of lidocaine in saliva.

  • 4. Abdel-Rehim, Abbi
    et al.
    Abdel-Rehim, Mohamed
    Stockholm University, Faculty of Science, Department of Analytical Chemistry.
    Dried saliva spot as a sampling technique for saliva samples2014In: BMC Biomedical chromotography, ISSN 0269-3879, E-ISSN 1099-0801, Vol. 28, no 6, 875-877 p.Article in journal (Refereed)
    Abstract [en]

    For the first time, dried saliva spot (DSS) was used as a sampling technique for saliva samples. In the DSS technique 50 L of saliva was collected on filter paper and the saliva was then extracted with an organic solvent. The local anesthetic lidocaine was used as a model compound, which was determined in the DSS using liquid chromatography and mass spectrometry. The results obtained for the determination of lidocaine in saliva using DSS were compared with those from a previous study using a microextraction by packed sorbent syringe as the sampling method for saliva. This study shows that DSS can be used for the analysis of saliva samples. The method is promising and very easy in terms of sampling and extraction procedures. The results from this study are in good agreement with those from our previous work on the determination of lidocaine in saliva. DSS can open a new dimension in the saliva handling process in terms of sampling, storing and transport.

  • 5.
    Abrahamsson, Maria
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Photochemistry and Molecular Science.
    Lundqvist, Maria
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Quantum Chemistry.
    Wolpher, Henriette
    Johansson, Olof
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Photochemistry and Molecular Science.
    Eriksson, Lars
    Bergquist, Jonas
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Physical and Analytical Chemistry, Analytical Chemistry.
    Rasmussen, Torben
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Biochemistry and Organic Chemistry.
    Becker, Hans-Christian
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Photochemistry and Molecular Science.
    Hammarström, Leif
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Photochemistry and Molecular Science.
    Norrby, Per-Ola
    Åkermark, Björn
    Persson, Petter
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Quantum Chemistry.
    Steric influence on the excited-state lifetimes of ruthenium complexes with bipyridyl-alkanylene-pyridyl ligands.2008In: Inorganic Chemistry, ISSN 0020-1669, E-ISSN 1520-510X, Vol. 47, no 9, 3540-3548 p.Article in journal (Refereed)
    Abstract [en]

    The structural effect on the metal-to-ligand charge transfer (MLCT) excited-state lifetime has been investigated in bis-tridentate Ru(II)-polypyridyl complexes based on the terpyridine-like ligands [6-(2,2'-bipyridyl)](2-pyridyl)methane (1) and 2-[6-(2,2'-bipyridyl)]-2-(2-pyridyl)propane (2). A homoleptic ([Ru(2)(2)](2+)) and a heteroleptic complex ([Ru(ttpy)(2)](2+)) based on the new ligand 2 have been prepared and their photophysical and structural properties studied experimentally and theoretically and compared to the results for the previously reported [Ru(1)(2)](2+). The excited-state lifetime of the homoleptic Ru-II complex with the isopropylene-bridged ligand 2 was found to be 50 times shorter than that of the corresponding homoleptic Ru-II complex of ligand 1, containing a methylene bridge. A comparison of the ground-state geometries of the two homoleptic complexes shows that steric interactions involving the isopropylene bridges make the coordination to the central Ru-II ion less octahedral in [Ru(2)(2)](2+) than in [Ru(1)(2))(2+). Calculations indicate that the structural differences in these complexes influence their ligand field splittings as well as the relative stabilities of the triplet metal-to-ligand charge transfer ((MLCT)-M-3) and metal-centered ((MC)-M-3) excited states. The large difference in measured excited-state lifetimes for the two homoleptic Ru-II complexes is attributed to a strong influence of steric interactions on the ligand field strength, which in turn affects the activation barriers for thermal conversion from (MLCT)-M-3 states to short-lived (MC)-M-3 states.

  • 6.
    Abrahamsson, Victor
    Linnaeus University, Faculty of Science and Engineering, School of Natural Sciences.
    Development of a fluorometric method for the quantification of sulfite and thiol-containing compounds in beer2011Independent thesis Advanced level (degree of Master (One Year)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    Sulfite is the most important antioxidant in beer. Quantification of sulfite is crucial due to restrictions as an additive and for investigative purposes of sulfite and thiol-containing proteins role as redox mediators. A method based on fluorometric determination of sulfite and thiol-containing compounds in beer was developed. The analytes were derivatized with ThioGlo®  1 and subsequently separated on a C18 column with wide pore size, featuring a high-performance liquid chromatography system equipped with fluorescence detector. Two peaks corresponding to sulfite derivatives were observed. The two derivatives were assessed with exact mass spectrometry and both provided identical mass spectra. To compensate for adverse matrix effects in samples a matrix-matched calibration curve is proposed. Sulfite diminished in an inverse exponential manner upon hydrogen peroxide addition in beer. The amount of thiol groups decreased when beer was subjected to oxidative stress, thus confirming its antioxidative role in beer.

  • 7.
    Abrahamsson, Victor
    et al.
    Linnaeus University, Faculty of Science and Engineering, School of Natural Sciences.
    Hoff, Signe
    University of Copenhagen, Denmark.
    Nielsen, Nikoline J.
    University of Copenhagen, Denmark.
    Lund, Marianne N.
    University of Copenhagen, Denmark.
    Andersen, Mogens L.
    University of Copenhagen, Denmark.
    Determination of Sulfite in Beer Based on Fluorescent Derivatives and Liquid Chromatographic Separation2012In: Journal of the American Society of Brewing Chemists, ISSN 0361-0470, E-ISSN 1943-7854, Vol. 70, no 4, 296-302 p.Article in journal (Refereed)
    Abstract [en]

    A method was developed for quantification of sulfite in beer based on derivatization with the maleimide-derived probe ThioGlo I followed by separation of fluorescent adducts by reversed-phase high-performance liquid chromatography and fluorescence detection. Sulfite gave two ThioGlo 1 derivatives and it was shown by mass spectrometry that both had identical mass spectra. Matrix effects were observed when constructing sulfite standard curves in different beers and, therefore, use of a matrix-matched calibration curve is proposed. ThioGlo I was found to generate fluorescent adducts with both bound and free sulfite, providing a quantification of the total sulfite content in beer. The limit of quantification of sulfite was 0.6 mg/L and the method can be used for quantification of sulfite in highly colored beers.

  • 8. Abuzooda, Thana
    et al.
    Amini, Ahmad
    Swedish Drug Agency,751 03 Uppsala, Sweden.
    Abdel-Rehim, Mohamed
    Graphite-based microextraction by packed sorbent for online extraction of β-blockers from human plasma samples2015In: Journal of chromatography. B, ISSN 1570-0232, E-ISSN 1873-376X, Vol. 992, 86-90 p.Article in journal (Refereed)
    Abstract [en]

    In the present work a new graphitic material (Carbon-XCOS) was used as a sorbent for microextraction by packed sorbent (MEPS). The β-blockers metoprolol and acebutolol in plasma samples were extracted and detected online using Carbon-MEPS syringe and liquid chromatography and tandem mass spectrometry (LC-MS/MS). Factors affecting the MEPS performance such as conditioning, washing and elution solutions were investigated. The validation of the bioanalytical method was performed using human plasma. The standard curve ranged from 10 to 2000nM and the lower limit of quantification (LLOQ) was set to 10nM. The method validation showed good accuracy and precision for the quality control (QC) samples at three concentration levels (30, 800 and 1600nM). The accuracy values of the QC samples were in the range of 86-108% (n=18). The precision values of intra- and inter-day for QC samples ranged from 4.4% to 14.4% (RSD) for the both studied analytes. The coefficient of determination (R(2)) values were ≥0.999 (n=3).

  • 9. Adler, Belinda
    et al.
    Boström, Tove
    KTH, School of Biotechnology (BIO), Proteomics.
    Ekström, Simon
    Hober, Sophia
    KTH, School of Biotechnology (BIO), Proteomics.
    Laurell, Thomas
    Miniaturized and Automated High-Throughput Verification of Proteins in the ISET Platform with MALDI MS2012In: Analytical Chemistry, ISSN 0003-2700, E-ISSN 1520-6882, Vol. 84, no 20, 8663-8669 p.Article in journal (Refereed)
    Abstract [en]

    A major bottleneck in high-throughput protein production is the validation step, which is why parallel and automated sample processing methods are highly desirable. Also, a miniaturized sample preparation format is preferred, as the reduction of reagent volumes significantly decreases the analysis cost per sample. We have developed an automated and miniaturized protein sequence verification protocol for recombinant proteins utilizing peptide mass fingerprinting and MS/MS analysis. The integrated selective enrichment target (ISET) platform, previously developed in our group, with its dual functionality, being both a sample preparation platform and a MALDI target plate, is employed. All steps including immobilized metal ion affinity chromatography of protein on cobalt-loaded beads, tryptic digestion, and MALDI MS analysis are performed in an array format, without any sample transfers, on the same ISET chip. The automated configuration reduced the sample preparation time significantly. Starting with crude lysate, a full plate of 48 purified, digested samples prepared for MALDI-MS can be generated in 4 h, with only 30 min of operator involvement. This paper demonstrates the utility of the method by parallel analysis of 45 His-tagged human recombinant proteins.

