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  • 1.
    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, p. 867-872Article 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.

  • 2.
    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, p. 381-387Article in journal (Refereed)
  • 3.
    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.

    List of papers
    1. Comparison between different sheathless electrospray emitter configurations regarding the performance of nanoscale liquid chromatography time-of-flight mass spectrometry analysis
    Open this publication in new window or tab >>Comparison between different sheathless electrospray emitter configurations regarding the performance of nanoscale liquid chromatography time-of-flight mass spectrometry analysis
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    2004 (English)In: Journal of Chromatography A, ISSN 0021-9673, E-ISSN 1873-3778, Vol. 1033, no 2, p. 257-266Article in journal (Refereed) Published
    Abstract [en]

    Four different sheathless electrospray ionization (ESI) configurations were investigated for a nano liquid chromatography (LC) system. The studied configurations were: a column with an integrated emitter, with the ESI potential applied before or after the column, and a column with separate emitter, with the ESI voltage applied at a union before the emitter or at the emitter tip. The results indicates that the efficiency of the LC system is rather independent of the configuration when using 95 μm i.d. columns, acetic mobile phase and standard peptides as a sample. Introduction of post column dead volume seems not to be a critical issue at least with flow rates down to 600 nl/min.

    Keyword
    Electrospray ionization, Band broadening, Principal component analysis, Instrumentation, Peptides
    National Category
    Chemical Sciences
    Identifiers
    urn:nbn:se:uu:diva-91889 (URN)10.1016/j.chroma.2004.01.063 (DOI)
    Available from: 2004-05-25 Created: 2004-05-25 Last updated: 2017-12-14Bibliographically approved
    2. Gold-coated fused-silica sheathless electrospray emitters based on vapor-deposited titanium adhesion layers
    Open this publication in new window or tab >>Gold-coated fused-silica sheathless electrospray emitters based on vapor-deposited titanium adhesion layers
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    2003 In: Rapid Communication Mass Spectrometry, Vol. 17, no 14, p. 1535-1540Article in journal (Refereed) Published
    Identifiers
    urn:nbn:se:uu:diva-91337 (URN)
    Available from: 2004-01-30 Created: 2004-01-30Bibliographically approved
    3. Interference of the electrospray voltage on chromatographic separations using porous graphitic carbon columns
    Open this publication in new window or tab >>Interference of the electrospray voltage on chromatographic separations using porous graphitic carbon columns
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    2004 (English)In: Journal of Mass Spectrometry, ISSN 1076-5174, E-ISSN 1096-9888, Vol. 39, no 2, p. 216-222Article in journal (Refereed) Published
    Abstract [en]

    The electrospray ionization (ESI) voltage is shown to interfere with liquid chromatographic separations performed with packed porous graphitic carbon (PGC) capillary columns. This interference is ascribed to the presence of an electric field over the conductive column in the absence of an earth point between the column and the ESI emitter. The current evolved alters the chromatographic behavior of the catecholamine metabolite 3-O-methyl-DOPA significantly, as both peak splitting and a dramatic decrease in the retention time were observed. Furthermore, the response from the mass spectrometer was decreased by 33% at the same time. A related compound, tyrosine, exhibited decreased retention times but no peak splitting, whereas no shifts in the retention times (or peak splitting) were seen for the less retained dopamine and noradrenaline. When the current through the PGC column was eliminated by the use of an earth point between the column and the ESI emitter, the chromatographic behavior of the column was found to return slowly to normal after hours of equilibration with 60 : 40 (v/v) methanol-ammonium formate buffer of pH 2.9. The behavior of the PGC column with and without the earth point was found to be highly reproducible during a period of 1 month. We propose that the effect of the ESI voltage on the chromatographic behavior of the PGC column is due to associated redox reactions affecting both the PGC particles and the analytes. It is concluded that (for analytical reasons), care should be taken to ensure that no current is flowing through the chromatographic system when interfacing PGC columns, and conducting parts in general, to ESI mass spectrometry.