  • 10. Ahlgren, Joakim
    et al.
    De Brabandere, Heidi
    Reitzel, Kasper
    Rydin, Emil
    Gogoll, Adolf
    Waldeback, Monica
    Sediment phosphorus extractants for phosphorus-31 nuclear magnetic resonance analysis: A quantitative evaluation2007In: Journal of Environmental Quality, ISSN 0047-2425, E-ISSN 1537-2537, Vol. 36, no 3, 892-898 p.Article in journal (Refereed)
    Abstract [en]

    The influence of pre-extractant, extractant, and post-extractant on total extracted amounts of P and organic P compound groups measured with 31 P nuclear magnetic resonance (P-31-NMR) in lacustrine sediment was examined. The main extractants investigated were sodium hydroxide (NaOH) and sodium hydroxide ethylenediaminetetraacetic acid (NaOH-EDTA) with bicarbonate buffered dithionite (BD) or EDTA as pre-extractants. Post extractions were conducted using either NaOH or NaOH-EDTA, depending on the main extractant. Results showed that the most efficient combination of extractants for total P yield was NaOH with EDTA as pre-extractant, yielding almost 50% more than the second best procedure. The P compound groups varying the most between the different extraction procedures were polyphosphates and pyrophosphates. NaOH with BD as pre-extractant was the most efficient combination for these compound groups.

  • 11.
    Ahlgren, Joakim
    et al.
    Uppsala University, Teknisk-naturvetenskapliga vetenskapsområdet, Chemistry, Department of Physical and Analytical Chemistry, Analytical Chemistry. Department of Biochemistry and Organic Chemistry, Organic Chemistry I. Faculty of Science and Technology, Biology, Department of Ecology and Evolution, Limnology. Uppsala University, Teknisk-naturvetenskapliga vetenskapsområdet, Chemistry, Department of Physical and Analytical Chemistry.
    Reitzel, Kasper
    Danielsson, Rolf
    Uppsala University, Teknisk-naturvetenskapliga vetenskapsområdet, Chemistry, Department of Physical and Analytical Chemistry, Analytical Chemistry. Department of Biochemistry and Organic Chemistry, Organic Chemistry I. Faculty of Science and Technology, Biology, Department of Ecology and Evolution, Limnology. Uppsala University, Teknisk-naturvetenskapliga vetenskapsområdet, Chemistry, Department of Physical and Analytical Chemistry.
    Gogoll, Adolf
    Uppsala University, Teknisk-naturvetenskapliga vetenskapsområdet, Chemistry, Department of Physical and Analytical Chemistry, Analytical Chemistry. Department of Biochemistry and Organic Chemistry, Organic Chemistry I. Faculty of Science and Technology, Biology, Department of Ecology and Evolution, Limnology.
    Rydin, Emil
    Uppsala University, Teknisk-naturvetenskapliga vetenskapsområdet, Chemistry, Department of Physical and Analytical Chemistry, Analytical Chemistry. Department of Biochemistry and Organic Chemistry, Organic Chemistry I. Faculty of Science and Technology, Biology, Department of Ecology and Evolution, Limnology.
    Biogenic phosphorus in oligotropic mountain lake sediments: Differences in composition measured with NMR spectroscopy2006In: Water Research, no 40, 3705-3712 p.Article in journal (Refereed)
  • 12.
    Ahlgren, Joakim
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry, Analytical Chemistry.
    Tranvik, Lars
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Ecology and Evolution, Limnology.
    Gogoll, Adolf
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Biochemistry and Organic Chemistry, Organic Chemistry I.
    Waldebäck, Monica
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry, Analytical Chemistry.
    Markides, Karin
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry, Analytical Chemistry.
    Rydin, Emil
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Ecology and Evolution, Limnology.
    Sediment Depth Attenuation of Biogenic Phosphorus Compounds Measured by 31P NMR2005In: Environmental Science and Technology, ISSN 0013-936X, E-ISSN 1520-5851, Vol. 39, no 3, 867-872 p.Article in journal (Refereed)
    Abstract [en]

    Being a major cause of eutrophication and subsequent loss of water quality, the turnover of phosphorus (P) in lake sediments is in need of deeper understanding. A major part of the flux of P to eutrophic lake sediments is organically bound or of biogenic origin. This P is incorporated in a poorly described mixture of autochthonous and allochthonous sediment and forms the primary storage of P available for recycling to the water column, thus regulating lake trophic status. To identify and quantify biogenic sediment P and assess its lability, we analyzed sediment cores from Lake Erken, Sweden, using traditional P fractionation, and in parallel, NaOH extracts were analyzed using 31P NMR. The surface sediments contain orthophosphates (ortho-P) and pyrophosphates (pyro-P), as well as phosphate mono- and diesters. The first group of compounds to disappear with increased sediment depth is pyrophosphate, followed by a steady decline of the different ester compounds. Estimated half-life times of these compound groups are about 10 yr for pyrophosphate and 2 decades for mono- and diesters. Probably, these compounds will be mineralized to ortho-P and is thus potentially available for recycling to the water column, supporting further growth of phytoplankton. In conclusion, 31P NMR is a useful tool to asses the bioavailability of certain P compound groups, and the combination with traditional fractionation techniques makes quantification possible.

  • 13.
    Ahlgren, Sara
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - BMC, Analytical Chemistry.
    Fondell, Amelie
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - BMC, Analytical Chemistry.
    Gedda, Lars
    Uppsala University, Disciplinary Domain of Medicine and Pharmacy, Faculty of Medicine, Department of Immunology, Genetics and Pathology, Medical Radiation Science. Swedish Radiat Safety Author, Res Unit, Solna Strandvag 96, SE-17116 Stockholm, Sweden.
    Edwards, Katarina
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - BMC, Analytical Chemistry.
    EGF-targeting lipodisks for specific delivery of poorly water-soluble anticancer agents to tumour cells2017In: RSC Advances, ISSN 2046-2069, E-ISSN 2046-2069, Vol. 7, no 36, 22178-22186 p.Article in journal (Refereed)
    Abstract [en]

    Concerns regarding poor aqueous solubility, high toxicity and lack of specificity impede the translation of many hydrophobic anticancer agents into safe and effective anticancer drugs. The application of colloidal drug delivery systems, and in particular the use of lipid-based nanocarriers, has been identified as a promising means to overcome these issues. PEG-stabilized lipid nanodisks (lipodisks) have lately emerged as a novel type of biocompatible, nontoxic and adaptable drug nanocarrier. In this study we have explored the potential of lipodisks as a platform for formulation and tumour targeted delivery of hydrophobic anticancer agents. Using curcumin as a model compound, we show that lipodisks can be loaded with substantial amounts of hydrophobic drugs (curcumin/lipid molar ratio 0.15). We demonstrate moreover that by deliberate choice of preparation protocols the lipodisks can be provided with relevant amounts of targeting proteins, such as epidermal growth factor (EGF). Data from in vitro cell studies verify that such EGF-decorated curcumin-loaded lipodisks are capable of EGF-receptor specific targeting of human A-431 tumour cells, and strongly suggest that the interaction between the lipodisks and the tumour cells results in receptor-mediated internalization of the disks and their cargo.

  • 14.
    Ahlgren, Ulf
    Umeå University, Faculty of Medicine, Umeå Centre for Molecular Medicine (UCMM).
    Imaging shows insulin-producing cells in diabetes2013In: TrAC. Trends in analytical chemistry, ISSN 0165-9936, Vol. 44, III-III p.Article in journal (Other (popular science, discussion, etc.))
  • 15.
    Ahlinder, Jon
    et al.
    Totalförsvarets Forskningsinstitut, FOI, Stockholm, Sweden.
    Nordgaard, Anders
    Swedish National Forensic Centre (NFC), Linköping, Sweden.
    Wiklund Lindström, Susanne
    Totalförsvarets Forskningsinstitut, FOI, Stockholm, Sweden.
    Chemometrics comes to court: evidence evaluation of chem–bio threat agent attacks2015In: Journal of Chemometrics, ISSN 0886-9383, E-ISSN 1099-128X, Vol. 29, no 5, 267-276 p.Article in journal (Refereed)
    Abstract [en]

    Forensic statistics is a well-established scientific field whose purpose is to statistically analyze evidence in order to support legal decisions. It traditionally relies on methods that assume small numbers of independent variables and multiple samples. Unfortunately, such methods are less applicable when dealing with highly correlated multivariate data sets such as those generated by emerging high throughput analytical technologies. Chemometrics is a field that has a wealth of methods for the analysis of such complex data sets, so it would be desirable to combine the two fields in order to identify best practices for forensic statistics in the future. This paper provides a brief introduction to forensic statistics and describes how chemometrics could be integrated with its established methods to improve the evaluation of evidence in court.

    The paper describes how statistics and chemometrics can be integrated, by analyzing a previous know forensic data set composed of bacterial communities from fingerprints. The presented strategy can be applied in cases where chemical and biological threat agents have been illegally disposed.

  • 16.
    Ahmed, Trifa M.
    et al.
    Stockholm University, Faculty of Science, Department of Environmental Science and Analytical Chemistry.
    Bergvall, Christoffer
    Stockholm University, Faculty of Science, Department of Environmental Science and Analytical Chemistry.
    Westerholm, Roger
    Stockholm University, Faculty of Science, Department of Environmental Science and Analytical Chemistry.
    Emissions of particulate associated oxygenated and native polycyclic aromatic hydrocarbons from vehicles powered by ethanol/gasoline fuel blendsManuscript (preprint) (Other academic)
  • 17. Akter, Farhima
    et al.
    Mie, Masayasu
    Grimm, Sebastian
    KTH, School of Biotechnology (BIO), Molecular Biotechnology.
    Nygren, Per-Åke
    KTH, School of Biotechnology (BIO), Molecular Biotechnology.
    Kobatake, Eiry
    Detection of Antigens Using a Protein-DNA Chimera Developed by Enzymatic Covalent Bonding with phiX Gene A2012In: Analytical Chemistry, ISSN 0003-2700, E-ISSN 1520-6882, Vol. 84, no 11, 5040-5046 p.Article in journal (Refereed)
    Abstract [en]

    The chemical reactions used to make antibody DNA conjugates in many immunoassays diminish antigen-binding activity and yield heterogeneous products. Here, we address these issues by developing an antibody-based rolling circle amplification (RCA) strategy using a fusion of phi X174 gene A* protein and Z(mab2s) (A*-Zmab). The phi X174 gene A* protein is an enzyme that can covalently link with DNA, while the Z(mab2s) protein moiety can bind to specific species of antibodies. The DNA in an A*-Zmab conjugate was attached to the A* protein at a site chosen to not interfere with protein function, as determined by enzyme-linked immunosorbent assay (ELISA) and gel mobility shift analysis. The novel A*-Zmab-DNA conjugate retained its binding capabilities to a specific class of murine immunoglobulin gamma 1 (IgG1) but not to rabbit IgG. This indicates the generality of the A*-Zmab-based immuno-RCA assay that can be used in-sandwich ELISA format. Moreover, the enzymatic covalent method dramatically increased the yields of A*-Zmab-DNA conjugates up to 80% after a 15 min reaction. Finally, sensitive detection of human interferon-gamma (IFN-gamma) was achieved by immuno-RCA using our fusion protein in sandwich ELISA format. This new approach of the use of site-specific enzymatic DNA conjugation to proteins should be applicable to fabrication of novel immunoassays for biosensing.

  • 18.
    Aldaeus, Fredrik
    KTH, School of Chemical Science and Engineering (CHE), Chemistry.
    New Concepts for Dielectrophoretic Separations and Dielectric Measurements of Bioparticles2006Licentiate thesis, comprehensive summary (Other scientific)
    Abstract [en]

    This thesis presents two new concepts for separation of micro particles using dielectrophoresis, demonstrated by calculated examples, as well as a new method for obtaining dielectric data on living cells. The thesis is based on four papers.

    Paper I describes how the trapping efficiency of micro particles may be significantly increased when superpositioned electric fields are employed in a high conductivity medium. Avoiding low conductivity media is important when working with living cells. Calculations were performed to predict trajectories of Escherichia coli bacteria in the system with superpositioned electric fields, and a model was developed which employed two arrays of interdigitated electrodes in a micro channel.

    Paper II proposes a new concept for separation of micro particles, based on repetitive dielectrophoretic trapping and release in a flow system. Calculations show that the resolution increases as a direct function of the number of trap and release steps, and that a difference in size will have a larger influence on the separation than a difference in dielectrophoretic properties. Polystyrene beads in deionized water were used as a model, and calculations were performed to predict the particle behavior and the separation efficiency. It should be possible to separate particles with a size difference of 0.2 % by performing 200 trap-and-release steps. The enhanced separation power of multi step dielectrophoresis could have significant applications, not only for fractionation of particles with small differences in size, but also for measuring changes in surface conductivity.

    Paper III presents a new calculation method for predicting dielectrophoretic motion of micro particles. The method is based on a soft sphere method often used in molecular dynamics. Results from the calculations are in good agreement with theoretical predictions as well as initial experimental results, showing that the method provides good efficiency and accuracy.

    Paper IV describes a new method for measurements of conductivity of living bacteria. To obtain reliable conductivity values, it is important to handle the cells as gently as possible during the measurement process. A standard conductivity meter was used in combination with cross-flow filtration. In this way, repeated centrifugation and resuspension is avoided which otherwise may cause damage to the bacteria. The conductivity of Bacillus subtilis was determined to be 7000 μS/cm by means of the cross-flow filtration method, and the values differ from earlier published values by almost an order of a magnitude.

    In addition to the work presented in the papers, some experimental dielectrophoresis work in chip-based systems was performed. The behavior of Escherichia coli and polystyrene beads at different voltages and frequencies were studied. Separation of beads with different sizes was achieved on an array of interdigitated electrodes. Using electrodes with a pointed shape, alignment in different directions, pearl-chain formation, rotation, and other dielectrophoretic motion of E. coli were observed.

  • 19.
    Aldaeus, Fredrik
    Stockholm University, Faculty of Science, Department of Analytical Chemistry.
    New Tools for Trapping and Separation in Gas Chromatography and Dielectrophoresis: Improved Performance by Aid of Computer Simulation2007Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    Computer simulations can be useful aids for both developing new analytical methods and enhancing the performance of existing techniques. This thesis is based on studies in which computer simulations were key elements in the development of several new tools for use in gas chromatography and dielectrophoresis. In gas chromatography, gaseous analytes are separated by exploiting differences in their partitioning between different phases, and after their partitioning parameters have been determined the separations can be computationally predicted, and optimized, for a wide range of operating conditions. Similarly, in dielectrophoresis, particles with differing polarizability or size can be separated, and since particle trajectories within a separation device can be predicted using computations, the suitability of new designs, applications of forces and combinations of operational parameters can be assessed without necessarily making or empirically testing all of the variants.

    Using two existing numerical methods combined with semi-empirical determinations of retention behavior, temperature-programmed gas chromatograms were predicted with less than one percent deviations from experimental data, and a new method for improving the capacity of a gas-trapping device was predicted and experimentally verified. In addition, two new concepts with potential capacity to enhance dielectrophoretic separations were developed and tested in simulations. The first provides a promising way to improve the trapping of bacteria in media with elevated conductivity by using super-positioned electric fields, and the second a way to increase selectivity in the separation of bio-particles by using multiple dielectrophoretic cycles. The studies also introduced a more accurate method for determining the conductivity of suspensions of bacteria, and a new computational method for determining the dielectrophoretic behavior of particles in concentrated suspensions.

    The scientific studies are summarized and discussed in the main text of this thesis, and presented in detail in seven appended papers.

  • 20.
    Aldaeus, Fredrik
    et al.
    Stockholm University, Faculty of Science, Department of Analytical Chemistry.
    Thewalim, Yasar
    Stockholm University, Faculty of Science, Department of Analytical Chemistry.
    Colmsjö, Anders
    Stockholm University, Faculty of Science, Department of Analytical Chemistry.
    Prediction of retention times and peak widths in temperature-programmed gas chromatography using the finite element method2009In: Journal of Chromatography A, ISSN 0021-9673, E-ISSN 1873-3778, Vol. 1216, no 1, 134-139 p.Article in journal (Refereed)
    Abstract [en]

    Optimization of separations in gas chromatography is often a time-consuming task. However, computer simulations of chromatographic experiments may greatly reduce the time required. In this study, the finite element method was used to predict the retention times and peak widths of three analytes eluting from each of four columns during chromatographic separations with two temperature programs. The data acquired were displayed in predicted chromatograms that were then compared to experimentally acquired chromatograms. The differences between the predicted and measured retention times were typically less than 0.1%, although the experimental peak widths were typically 10% larger than expected from the idealized calculations. Input data for the retention and peak dispersion calculations were obtained from isothermal experiments, and converted to thermodynamic parameters.

  • 21.
    Aldaeus, Fredrik
    et al.
    Stockholm University, Faculty of Science, Department of Analytical Chemistry.
    Thewalim, Yasar
    Stockholm University, Faculty of Science, Department of Analytical Chemistry.
    Colmsjö, Anders
    Stockholm University, Faculty of Science, Department of Analytical Chemistry.
    Prediction of retention times of polycyclic aromatic hydrocarbons and n -alkanes in temperature-programmed gas chromatography2007In: Analytical and Bioanalytical Chemistry, ISSN 1618-2642, E-ISSN 1618-2650, Vol. 389, no 3, 941-950 p.Article in journal (Refereed)
    Abstract [en]

    We have developed an iterative procedure for predicting the retention times of polycyclic aromatic hydrocarbons (PAHs) and n-alkanes during separations by temperature-programmed gas chromatography. The procedure is based on estimates of two thermodynamic properties for each analyte (the differences in enthalpy and entropy associated with movements between the stationary and mobile phases) derived from data acquired experimentally in separations under isothermal conditions at temperatures spanning the range covered by the temperature programs in ten-degree increments. The columns used for this purpose were capillary columns containing polydimethylsiloxane-based stationary phases with three degrees of phenyl substitution (0%, 5%, and 50%). Predicted values were mostly within 1% of experimentally determined values, implying that the method is stable and precise.