    Keyword
    catecholamine, dopamine, electrochemistry, porous graphitic carbon, electrospray, mass spectrometry, liquid chromatography
    National Category
    Inorganic Chemistry
    Identifiers
    urn:nbn:se:uu:diva-91888 (URN)10.1002/jms.589 (DOI)
    Available from: 2004-05-25 Created: 2004-05-25 Last updated: 2017-12-14Bibliographically approved
    4. A feasibility study of solid supported enhanced microdialysis
    Open this publication in new window or tab >>A feasibility study of solid supported enhanced microdialysis
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    2004 (English)In: Analytical Chemistry, ISSN 0003-2700, E-ISSN 1520-6882, Vol. 76, no 6, p. 1678-1682Article in journal (Refereed) Published
    Abstract [en]

    For the first time, a solid supported enhanced microdialysis methodology for analysis of neuropeptides is described. The microdialysis samples were, in this study, subsequently collected in fractions, dissolved from the solid particles, dried, and resolved in a formic acid buffer in order to make them suitable for capillary liquid chromatography-mass spectrometry. Different microdialysis flow profiles were evaluated where air-gapped continuous flow was considered most suitable for the solid supported microdialysis mode. Six endogenous neuropeptides were initially used to investigate the feasibility of this enhanced microdialysis methodology. The improved relative recovery obtained from the solid supported enhanced microdialysis was varying from no effect to 10 times higher as compared to ordinary microdialysis. The most efficient enrichment was obtained for luteinizing hormone releasing hormone, which was the largest but also the most hydrophilic of the peptides. In contrast, no significant difference in recovery was observed for Leu-enkephalin being the smallest and the most hydrophobic peptide tested. These results indicate an increased flux and selective uptake of hydrophilic peptides across the membrane and enrichment on the particles in solid supported microdialysis.

    National Category
    Natural Sciences
    Identifiers
    urn:nbn:se:uu:diva-93181 (URN)10.1021/ac035305l (DOI)15018567 (PubMedID)
    Available from: 2005-05-10 Created: 2005-05-10 Last updated: 2017-12-14Bibliographically approved
    5. Quantitation of tryptophan, kynurenine and kynurenic acid in human plasma by capillary liquid chromatography - electrospray
    Open this publication in new window or tab >>Quantitation of tryptophan, kynurenine and kynurenic acid in human plasma by capillary liquid chromatography - electrospray
    2002 In: Journal of Chromatography B, Vol. 780, no 2, p. 381-387Article in journal (Refereed) Published
    Identifiers
    urn:nbn:se:uu:diva-91340 (URN)
    Available from: 2004-01-30 Created: 2004-01-30 Last updated: 2011-03-21
    6. Beta-interferon effects the tryptophan metabolism in the plasma of multiple sclerosis patients
    Open this publication in new window or tab >>Beta-interferon effects the tryptophan metabolism in the plasma of multiple sclerosis patients
    Show others...
    Manuscript (Other academic)
    Identifiers
    urn:nbn:se:uu:diva-91341 (URN)
    Available from: 2004-01-30 Created: 2004-01-30 Last updated: 2011-03-21
  • 4.
    Bergquist, J.
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry.
    From molecule to man - using electrospray Fourier Transform ion cyclotron resonance mass spectrometry (ESI-FTICR-MS) in proteomics2003In: ISMAS Silver Jubilee Symposium on Mass Spectrometry, 2003Chapter in book (Other academic)
  • 5.
    Bergquist, J.
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry.
    FTICR mass spectrometry in proteomics2003In: Current Opinion in Molecular Therapeutics, no 5, p. 310-314Article in journal (Refereed)
  • 6.
    Bergquist, J.
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry.
    Ekman, R.
    The dynamics of the cell nucleus - Lymphocyte nuclei associated peptides studied by mass spectrometry and future peptidomic aspects2002In: Mass spectrometry and Hyphenated Techniques in Neuropeptide Research, John Wiley & Sons, N.Y. , 2002, Vol. Chapter 21, p. 519-553Chapter in book (Refereed)
  • 7.
    Bergquist, J.
    et al.
    ION PHYSICS. Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry.
    Palmblad, M.
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Materials Science.
    Wetterhall, M., Håkansson, P., Markides, K.E.
    Peptide mapping of proteins in human body fluids using electrospray ionisation Fourier transform ion cyclotron resonance mass spectrometry2002In: Mass. Spectrom. Reviews, no 21, p. 2-15Article in journal (Refereed)
  • 8.
    Bergquist, J.
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry.
    Sciubisz, A.
    Kaczor, A.
    Silberring, J.
    Catecholamines and methods for their identification and quantitation in biological tissues and fluids2002In: J. Neurosci. Meth., no 113, p. 1-13Article in journal (Refereed)
  • 9.
    Bergquist, J.
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry.
    Träskman-Bendz, L.
    Lindström, M.B.
    Ekman, R.
    Suicide-attempters having immunoglobulin G with affinity for dopamine in cerebrospinal fluid2002In: European Neuropsychopharmacology, no 12, p. 153-158Article in journal (Refereed)
  • 10.
    Bergström, Sara
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry, Analytical Chemistry.
    Integrated Micro-Analytical Tools for Life Science2005Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    Advances in life science require knowledge of active molecules in complex biological systems. These molecules are often only present for a certain time and at limited concentrations. Integrated micro-analytical tools for sampling, separation and mass spectrometric (MS) detection would meet these requests and are therefore continuously gaining interest. An on-line coupling of analytical functions provides shorter analysis time and less manual sample handling. In this thesis, improved compatibility of microdialysis sampling and multidimensional separations coupled to MS detection are developed and discussed.