  • 22.
    Ali Soomro, Razium
    et al.
    University of Sindh, Pakistan.
    Hallam, Keith Richard
    University of Bristol, UK.
    Hussain Ibupoto, Zafar
    University of Sindh, Pakistan.
    Tahira, Aneela
    University of Sindh, Pakistan.
    Tufail Hussain Sherazi, Syed
    University of Sindh, Pakistan.
    Juddin, Siraj
    University of Sindh, Pakistan.
    Jawaid, Sana
    University of Sindh, Pakistan.
    Willander, Magnus
    Linköping University, Department of Science and Technology, Physics and Electronics. Linköping University, Faculty of Science & Engineering.
    Glutaric Acid Assisted Fabrication of CuO Nanostructures and their Application in Development of Highly Sensitive Electrochemical Sensor System for Carbamates2016In: Electroanalysis, ISSN 1040-0397, E-ISSN 1521-4109, Vol. 28, no 7, 1634-1640 p.Article in journal (Refereed)
    Abstract [en]

    This work describes the fabrication of unique arrow head shaped CuO nanostructures using simple hydrothermal treatment method. The highly attractive features were obtained by the application of glutaric acid utilised simultaneous as template and functionalising agent. The functionalised nanostructures were known to possess excellent potential towards the electro-catalytic oxidation of carbofuran pesticide. The generated intense electrochemical signal with lower potential value enabled sensitive and selective determination of carbofuran up to 1 x 10(-3) mu M with wide sensing window in range of 0.01 to 0.16 mu M. The feasibility of the developed sensor system for the practical application was also studied by testing its potential in real sample extracts of various vegetables. The excellent recoveries demonstrated the analytical robustness of the developed sensor system. The sensor system utilises a new and simple approach towards sensitive determination of toxic pesticides reflecting its wide spectrum application in various fields.

  • 23.
    Ali Soomro, Razium
    et al.
    University of Bristol, England; University of Sindh, Pakistan.
    Hussain Ibupoto, Zafar
    Dr MA Kazi Institute Chemistry University of Sindh, Pakistan.
    Tufail Hussain Sirajuddin; Sherazi, Syed
    University of Sindh, Pakistan.
    Ishaq Abro, Muhammad
    Mehran University of Engn and Technology, Pakistan.
    Willander, Magnus
    Linköping University, Department of Science and Technology, Physics and Electronics. Linköping University, Faculty of Science & Engineering.
    Practice of diclofenac sodium for the hydrothermal growth of NiO nanostructures and their application for enzyme free glucose biosensor2016In: Microsystem Technologies: Micro- and Nanosystems Information Storage and Processing Systems, ISSN 0946-7076, E-ISSN 1432-1858, Vol. 22, no 10, 2549-2557 p.Article in journal (Refereed)
    Abstract [en]

    In this study diclofenac sodium (DFS), an analgesic drug has been employed as an effective template for the synthesis of NiO nanostructures. The NiO nanostructures were synthesised using low temperature hydrothermal growth method, both in the presence and absence of the DFS drug. The synthesised nanostructures were studied for their structural, compositional and electrochemical properties using scanning electron microscopy, X-ray diffraction and cyclic voltammetry. The synthesised nanostructures were then utilised for the modification of glassy carbon electrode which were then utilised for the electro-catalytic enzyme free glucose sensing in alkaline media. The competitive experiments suggested that although, both nanostructures possess excellent capability of glucose sensing, the NiO nanoflakes modified electrode was found to be twice as much as sensitive (2584 A mu A mM(-1) cm(-2)) as nanoflowers based electrode (1154 A mu A mM(-1) cm(-2)). The NiO nanoflakes based sensor further demonstrated excellent anti-interference potential in the presence of common interferents like uric acid, ascorbic acid and dopamine. In addition, the successful application NiO nanoflakes based sensor to determine real blood glucose concentration further suggest its feasibility for real sample analysis.

  • 24.
    Ali Soomro, Razium
    et al.
    University of Bristol, England; University of Sindh, Pakistan.
    Nafady, Ayman
    King Saud University, Saudi Arabia; Sohag University, Egypt.
    Hallam, Keith Richard
    University of Bristol, England.
    Jawaid, Sana
    University of Sindh, Pakistan.
    Al Enizi, Abdullah
    King Saud University, Saudi Arabia.
    Tufail Hussain Sherazi, Syed
    University of Sindh, Pakistan.
    Sirajuddin,
    Univ Sindh, Natl Ctr Excellence Analyt Chem, Jamshoro 76080, Pakistan.
    Ibupoto, Zafar Hussain
    Univ Sindh, Dr MA Kazi Inst Chem, Jamshoro 76080, Pakistan.
    Willander, Magnus
    Linköping University, Department of Science and Technology, Physics and Electronics. Linköping University, Faculty of Science & Engineering.
    Highly sensitive determination of atropine using cobalt oxide nanostructures: Influence of functional groups on the signal sensitivity2016In: Analytica Chimica Acta, ISSN 0003-2670, E-ISSN 1873-4324, Vol. 948, 30-39 p.Article in journal (Refereed)
    Abstract [en]

    This study describes sensitive determination of atropine using glassy carbon electrodes (GCE) modified with Co3O4 nanostructures. The as-synthesised nanostructures were grown using cysteine (CYS), glutathione (GSH) and histidine (HYS) as effective templates under hydrothermal action. The obtained morphologies revealed interesting structural features, including both cavity-based and flower-shaped structures. The as-synthesised morphologies were noted to actively participate in electro-catalysis of atropine (AT) drug where GSH-assisted structures exhibited the best signal response in terms of current density and over-potential value. The study also discusses the influence of functional groups on the signal sensitivity of atropine electro-oxidation. The functionalisation was carried with the amino acids originally used as effective templates for the growth of Co3O4 nanostructures. The highest increment was obtained when GSH was used as the surface functionalising agent. The GSH-functionalised Co3O4-modified electrode was utilised for the electro-chemical sensing of AT in a concentration range of 0.01 -0.46 mu M. The developed sensor exhibited excellent working linearity (R-2 = 0.999) and signal sensitivity up to 0.001 mu M of AT. The noted high sensitivity of the sensor is associated with the synergy of superb surface architectures and favourable interaction facilitating the electron transfer kinetics for the electro-catalytic oxidation of AT. Significantly, the developed sensor demonstrated excellent working capability when used for AT detection in human urine samples with strong anti-interference potential against common co-existing species, such as glucose, fructose, cysteine, uric acid, dopamine and ascorbic acid. (C) 2016 Elsevier B.V. All rights reserved.

  • 25.
    Allard, Erik
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Physical and Analytical Chemistry, Analytical Chemistry.
    Metabolic Studies with Liquid Separation Coupled to Mass Spectrometry2009Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    Metabolism is the sum of all chemical processes with the purpose to maintain life, as well as enable reproduction, in a living organism. Through the study of metabolism, increased understanding of pharmacological mechanisms and diseases can be achieved. This thesis describes several ways of doing so, including targeted analysis of selected metabolites and investigations of systematic metabolic differences between selected groups through pattern recognition.

    A method for exploring metabolic patterns in urine samples after intake of coffee or tea was developed. The methodology was later used with the aim to find biomarkers for prostate cancer and urinary bladder cancer.

    Furthermore, a fully automated quantitative method was developed for concentration measurements of the double prodrug ximelagatran and its metabolites in pig liver. The method was then used to study the roll of active transporters in pig liver cells.

    Moreover, a fundamental study was conducted to investigate how monitoring of small, doubly charged analytes can improve the limit of detection and precision in a quantitative method.

    The techniques used for the experiments were liquid separation coupled to electrospray mass spectrometry. Extra efforts were made to make the separation and the ionization as compatible as possible to each other for increased quality of the collected data.

  • 26.
    Allard, Erik
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Physical and Analytical Chemistry.
    Bäckström, Daniel
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Physical and Analytical Chemistry.
    Danielsson, Rolf
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Physical and Analytical Chemistry.
    Sjöberg, Per J.R.
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Physical and Analytical Chemistry.
    Bergquist, Jonas
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Physical and Analytical Chemistry.
    Comparing capillary electrophoresis: mass spectrometry fingerprints of urine samples obtained after intake of coffee, tea, or water.2008In: Analytical Chemistry, ISSN 0003-2700, E-ISSN 1520-6882, Vol. 80, no 23, 8946-8955 p.Article in journal (Refereed)
    Abstract [en]

    Metabolomic fingerprinting is a growing strategy for characterizing complex biological samples without detailed prior knowledge about the metabolic system. A two-way analysis system with liquid separation and mass spectrometric detection provides detail-rich data suitable for such fingerprints. As a model study, human urine samples, obtained after intake of coffee, tea, or water, were analyzed with capillary electrophoresis electrospray ionization time-of-flight mass spectrometry (CE−ESI-TOF-MS). In-house-developed software (in Matlab) was utilized to manage and explore the large amount of data acquired (230 CE−MS runs, each with 50−100 million nonzero data points). After baseline and noise reduction, followed by suitable binning in time and m/z, the data sets comprised 9 and 14 million data points in negative and positive ESI mode, respectively. Finally, a signal threshold was applied, further reducing the number to about 100 000 data points per data set. A set of interactive exploratory tools, utilizing principal component analysis (PCA) and analysis of variance (ANOVA) results based on a general linear model, facilitated visual interpretation with score plots (for group assessment) and differential fingerprints (for “hot spot” detection). In the model study highly significant differences due to beverage intake were obtained among the 10 first principal components (p < 10−6 for two of the components in both ESI modes). Especially, the contrasts between “coffee” and “tea or water” indicated several “hot spots” with highly elevated intensities (e.g., for uncharged masses 93, 94, 109, 119, 123, 132, 148, 169, 178, 187, 190, and 193) suitable for further analysis, for example, with tandem MS.

  • 27.
    Alm, Erik
    et al.
    Stockholm University, Faculty of Science, Department of Analytical Chemistry.
    Bro, Rasmus
    Engelsen, Sören B.
    Karlberg, Bo
    Stockholm University, Faculty of Science, Department of Analytical Chemistry.
    Torgrip, Ralf J. O.
    Stockholm University, Faculty of Science, Department of Analytical Chemistry.
    Vibrational overtone combination spectroscopy (VOCSY)—a new way of using IR and NIR data2007In: Analytical and Bioanalytical Chemistry, ISSN 1618-2642, E-ISSN 1618-2650, Vol. 388, no 1, 179-188 p.Article in journal (Refereed)
    Abstract [en]

    This work explores a novel method for rearranging 1st order (one-way) infra-red (IR) and/or near infra-red (NIR) ordinary spectra into a representation suitable for multi-way modelling and analysis. The method is based on the fact that the fundamental IR absorption and the first, second, and consecutive overtones of NIR absorptions represent identical chemical information. It is therefore possible to rearrange these overtone regions of the vectors comprising an IR and NIR spectrum into a matrix where the fundamental, 1st, 2nd, and consecutive overtones of the spectrum are arranged as either rows or columns in a matrix, resulting in a true three-way tensor of data for several samples. This tensorization facilitates explorative analysis and modelling with multi-way methods, for example parallel factor analysis (PARAFAC), N-way partial least squares (N-PLS), and Tucker models. The vibrational overtone combination spectroscopy (VOCSY) arrangement is shown to benefit from the “order advantage”, producing more robust, stable, and interpretable models than, for example, the traditional PLS modelling method. The proposed method also opens the field of NIR for true peak decomposition—a feature unique to the method because the latent factors acquired using PARAFAC can represent pure spectral components whereas latent factors in principal component analysis (PCA) and PLS usually do not.

  • 28.
    Alm, Erik
    et al.
    Stockholm University, Faculty of Science, Department of Analytical Chemistry.
    Slagbrand, Tove
    Stockholm University, Faculty of Science, Department of Analytical Chemistry.
    Åberg, K. Magnus
    Stockholm University, Faculty of Science, Department of Analytical Chemistry.
    Wahlström, Erik
    AstraZeneca R&D Sodertalje, Safety Assessment, Mol Toxicol, S-15185 Sodertalje, Sweden .
    Gustafsson, Ingela
    AstraZeneca R&D Sodertalje, Safety Assessment, Mol Toxicol, S-15185 Sodertalje, Sweden .
    Lindberg, Johan
    AstraZeneca R&D Sodertalje, Safety Assessment, Mol Toxicol, S-15185 Sodertalje, Sweden .
    Automated annotation and quantification of metabolites in (1)H NMR data of biological origin2012In: Analytical and Bioanalytical Chemistry, ISSN 1618-2642, E-ISSN 1618-2650, Vol. 403, no 2, 443-455 p.Article in journal (Refereed)
    Abstract [en]

    In 1H NMR metabolomic datasets, there are often over a thousand peaks per spectrum, many of which change position drastically between samples. Automatic alignment, annotation, and quantification of all the metabolites of interest in such datasets have not been feasible. In this work we propose a fully automated annotation and quantification procedure which requires annotation of metabolites only in a single spectrum. The reference database built from that single spectrum can be used for any number of 1H NMR datasets with a similar matrix. The procedure is based on the generalized fuzzy Hough transform (GFHT) for alignment and on Principal-components analysis (PCA) for peak selection and quantification. We show that we can establish quantities of 21 metabolites in several 1H NMR datasets and that the procedure is extendable to include any number of metabolites that can be identified in a single spectrum. The procedure speeds up the quantification of previously known metabolites and also returns a table containing the intensities and locations of all the peaks that were found and aligned but not assigned to a known metabolite. This enables both biopattern analysis of known metabolites and data mining for new potential biomarkers among the unknowns.

  • 29.
    Alm, Erik
    et al.
    Stockholm University, Faculty of Science, Department of Analytical Chemistry.
    Torgrip, Ralf J. O.
    Stockholm University, Faculty of Science, Department of Analytical Chemistry.
    Åberg, K. Magnus
    Stockholm University, Faculty of Science, Department of Analytical Chemistry.
    Schuppe-Koistinen, Ina
    Lindberg, Johan
    Time-resolved biomarker discovery inH-NMR data using generalized fuzzy Hough transform alignment and parallel factor analysis2010In: Analytical and Bioanalytical Chemistry, ISSN 1618-2642, E-ISSN 1618-2650, Vol. 396, no 5, 1681-1689 p.Article in journal (Refereed)
    Abstract [en]

    This work addresses the subject of time-series analysis of comprehensive 1H-NMR data of biological origin. One of the problems with toxicological and efficacy studies is the confounding of correlation between the administered drug, its metabolites and the systemic changes in molecular dynamics, i.e., the flux of drug-related molecules correlates with the molecules of system regulation. This correlation poses a problem for biomarker mining since this confounding must be untangled in order to separate true biomarker molecules from dose-related molecules. One way of achieving this goal is to perform pharmacokinetic analysis. The difference in pharmacokinetic time profiles of different molecules can aid in the elucidation of the origin of the dynamics, this can even be achieved regardless of whether the identity of the molecule is known or not. This mode of analysis is the basis for metabonomic studies of toxicology and efficacy. One major problem concerning the analysis of 1H-NMR data generated from metabonomic studies is that of the peak positional variation and of peak overlap. These phenomena induce variance in the data, obscuring the true information content and are hence unwanted but hard to avoid. Here, we show that by using the generalized fuzzy Hough transform spectral alignment, variable selection, and parallel factor analysis, we can solve both the alignment and the confounding problem stated above. Using the outlined method, several different temporal concentration profiles can be resolved and the majority of the studied molecules and their respective fluxes can be attributed to these resolved kinetic profiles. The resolved time profiles hereby simplifies finding true biomarkers and bio-patterns for early detection of biological conditions as well as providing more detailed information about the studied biological system. The presented method represents a significant step forward in time-series analysis of biological 1H-NMR data as it provides almost full automation of the whole data analysis process and is able to analyze over 800 unique features per sample. The method is demonstrated using a 1H-NMR rat urine dataset from a toxicology study and is compared with a classical approach: COW alignment followed by bucketing.

  • 30.
    Alm, Erik
    et al.
    Stockholm University, Faculty of Science, Department of Analytical Chemistry.
    Torgrip, Ralf J. O.
    Åberg, K. Magnus
    Stockholm University, Faculty of Science, Department of Analytical Chemistry.
    Schuppe-Koistinen, Ina
    Lindberg, Johan
    A solution to the 1D NMR alignment problem using an extended generalized fuzzy Hough transform and mode support2009In: Analytical and Bioanalytical Chemistry, ISSN 1618-2642, E-ISSN 1618-2650, Vol. 395, no 1, 213-223 p.Article in journal (Refereed)
    Abstract [en]

    This paper approaches the problem of intersample peak correspondence in the context of later applying statistical data analysis techniques to 1D 1H-nuclear magnetic resonance (NMR) data. Any data analysis methodology will fail to produce meaningful results if the analyzed data table is not synchronized, i.e., each analyzed variable frequency (Hz) does not originate from the same chemical source throughout the entire dataset. This is typically the case when dealing with NMR data from biological samples. In this paper, we present a new state of the art for solving this problem using the generalized fuzzy Hough transform (GFHT). This paper describes significant improvements since the method was introduced for NMR datasets of plasma in Csenki et al. (Anal Bioanal Chem 389:875-885, 15) and is now capable of synchronizing peaks from more complex datasets such as urine as well as plasma data. We present a novel way of globally modeling peak shifts using principal component analysis, a new algorithm for calculating the transform and an effective peak detection algorithm. The algorithm is applied to two real metabonomic 1H-NMR datasets and the properties of the method are compared to bucketing. We implicitly prove that GFHT establishes the objectively true correspondence. Desirable features of the GFHT are: (1) intersample peak correspondence even if peaks change order on the frequency axis and (2) the method is symmetric with respect to the samples.

  • 31.
    Alm, Johanna
    Linköping University, Department of Physics, Chemistry and Biology.
    Method development for identification of N-linked glycans by high performance anion exchange chromatography with pulsed amperometric detection and time of flight mass spectrometry2011Independent thesis Basic level (university diploma), 10,5 credits / 16 HE creditsStudent thesis
    Abstract [en]

    In the biopharmaceutical industry, identification of glycans in a glycoprotein is a regulatory requirement and is a part of the characterization of the protein. Glycans are constructed of several monosaccharides linked together. N-linked glycans, which have been studied in this project, are attached to the nitrogen atom in asparagine.

    A method for separating N-linked glycans by high performance anion exchange chromatography had already been developed at the department. To develop a method for identification of the N-glycans by mass spectrometry, a desalting method on porous graphitic carbon (PGC) columns was used and optimized resulting in the eluents A (0,05% TFA in ACN:water 5:95 v/v) and B (0,05% TFA in ACN:water 50:50 v/v). Also the sample introduction on the mass spectrometer was optimized and resulted in a sensitive on-line liquid chromatography mass spectrometry (LC-MS) approach which gave mass spectrometric peaks with high signal to noise ratios and with high mass accuracy.