    Microdialysis was used in vitro for determination of the non-protein bound fraction of the drug ropivacaine. The sampling unit was coupled on-line to capillary column liquid chromatography (LC) followed by ultraviolet or MS detection. For MS detection, the system was extended with a desalting step and an addition of internal standard. A method for MS screening of microdialysates, collected in vivo, was also developed. The method involved sampling and measurements of the chemical pattern of molecules that generally are ignored in clinical investigations. Chemometric tools were used to extract the relevant information and to compare samples from stimulated and control tissues.

    Complex samples often require separation in more than one dimension. On-line interfaces for sample transfer between LC and capillary electrophoresis (CE) were developed in soft poly(dimethylsiloxane) (PDMS). MS detection in the LC-CE system was optimised on frequent sampling of the CE peak or on high resolution in mass spectra using time-of-flight (TOF)MS or Fourier transform ion cyclotron resonance (FTICR)MS, respectively. Aspects on electrode positioning in the LC-CE interface led to development of an on-column CE electrode. A successful method for deactivation of the PDMS surface using a polyamine polymer was also developed. The systems were evaluated using peptides and proteins, molecules that are gaining increased attention in bioscience, and consequently also in chemical analysis.

    List of papers
    1. Determination of the free concentration of ropivacaine in plasma by packed capillary liquid chromatography: A comparison of ultrafiltration and microdialysis as sample preparation methods
    Open this publication in new window or tab >>Determination of the free concentration of ropivacaine in plasma by packed capillary liquid chromatography: A comparison of ultrafiltration and microdialysis as sample preparation methods
    2001 (English)In: Journal of Microcolumn Separations, ISSN 1040-7685, E-ISSN 1520-667X, Vol. 13, no 5, p. 197-201Article in journal (Refereed) Published
    Abstract [en]

    In this study, ultrafiltration and microdialysis have been compared as sample preparation methods to separate the free fraction of ropivacaine from the protein bound in 150 μL plasma. A liquid chromatographic system with packed capillary columns (0.2 mm internal diameter) was used to enhance sensitivity when analyzing the small sample volumes obtained after the ultrafiltration and the microdialysis. The microdialysis was performed with probes of our own construction, and to save analysis time, the microdialysis sampling was coupled on-line to the liquid chromatographic system. The reduction of back pressure in the microdialysis outlet tube and in the injector was found to be essential. The free fraction obtained with each method was equivalent: both gave a free fraction of 6%.

    Keyword
    microdialysis, ultrafiltration, free fraction, ropivacaine, capillary liquid chromatography
    National Category
    Analytical Chemistry
    Identifiers
    urn:nbn:se:uu:diva-93670 (URN)10.1002/mcs.1042 (DOI)
    Available from: 2005-10-28 Created: 2005-10-28 Last updated: 2017-12-14Bibliographically approved
    2. On-line coupling of microdialysis to packed capillary column liquid chromatography-tandem mass spectrometry demonstrated by measurement of free concentrations of ropivacaine and metabolite from spiked plasma samples
    Open this publication in new window or tab >>On-line coupling of microdialysis to packed capillary column liquid chromatography-tandem mass spectrometry demonstrated by measurement of free concentrations of ropivacaine and metabolite from spiked plasma samples
    2002 (English)In: Journal of chromatography. B, ISSN 1570-0232, E-ISSN 1873-376X, Vol. 775, no 1, p. 79-87Article in journal (Refereed) Published
    Abstract [en]