    The developed procedure was then successfully used on glycans cleaved from a glycoprotein separated by high performance anion exchange chromatography with pulsed amperometric detector.

     

  • 32.
    Altun, Zeki
    Karlstad University, Faculty of Technology and Science, Department of Chemistry and Biomedical Sciences.
    New Techniques for Sample Preparation in Analytical Chemistry: Microextraction in Packed Syringe (MEPS) and Methacrylate Based Monolithic Pipette Tips2008Doctoral thesis, comprehensive summary (Other scientific)
    Abstract [en]

    Sample preparation is often a bottleneck in systems for chemical analysis. The aim of this work was to investigate and develop new techniques to address some of the shortcomings of current sample preparation methods. The goal has been to provide full automation, on-line coupling to detection systems, short sample preparation times and high-throughput.

    In this work a new technique for sample preparation that can be connected on-line to liquid chromatography (LC) and gas chromatography (GC) has been developed. Microextraction in packed syringe (MEPS) is a new solid-phase extraction (SPE) technique that is miniaturized and can be fully automated. In MEPS approximately 1 mg of sorbent material is inserted into a gas tight syringe (100-250 μL) as a plug. Sample preparation takes place on the packed bed. Evaluation of the technique was done by the determination of local anaesthetics in human plasma samples using MEPS on-line with LC and tandem mass spectrometry (MS-MS). MEPS connected to an autosampler was fully automated and clean-up of the samples took about one minute. In addition, in the case of plasma samples the same plug of sorbent could be used for about 100 extractions before it was discarded.

    A further aim of this work was to increase sample preparation throughput. To do that disposable pipette tips were packed with a plug of porous polymer monoliths as sample adsorbent and were then used in connection with 96-well plates and LC-MS-MS. The evaluation of the methods was done by the analysis of local anaesthetics lidocaine and ropivacaine, and anti-cancer drug roscovitine in plasma samples. When roscovitine and lidocaine in human plasma and water samples were used as model substances, a 96-plate was handled in about two minutes. Further, disposable pipette tips may be produced at low cost and because they are used only once, carry-over is eliminated.

  • 33.
    Altun, Zeki
    et al.
    Karlstad University, Faculty of Technology and Science, Department of Chemistry and Biomedical Sciences.
    Andersson, Lars I.
    AstraZeneca R&D Södertälje, DMPK & BAC, Södertälje, Sweden.
    Blomberg, Lars G.
    Karlstad University, Faculty of Technology and Science, Department of Chemistry and Biomedical Sciences.
    Abdel-Rehim, Mohamed
    Karlstad University, Division for Business and Economics.
    Some Factors Affecting the Performance of Microextraction in Packed Syringe (MEPS)Manuscript (Other academic)
  • 34.
    Alvarez, Laura
    et al.
    Umeå University, Faculty of Medicine, Molecular Infection Medicine Sweden (MIMS). Umeå University, Faculty of Medicine, Department of Molecular Biology (Faculty of Medicine). Umeå University, Faculty of Medicine, Umeå Centre for Microbial Research (UCMR).
    Hernandez, Sara B
    Umeå University, Faculty of Medicine, Molecular Infection Medicine Sweden (MIMS). Umeå University, Faculty of Medicine, Department of Molecular Biology (Faculty of Medicine). Umeå University, Faculty of Medicine, Umeå Centre for Microbial Research (UCMR).
    de Pedro, Miguel A
    Cava, Felipe
    Umeå University, Faculty of Medicine, Molecular Infection Medicine Sweden (MIMS). Umeå University, Faculty of Medicine, Department of Molecular Biology (Faculty of Medicine). Umeå University, Faculty of Medicine, Umeå Centre for Microbial Research (UCMR).
    Ultra-Sensitive, High-Resolution Liquid Chromatography Methods for the High-Throughput Quantitative Analysis of Bacterial Cell Wall Chemistry and Structure2016In: Bacterial Cell Wall Homeostasis: Methods and Protocols / [ed] Hee-Jeon Hong, New York: Springer Science+Business Media B.V., 2016, Vol. 1440, 11-27 p.Chapter in book (Refereed)
    Abstract [en]

    High-performance liquid chromatography (HPLC) analysis has been critical for determining the structural and chemical complexity of the cell wall. However this method is very time consuming in terms of sample preparation and chromatographic separation. Here we describe (1) optimized methods for peptidoglycan isolation from both Gram-negative and Gram-positive bacteria that dramatically reduce the sample preparation time, and (2) the application of the fast and highly efficient ultra-performance liquid chromatography (UPLC) technology to muropeptide separation and quantification. The advances in both analytical instrumentation and stationary-phase chemistry have allowed for evolved protocols which cut run time from hours (2-3 h) to minutes (10-20 min), and sample demands by at least one order of magnitude. Furthermore, development of methods based on organic solvents permits in-line mass spectrometry (MS) of the UPLC-resolved muropeptides. Application of these technologies to high-throughput analysis will expedite the better understanding of the cell wall biology.

  • 35.
    Amelina, Hanna
    et al.
    Stockholm University, Faculty of Science, Department of Biochemistry and Biophysics.
    Sjodin, Marcus O. D.
    Bergquist, Jonas
    Cristobal, Susana
    Stockholm University, Faculty of Science, Department of Biochemistry and Biophysics.
    Quantitative subproteomic analysis of age-related changes in mouse liver peroxisomes by iTRAQ LC-MS/MS2011In: Journal of chromatography. B, ISSN 1570-0232, E-ISSN 1873-376X, Vol. 879, no 30, 3393-3400 p.Article in journal (Refereed)
    Abstract [en]

    Aging is a complex multifactorial phenomenon, which is believed to result from the accumulation of cellular damage to biological macromolecules. Peroxisomes recently emerged as another important source of reactive oxygen species (ROS) production in addition to mitochondria. However, the role of these organelles in the process of aging is still not clear. The aim of this study was to characterize the changes in protein expression profiles of young (10 weeks old) versus old (18 months old) mouse liver peroxisome-enriched fractions. We have applied shotgun proteomic approach based on liquid chromatography and tandem mass spectrometry (LC-MS/MS) combined with iTRAQ (isobaric tags for relative and absolute quantitation) labeling that allows comparative quantitative multiplex analysis. Our analysis led to identification and quantification of 150 proteins, 8 out of which were differentially expressed between two age groups at a statistically significant level (p < 0.05), with folds ranging from 1.2 to 4.1. These proteins involved in peroxisornal beta-oxidation, detoxification of xenobiotics and production of ROS. Noteworthy, differences in liver proteome have been observed between as well as within different age groups. In conclusion, our subproteomic quantitative study suggests that mouse liver proteome is sufficiently maintained until certain age.

  • 36.
    Amelina, Hanna
    et al.
    Stockholm University, Faculty of Science, Department of Biochemistry and Biophysics.
    Sjödin, Marcus O. D.
    Bergquist, Jonas
    Cristobal, Susana
    Stockholm University, Faculty of Science, Department of Biochemistry and Biophysics.
    Quantitative subproteomic analysis of age-related changes in mouse liver peroxisomes by iTRAQ LC-MS/MSIn: Journal of chromatography. B, ISSN 1570-0232, E-ISSN 1873-376XArticle in journal (Refereed)
  • 37.
    Amini, Ahmad
    Uppsala University, Disciplinary Domain of Medicine and Pharmacy, Faculty of Pharmacy, Department of Medicinal Chemistry, Analytical Pharmaceutical Chemistry.
    Double-injection capillary electrophoresis for the identification of analytes2014In: Electrophoresis, ISSN 0173-0835, E-ISSN 1522-2683, Vol. 35, no 20, 2915-2921 p.Article in journal (Refereed)
    Abstract [en]

    This paper presents a new approach for identifying analytes by CE. The compound to be identified is analyzed together with the corresponding reference standard during a double injection capillary electrophoretic run. The inter-plug distance is regulated by applying an electrical field over the capillary for a predetermined time period (tPE). The migration time of an analyte being exposed to the partial electrophoresis was calculated from the partial migration time (tmig(p)) as described in this paper. The identification is based on the closeness of agreement between the calculated migration time (tmig(c)) and observed migration time (tmig) of the reference standard. The validity of the derived equations was checked by analyzing several substances such as caffeine, melamine, acetyl salicylic acid, paracetamol, ibuprofen, metoprolol, naproxen, somatropin, several insulin analogs, as well as different pharmaceutical and natural products. The migration time ratios for the identified solutes varied between 0.996 and 1.006 (i.e., 1.001 ± 0.005), indicating good agreement between the observed and calculated migration times.