    An on-line coupling of microdialysis to a packed capillary column switching liquid chromatographic system (0.2 mm I.D.) and mass spectrometric detection was developed. The microdialysates were collected in the loop of the first of three valves, coupled in direct series. A deuterated internal standard was added on-line by the middle valve and the third valve operated both a pre-column, for desalting of the physiological buffer used in the sampling procedure, and a separation column. The on-line system was used to study free concentrations of ropivacaine and its metabolite (PPX) in human plasma samples. The analytes were detected by electrospray ionization in a tandem mass spectrometer operating in multiple reaction monitoring mode. The free fractions of ropivacaine (200 nM total concentration) and PPX (20 nM total concentration) in spiked plasma samples were 12±3 and 47±5% (±standard deviation for day-to-day variations, n=3), respectively.

    National Category
    Analytical Chemistry
    Identifiers
    urn:nbn:se:uu:diva-93671 (URN)10.1016/S1570-0232(02)00280-5 (DOI)
    Available from: 2005-10-28 Created: 2005-10-28 Last updated: 2017-12-14Bibliographically approved
    3. Screening of microdialysates using on-line desalting and mass spectrometric detection
    Open this publication in new window or tab >>Screening of microdialysates using on-line desalting and mass spectrometric detection
    Show others...
    In: J. Chromatogr. AArticle in journal (Refereed) Submitted
    Identifiers
    urn:nbn:se:uu:diva-93672 (URN)
    Available from: 2005-10-28 Created: 2005-10-28Bibliographically approved
    4. On-column polymer-imbedded graphite inlet electrode for capillary electrophoresis coupled on-line with flow injection analysis in a poly(dimethylsiloxane) interface
    Open this publication in new window or tab >>On-column polymer-imbedded graphite inlet electrode for capillary electrophoresis coupled on-line with flow injection analysis in a poly(dimethylsiloxane) interface
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    2003 (English)In: Electrophoresis, ISSN 0173-0835, E-ISSN 1522-2683, Vol. 24, no 11, p. 1723-1729Article in journal (Refereed) Published
    Abstract [en]

    A method for coupling an electrophoretic driven separation to a liquid flow, using conventional fused-silica capillaries and a soft polymeric interface is presented. A novel design of the electrode providing high voltage to the electrophoretic separation was also developed. The electrode consisted of a conductive polyimide/graphite imbedded coating immobilized onto the capillary electrophoresis (CE) column inlet. This integrated electrode gave the same separation performance as a commonly used platinum electrode. The on-column electrode also showed good electrochemical stability in chronoamperometric experiments. In addition, with this electrode design, the electrode position relative to the inlet end of the CE column will always be constant and well defined. The on-line flow injection analysis (FIA)-CE system was used with electrospray ionization (ESI)-time of flight (TOF)-mass spectrometry detection. The preparation of the PDMS (poly(dimethylsiloxane)) interface for FIA-CE is described in detail and used for initial tests of the on-column polymer-imbedded graphite inlet electrode. In this interface, a pressure-driven liquid flow, a make up CE electrolyte and a CE column inlet meet in a two-level cross (95 μm ID) in the PDMS structure, enabling independent flow characterization.

    Keyword
    Capillary electrophoresis, Flow injection, Hyphenation, On-column electrode, Poly(dimethylsiloxane)
    National Category
    Chemical Sciences
    Identifiers
    urn:nbn:se:uu:diva-94267 (URN)10.1002/elps.200305362 (DOI)
    Available from: 2006-04-07 Created: 2006-04-07 Last updated: 2017-12-14Bibliographically approved
    5. Development of a poly(dimethylsiloxane) interface for on-line capillary column liquid chromatography-capillary electrophoresis coupled to sheathless electrospray ionization time-of-flight mass spectrometry
    Open this publication in new window or tab >>Development of a poly(dimethylsiloxane) interface for on-line capillary column liquid chromatography-capillary electrophoresis coupled to sheathless electrospray ionization time-of-flight mass spectrometry
    2003 In: Anal. Chem., ISSN 0003-2700, Vol. 75, no 20, p. 5461-5467Article in journal (Refereed) Published
    Identifiers
    urn:nbn:se:uu:diva-93674 (URN)
    Available from: 2005-10-28 Created: 2005-10-28Bibliographically approved
    6. Polyamine deactivation of integrated poly(dimethylsiloxane) structures investigated by radionuclide imaging and capillary electrophoresis experiments
    Open this publication in new window or tab >>Polyamine deactivation of integrated poly(dimethylsiloxane) structures investigated by radionuclide imaging and capillary electrophoresis experiments
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    2005 (English)In: Analytical Chemistry, ISSN 0003-2700, E-ISSN 1520-6882, Vol. 77, no 3, p. 938-942Article in journal (Refereed) Published
    Abstract [en]

    The poly(dimethylsiloxane) (PDMS) material provides a number of advantageous features, such as flexibility, elasticity, and transparency, making it useful in integrated analytical systems. Hard fused-silica capillary structures and soft PDMS channels can easily be combined by a tight fit, which offers many alternatives for structure combinations. PDMS and fused silica are in different ways prone to adsorption of low levels of organic compounds. The need for modification of the inner wall surface of PDMS channels may often be necessary, and in this paper, we describe an easy and effective method using the amine-containing polymer PolyE-323 to deactivate both fused-silica and PDMS surfaces. The adsorption of selected peptides to untreated surfaces was compared to PolyE-323-modified surfaces, using both radionuclide imaging and capillary electrophoresis experiments. The polyamine modification displayed a substantially reduced adsorption of three hydrophobic test peptides compared to the native PDMS surface. Filling and storage of aqueous solution were also possible in PolyE-323-modified PDMS channels. In addition, hybrid microstructures of fused silica and PDMS could simultaneously be deactivated in one simple coating procedure.

    National Category
    Chemical Sciences
    Identifiers
    urn:nbn:se:uu:diva-93675 (URN)10.1021/ac0492618 (DOI)
    Available from: 2005-10-28 Created: 2005-10-28 Last updated: 2017-12-14Bibliographically approved
    7. A simplified multidimensional approach for analysis of complex biological samples: on-line LC-CE-MS
    Open this publication in new window or tab >>A simplified multidimensional approach for analysis of complex biological samples: on-line LC-CE-MS
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    2006 (English)In: The Analyst, ISSN 0003-2654, E-ISSN 1364-5528, Vol. 131, no 7, p. 791-798Article in journal (Refereed) Published
    Abstract [en]

    Information on protein expression, disease biomarkers or surrogate markers and genetic disorders can nowadays be achieved from analysis of complex biological samples by liquid separation coupled to mass spectrometric (MS) detection. This paper describes fast multidimensional separation by on-line liquid chromatography (LC) and capillary electrophoresis (CE), followed by electrospray ionization (ESI) Fourier transform ion cyclotron resonance (FTICR) MS detection. This detector provides ultrahigh resolution of the detected ions, mass accuracy at the ppm-level and high sensitivity. Most of the challenge of this system lies in the development of a new interface for the on-line coupling of LC to CE. The interface developed in poly(dimethylsiloxane) provides a RSD for injection repeatability of <3.5% and surface control for unspecific binding by deactivation with a cationic polymer, PolyE-323. We have evaluated the interface, as well as the overall system, with respect to robustness and deconvolution ability. Sequence coverage for bovine serum albumin (BSA) of 93% showed a high recovery of sample in the different transfer steps through the system. The detection limit for identification is 277 ng mL−1 (or 280 nM) on average for peptides. In the future, we expect LC-CE-MS to be a novel strategy for elucidating the chemistry of biological matrices.