  • 38.
    Amini, Ahmad
    Uppsala University, Disciplinary Domain of Medicine and Pharmacy, Faculty of Pharmacy, Department of Medicinal Chemistry, Analytical Pharmaceutical Chemistry.
    Identification of ε-caprolactam, melamine and urea in polyvinylpyrrolidone powders by micellar electrokinetic chromatography2014In: Journal of Pharmaceutical and Biomedical Analysis, ISSN 0731-7085, E-ISSN 1873-264X, Vol. 91, 12-16 p.Article in journal (Refereed)
    Abstract [en]

    A sodium dodecyl sulfate micellar electrokinetic chromatography (SDS-MEKC) method for the simultaneous separation and identification of ɛ-caprolactam, melamine and urea deliberately added to polyvinylpyrrolidone (povidone) products has been developed. All samples to be analyzed contained paracetamol as an internal marker (IM). The optimized separations were performed in 50 mM phosphate buffer (pH 7.0) containing 2% (w/v) sodium dodecyl sulfate (SDS) in fused silica capillaries with UV absorption detection at 200 nm. The method was validated with respect to repeatability and intermediate precision, selectivity and robustness with satisfactory results. The relative migration times (RMT) were found to be between 0.03% and 0.13% for intra-day precision and between 0.50% and 0.60% for inter-day precision in four days. The detection limits were determined to be 1.3 (11.5 μM), 0.4 (3.5 μM) and 41 μg/ml (0.4 mM) for ɛ-caprolactam, melamine and urea, respectively.

  • 39.
    Amini, Ahmad
    Uppsala University, Disciplinary Domain of Medicine and Pharmacy, Faculty of Pharmacy, Department of Medicinal Chemistry, Analytical Pharmaceutical Chemistry.
    Analysis of Caffeine in Dietary Products by Multiple Injection Capillary Electrophoresis2012In: Caffeine: Chemistry, Analysis, Function and Effects / [ed] Victor R Preedy, London: Royal Society of Chemistry, 2012, 154-178 p.Chapter in book (Refereed)
  • 40.
    Amini, Ahmad
    Uppsala University, Disciplinary Domain of Medicine and Pharmacy, Faculty of Pharmacy, Department of Medicinal Chemistry, Analytical Pharmaceutical Chemistry.
    Identification of Ɛ-Caprolactam and Melamine in Polyvinyl- Pyrrolidone Powder by Double Injection Micellar Elektrokinetic Chromatography2015In: Pharmaceutica analytica acta, ISSN 2153-2435, Vol. 6, no 11, 1000442Article in journal (Refereed)
    Abstract [en]

    A double-injection micellar electrokinetic chromatography (DIMEKC) method for the identification of Ɛ- caprolactam andmelamine deliberately added to povidone (polyvinylpyrrolidone) products has been developed. The separations were performedin 89 mM phosphate buffer (pH 7.4) containing 52 mM sodium dodecyl sulfate (SDS) in fused silica capillaries with UV absorptiondetection at 200 nm. The identification relied on the agreement between the calculated migration time (t mig(c) ) of the analytes andthe migration time (t mig ) of their corresponding reference standards being analysed simultaneously within a double injection run.The migration time of the analytes was calculated from the partial migration times (t mig(p) ) as described in this paper. The migrationtime ratios (t mig(c) / t mig ) varied

  • 41.
    Amini, Ahmad
    et al.
    Uppsala University, Disciplinary Domain of Medicine and Pharmacy, Faculty of Pharmacy, Department of Medicinal Chemistry, Analytical Pharmaceutical Chemistry.
    Rundlöf, Torgny
    Rönnquist, Kerstin
    Tydén, Monica
    Turunen, Taina
    Korhola, Paula
    Anette, Perolari
    A protocol for the quality assessment of illegally distributed human growth hormones with respect to identity, purity, endotoxin level and microorganism content2015In: Analytical Methods, ISSN 1759-9660, E-ISSN 1759-9679, Vol. 7, no 20, 8857-8864 p.Article in journal (Refereed)
    Abstract [en]

    Different methods based on MALDI-TOF-MS and double injection capillary zone electrophoresis (DICZE) were used for the identification and purity determination of somatropin in illegally distributed products. During the past few years, more than 200 products suspected to contain somatropin have been analysed. Some of the samples were also subjected to control microorganisms and endotoxins. The identification of somatropin was carried out by peptide mapping using trypsin as the proteolytic enzyme. A double chain peptide cross-linked via a disulfide bond was used as the signature peptide. Capillary electrophoresis in double injection mode was applied to both identification and purity determination of the samples. The identification was based on the comparison between the observed migration time of the reference standard and the calculated migration time of the analyte, being present in the second injection plug. The DICZE provides electrophoretic fingerprints of intact somatropin and the related proteins which facilitate the identification. In addition, some of these samples revealed the presence of microorganisms as well as a high level of endotoxins. Taken together, the doubtful quality of the analysed samples and the microbiological findings represent a serious threat for the consumers and public health.

  • 42.
    Amini, Nahid
    Stockholm University, Faculty of Science, Department of Analytical Chemistry.
    Novel Solid Phase Extraction and Mass Spectrometry Approaches to Multicomponent Analyses in Complex Matrices2010Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    Analysis of compounds present in complex matrices is always a challenge, which can be partly overcome by applying various sample preparation techniques prior to detection. Ideally, the extraction techniques should be as selective as possible, to minimize the concentration of interfering substances. In addition, results can be improved by efficient chromatographic separation of the sample components. The elimination of interfering substances is especially important when utilizing mass spectrometry (MS) as a detection technique since they influence the ionization yields. It is also important to optimize ionization methods in order to minimize detection limits.

    In the work this thesis is based upon, selective solid phase extraction (SPE) materials, a restricted access material (RAM) and graphitized carbon black (GCB) were employed for clean up and/or pre-concentration of analytes in plasma, urine and agricultural drainage water prior to liquid chromatography/mass spectrometry (LC/MS). Two SPE formats, in which GCB was incorporated in µ-traps and disks, were developed for cleaning up small and large volume samples, respectively. In addition, techniques based on use of sub-2 µm C18 particles at elevated temperatures and a linear ion trap (LIT) mass spectrometer were developed to improve the efficiency of LC separation and sensitivity of detection of 6-formylindolo[3,2-b]carbazole (FICZ) metabolites in human urine.

    It was also found that GCB can serve not only as a SPE sorbent, but also as a valuable surface for surface-assisted laser desorption ionization (SALDI) of small molecules. The dual functionality of GCB was utilized in a combined screening-identification/quantification procedure for fast elimination of negative samples. This may be particularly useful when processing large numbers of samples. SALDI analyses of small molecules was further investigated and improved by employing two kinds of new surfaces: oxidized GCB nanoparticles and silicon nitride.

  • 43.
    Amini, Nahid
    et al.
    Stockholm University, Faculty of Science, Department of Analytical Chemistry.
    Shariatgorji, Mohammadreza
    Stockholm University, Faculty of Science, Department of Analytical Chemistry.
    Crescenzi, Carlo
    Stockholm University, Faculty of Science, Department of Analytical Chemistry.
    Thorsen, Gunnar
    Stockholm University, Faculty of Science, Department of Analytical Chemistry.
    Screening and Quantification of Pesticides in Water Using a Dual-Function Graphitized Carbon Black Disk (Addition/Correction)2011In: Analytical Chemistry, ISSN 0003-2700, E-ISSN 1520-6882, Vol. 83, 631-631 p.Article in journal (Refereed)
  • 44.
    Amini, Nahid
    et al.
    Stockholm University, Faculty of Science, Department of Analytical Chemistry.
    Shariatgorji, Mohammadreza
    Stockholm University, Faculty of Science, Department of Analytical Chemistry.
    Crescenzi, Carlo
    Thorsén, Gunnar
    Stockholm University, Faculty of Science, Department of Analytical Chemistry.
    Screening and Quantification of Pesticides in Water Using a Dual-Function Graphitized Carbon Black Disk2010In: Analytical Chemistry, ISSN 0003-2700, E-ISSN 1520-6882, Vol. 82, no 1, 290-296 p.Article in journal (Refereed)
    Abstract [en]

    A simple platform for combining solid phase extraction (SPE) and surface-assisted laser desorption ionization mass spectrometry (SALDI-MS) of extracted analytes, using disks prepared by embedding graphitized carbon black (GCB-4) particles in a network of polytetrafluoroethylene (PTFE), is presented. The system provides a convenient approach for rapid SALDI-MS screening of substances in aqueous samples, which can be followed by robust quantitative and/or structural analyses by liquid chromatography (LC)/MS/MS of positive samples. The extraction discs are easily transferred between gaskets where the sample extraction and desorption of selected samples is performed and the mass spectrometer. The SPE and SALDI properties of the new GCB-4 disc have been characterized for 15 pesticides with varying chemical properties, and the screening strategy has been applied to the analysis of pesticides in agricultural drainage water. Atrazine and atrazine-desethyl-2-hydroxy were detected in the sampled water by SALDI-MS screening and subsequently confirmed and quantified using LC/MS/MS.

  • 45.
    Aminlashgari, Nina
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Polymer Technology.
    SALDI-MS Method Development for Analysis of Pharmaceuticals and Polymer Degradation Products2012Licentiate thesis, comprehensive summary (Other academic)
    Abstract [en]

    Surface assisted laser desorption ionization-mass spectrometry (SALDI-MS) was evaluated as a new tool for analysis of polymer degradation products. A SALDI method was developed enabling rapid analysis of low molecular mass polyesters and their degradation products. In addition, the possibility to utilize nanocomposite films as easy-to-handle surfaces for analysis of pharmaceutical compounds was investigated.