    National Category
    Analytical Chemistry
    Identifiers
    urn:nbn:se:uu:diva-80932 (URN)10.1039/b601660j (DOI)
    Available from: 2006-06-29 Created: 2006-06-29 Last updated: 2017-12-14Bibliographically approved
    8. Poly(dimethylsiloxane)-Based Microchip for Two-Dimensional Solid-Phase Extraction-Capillary Electrophoresis with an Integrated Electrospray Emitter Tip
    Open this publication in new window or tab >>Poly(dimethylsiloxane)-Based Microchip for Two-Dimensional Solid-Phase Extraction-Capillary Electrophoresis with an Integrated Electrospray Emitter Tip
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    2005 (English)In: Analytical Chemistry, ISSN 0003-2700, E-ISSN 1520-6882, Vol. 77, no 16, p. 5356-5363Article in journal (Refereed) Published
    Abstract [en]

    A microchip in poly(dimethylsiloxane) (PDMS) for in-line solid-phase extraction-capillary electrophoresis-electrospray ionization-time-of-flight mass spectrometry (SPE-CE-ESI-TOF-MS) has been developed and evaluated. The chip was fabricated in a novel one-step procedure where mixed PDMS was cast over steel wires in a mold. The removed wires defined 50-um cylindrical channels. Fused-silica capillaries were inserted into the structure in a tight fit connection. The inner walls of the inserted fused-silica capillaries and the PDMS microchip channels were modified with a positively charged polymer, PolyE-323. The chip was fabricated in a two-level cross design. The channel at the lower level was packed with 5-um hyper-cross-linked polystyrene beads acting as a SPE medium used for desalting. The upper level channel acted as a CE channel and ended in an integrated emitter tip coated with conducting graphite powder to facilitate the electrical contact for sheathless ESI. An overpressure continuously provided fresh CE electrolyte independently of the flows in the different levels. Further studies were carried out in order to investigate the electrophoretic and flow rate properties of the chip. Finally, six-peptide mixtures, in different concentrations, dissolved in physiological salt solution was injected, desalted, separated, and sprayed into the mass spectrometer for analysis with a limit of detection in femtomole levels.

    National Category
    Chemical Sciences
    Identifiers
    urn:nbn:se:uu:diva-74074 (URN)10.1021/ac050495g (DOI)16097780 (PubMedID)
    Available from: 2005-08-26 Created: 2005-08-26 Last updated: 2017-12-14Bibliographically approved
  • 11.
    Bergström, Sara K.
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry, Analytical Chemistry.
    Markides, Karin E.
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry, Analytical Chemistry.
    On-line coupling of microdialysis to packed capillary column liquid chromatography-tandem mass spectrometry demonstrated by measurement of free concentrations of ropivacaine and metabolite from spiked plasma samples2002In: Journal of chromatography. B, ISSN 1570-0232, E-ISSN 1873-376X, Vol. 775, no 1, p. 79-87Article in journal (Refereed)
    Abstract [en]

    An on-line coupling of microdialysis to a packed capillary column switching liquid chromatographic system (0.2 mm I.D.) and mass spectrometric detection was developed. The microdialysates were collected in the loop of the first of three valves, coupled in direct series. A deuterated internal standard was added on-line by the middle valve and the third valve operated both a pre-column, for desalting of the physiological buffer used in the sampling procedure, and a separation column. The on-line system was used to study free concentrations of ropivacaine and its metabolite (PPX) in human plasma samples. The analytes were detected by electrospray ionization in a tandem mass spectrometer operating in multiple reaction monitoring mode. The free fractions of ropivacaine (200 nM total concentration) and PPX (20 nM total concentration) in spiked plasma samples were 12±3 and 47±5% (±standard deviation for day-to-day variations, n=3), respectively.

  • 12.
    Bergström, Sara K
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry, Analytical Chemistry.
    Samskog, Jenny
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry, Analytical Chemistry.
    Markides, Karin E
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry, Analytical Chemistry.
    Development of a Poly(dimethylsiloxane) Interface for On-Line Capillary Column Liquid Chromatography: Capillary Electrophoresis Coupled to Sheathless Electrospray Ionization Time-of-Flight Mass Spectrometry2003In: Analytical Chemistry, ISSN 0003-2700, E-ISSN 1520-6882, Vol. 75, no 20, p. 5461-5467Article in journal (Refereed)
    Abstract [en]

    An interface in elastomeric poly(dimethylsiloxane) (PDMS) for on-line orthogonal coupling of packed capillary liquid chromatography (LC) (i.d. = 0.2 mm) with capillary electrophoresis (CE) in combination with sheathless electrospray ionization (ESI) time-of-flight mass spectrometric (TOFMS) detection is presented. The new interface has a two-level design, which in combination with a continuous CE electrolyte flow through the interface provides integrity of the LC effluent and the CE separation until an injection is desired. The transparent and flexible PDMS material was found to have a number of advantages when combined with fused silica column technology, including ease to follow the process and ease to exchange columns. By combining conventional microscale systems of LC, CE, and ESI−MS, respectively, the time scales of the individual dimensions were harmonized for optimal peak capacity per unit time. The performance of the LC−CE−TOFMS system was evaluated using peptides as model substances. A S/N of about 330 was achieved for leucine-enkephaline from a 0.5 μL LC injection of 25 μg/mL peptide standard.