    Poly(ε-caprolactone) was used as a model compound for SALDI-MS method development. The signal-to-noise values obtained by SALDI-MS were 20 times higher compared to traditional matrix assisted laser desorption ionization-mass spectrometry (MALDI-MS) of the same samples with 2,5-dihydroxybenzoic acid as a matrix. Halloysite nanoclay and magnesium oxide showed best potential as surfaces and clean backgrounds in the low mass range were observed. The SALDI-MS method for the analysis of polyester degradation products was also verified by electrospray ionization-mass spectrometry (ESI-MS). An advantage over ESI-MS is the possibility to directly analyze degradation products in buffer solutions. Compared to gas chromatography-mass spectrometry (GC-MS) it is possible to analyze polar compounds and larger molecular mass ranges at the same time as  complicated extraction steps are avoided.

    The possibility to use nanocomposite films as surfaces instead of free nanoparticles was evaluated by solution casting of poly(lactide) (PLA) films with eight inorganic nanoparticles. The S/N values of the pharmaceutical compounds, acebutolol, propranolol and carbamazepine, analyzed on the nanocomposite surfaces were higher than the values obtained on the surface of plain PLA showing that the nanoparticles participated in the ionization/desorption process even when they are immobilized. Beside the ease of handling, the risk for instrument contamination is reduced when nanocomposites are used instead of free nanoparticles. The signal intensities depended on the type of drug, type and concentration of nanoparticle. PLA with 10 % titanium oxide or 10 % silicon nitride functioned best as SALDI-MS surfaces.

  • 46.
    Aminlashgari, Nina
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Polymer Technology.
    Hakkarainen, Minna
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Polymer Technology.
    Surface Assisted Laser Desorption Ionization-Mass Spectrometry (SALDI-MS) for Analysis of Polyester Degradation Products2012In: Journal of the American Society for Mass Spectrometry, ISSN 1044-0305, E-ISSN 1879-1123, Vol. 23, no 6, 1071-1076 p.Article in journal (Refereed)
    Abstract [en]

    Novel surface assisted laser desorption ionization-mass spectrometry (SALDI-MS) method was developed for rapid analysis of low molecular mass polyesters and their degradation products by laser desorption ionization-mass spectrometry. Three polycaprolactone materials were analyzed by the developed method before and after hydrolytic degradation. The signal-to-noise values obtained by SALDI-MS were 20-100 times higher compared with the ones obtained by using traditional MALDI-MS matrices. A clean background at low mass range and higher resolution was obtained by SALDI-MS. Different nanoparticle, cationizing agent, and solvent combinations were evaluated. Halloysite nanoclay and magnesium hydroxide showed the best potential as SALDI surfaces. The SALDI-MS spectrum of the polyester hydrolysis products was verified by ESI-MS. The developed SALDI-MS method possesses several advantages over existing methods for similar analyses.

  • 47. Aminlashgari, Nina
    et al.
    Shariatgorji, Mohammadreza
    Stockholm University, Faculty of Science, Department of Analytical Chemistry.
    Ilag, Leopold L.
    Stockholm University, Faculty of Science, Department of Analytical Chemistry.
    Hakkarainen, Minna
    Nanocomposites as novel surfaces for laser desorption ionization mass spectrometry2011In: Analytical Methods, ISSN 1759-9660, Vol. 3, no 1, 192-197 p.Article in journal (Refereed)
    Abstract [en]

    The possibility to utilize nanocomposite films as easy-to-handle surfaces for surface assisted laser desorption ionization-mass spectrometry (SALDI-MS) of small molecules, such as pharmaceutical compounds, was evaluated. The signal-to-noise values of acebutolol, propranolol and carbamazepine obtained on the nanocomposite surfaces were higher than the values obtained on plain PLA surface showing that the nanoparticles participate in the ionization/desorption process even when they are immobilized in the polymer matrix. The advantages of nanocomposite films compared to the free nanoparticles used in earlier studies are the ease of handling and reduction of instrument contamination since the particles are immobilized into the polymer matrix. Eight inorganic nanoparticles, titanium dioxide, silicon dioxide, magnesium oxide, hydroxyapatite, montmorillonite nanoclay, halloysite nanoclay, silicon nitride and graphitized carbon black at different concentrations were solution casted to films with polylactide (PLA). There were large differences in signal intensities depending on the type of drug, type of nanoparticle and the concentration of nanoparticles. Polylactide with 10% titanium oxide or 10% silicon nitride functioned best as SALDI-MS surfaces. The limit of detection (LOD) for the study was ranging from 1.7 ppm up to 56.3 ppm and the signal to noise relative standard deviations for the surface containing 10% silicon nitride was approximately 20-30%. Scanning electron microscopy demonstrated in most cases a good distribution of the nanoparticles in the polymer matrix and contact angle measurements showed increasing hydrophobicity when the nanoparticle concentration was increased, which could influence the desorption and ionization. Overall, the results show that nanocomposite films have potential as surfaces for SALDI-MS analysis of small molecules.

  • 48.
    Aminlashgari, Nina
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Polymer Technology.
    Shariatgorji, Mohammadreza
    Department of Analytical Chemistry, Stockholm University, Stockholm, Sweden.
    Ilag, Leopold L.
    Department of Analytical Chemistry, Stockholm University, Stockholm, Sweden.
    Hakkarainen, Minna
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Polymer Technology.
    Nanocomposites as novel surfaces for laser desorption ionization mass spectrometry2011In: Analytical Methods, ISSN 1759-9660, Vol. 3, no 1, 192-197 p.Article in journal (Refereed)
    Abstract [en]

    The possibility to utilize nanocomposite films as easy-to-handle surfaces for surface assisted laser desorption ionization-mass spectrometry (SALDI-MS) of small molecules, such as pharmaceutical compounds, was evaluated. The signal-to-noise values of acebutolol, propranolol and carbamazepine obtained on the nanocomposite surfaces were higher than the values obtained on plain PLA surface showing that the nanoparticles participate in the ionization/desorption process even when they are immobilized in the polymer matrix. The advantages of nanocomposite films compared to the free nanoparticles used in earlier studies are the ease of handling and reduction of instrument contamination since the particles are immobilized into the polymer matrix. Eight inorganic nanoparticles, titanium dioxide, silicon dioxide, magnesium oxide, hydroxyapatite, montmorillonite nanoclay, halloysite nanoclay, silicon nitride and graphitized carbon black at different concentrations were solution casted to films with polylactide (PLA). There were large differences in signal intensities depending on the type of drug, type of nanoparticle and the concentration of nanoparticles. Polylactide with 10% titanium oxide or 10% silicon nitride functioned best as SALDI-MS surfaces. The limit of detection (LOD) for the study was ranging from 1.7 ppm up to 56.3 ppm and the signal to noise relative standard deviations for the surface containing 10% silicon nitride was approximately 20-30%. Scanning electron microscopy demonstrated in most cases a good distribution of the nanoparticles in the polymer matrix and contact angle measurements showed increasing hydrophobicity when the nanoparticle concentration was increased, which could influence the desorption and ionization. Overall, the results show that nanocomposite films have potential as surfaces for SALDI-MS analysis of small molecules.

  • 49.
    Amirkhani, A.
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry.
    Heldin, E.
    Markides, K.E.
    Bergquist, J.
    Quantitation of tryptophan, kynurenine and kynurenic acid in human plasma by capillary liquid chromatography - electrospray ionization tandem mass spectrometry2002In: J. of Chromatography B, no 780, 381-387 p.Article in journal (Refereed)
  • 50.
    Amirkhani, Ardeshir
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry, Analytical Chemistry.
    Development of Techniques and Methods for the Quantitative Analysis of Endogenous Substances by Microcolumn Liquid Chromatography Coupled to Mass Spectrometry2004Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    Liquid chromatography-mass spectrometry (LC-MS) is a powerful technique for the analysis of endogenous compounds. The introduction of electrospray ionization (ESI) as an interface between LC and MS has contributed strongly to a trend towards miniaturization of LC, due to the possibility to perform ESI at low flow rates. In this thesis, several aspects regarding the design of miniaturized LC systems and electrospray emitters were investigated. In addition miniaturized LC-ESI-MS have been used for the qualitative and quantitative analysis of endogenous polar compounds, peptides and protein digests.

    The performance of miniaturized LC-MS was compared using different electrospray emitter configurations. The results indicated that the efficiency of the LC system is rather independent of the configuration of the emitter.

    The lifetime of gold-coated fused silica electrospray emitters based on vapor deposited adhesion layers of titanium were investigated. The long lifetime of the emitter facilitates the use in LC-MS experiments, exemplified LC-MS by analysis of neuropeptides.

    The ESI voltage is shown to interfere with liquid chromatographic separations performed in packed porous graphitic carbon capillary column. This interference is ascribed to the presence of an electric field over the conductive column in absence of a ground point between the column and the ESI emitter.

    The solid supported enhanced microdialysis for analysis of neuropeptides were compared with conventional microdialysis. The difference between the two methodologies were evaluated by LC-MS analysis of the microdialysates. The solid supported method gave in general higher relative recoveries.

    Finally, a method of standard addition was developed to determine total level of tryptophan and two of its metabolites in human plasma by capillary LC-ESI tandem mass spectrometry. The method was applied in a clinical study of multiple scleroses patients treated with cytokines (IFN Beta 1a, 1b). The results show that the intervention effects the tryptophan metabolism.

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