  • 13.
    Bergström, S.K.
    et al.
    Uppsala University, Teknisk-naturvetenskapliga vetenskapsområdet, Chemistry, Department of Chemistry.
    Samskog, J.
    Markides, K.E.
    Development of a Poly(dimethylsiloxane) Interface for On-Line Capillary Column Liquid Chromatography-Capillary Electrophoresis Coupled to Sheathless Electrospray Ionization Time-of-Flight Mass Spectrometry2003In: Anal. Chem., no 75, p. 5461-5467Article in journal (Refereed)
  • 14.
    Bylund, D.
    et al.
    Uppsala University, Teknisk-naturvetenskapliga vetenskapsområdet, Chemistry, Department of Chemistry.
    Danielsson, R.
    Malmquist, G.
    Markides, K.E.
    Chromatographic alignment by warping and dynamic programming as a pre-processing tool for PARAFAC modelling of liquid chromatography - mass spectrometry data2002In: J. of Chromatography A, no 961, p. 237-244Article in journal (Refereed)
  • 15.
    Bylund, D.
    et al.
    Uppsala University, Teknisk-naturvetenskapliga vetenskapsområdet, Chemistry, Department of Chemistry.
    Samskog, J.
    Jacobsson, S.P.
    Markides, K.E.
    Classification of Lactate Dehydrogenase of Different Origin by Liquid Chromatography-Mass Spectrometry and Multivariate Analysis2003In: J. Am. Soc. Mass Spectrom., no 14, p. 236-240Article in journal (Refereed)
  • 16.
    Bökman, C. Fredrik
    Uppsala University, Teknisk-naturvetenskapliga vetenskapsområdet, Chemistry, Department of Chemistry, Analytical Chemistry.
    Analytical Aspects of Atmospheric Pressure Ionisation in Mass Spectrometry2002Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    The actual signal recorded with an analytical instrument is not always a true reflection of the analysed sample. In this thesis a further insight of the atmospheric pressure ionisation processes electrospray (ESI) and atmospheric pressure chemical ionisation (APCI) has been endeavoured, to provide a deeper understanding of and ways to minimize this bias.

    A response model for ESI has been modified and used to study the influence of solvent composition on the observed mass spectrometric signal. The response model divides the response into an analyte partitioning coefficient and an instrumental response factor. A number of experimental parameters influencing the response were investigated including spray position relative to the orifice, spray potential, nebulizer and curtain gas flow rates, ionic strength and organic content of the sprayed solution. The history of the generated droplets turned out to be of significant importance to both the partitioning coefficients and the instrumental response factor. Furthermore, it was found that the total ionic strength and not only the electrolyte concentration will influence the instrumental response factor.

    In addition, based on the importance of hydrophobicity and electrophoretic mobility, a model was proposed for the ion distribution within the electrosprayed droplets.

    The coupling of an electrochemical (EC) cell to a mass spectrometric (MS) system has been evaluated. The coupling of the EC cell to the MS was made to decouple the cell from the high voltage circuit of the ESI. The feasibility for analyte ionisation, sample pre-concentration and solvent exchange as well as studying redox reaction products was shown.

  • 17.
    Dahlin, Andreas
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry.
    Microscale Tools for Sample Preparation, Separation and Detection of Neuropeptides2005Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    The analysis of low abundant biological molecules is often challenging due to their chemical properties, low concentration and limited sample volumes. Neuropeptides are one group of molecules that fits these criteria. Neuropeptides also play an important role in biological functions, which makes them extra interesting to analyze. A classic chemical analysis involves sampling, sample preparation, separation and detection. In this thesis, an enhanced solid supported microdialysis method was developed and used as a combined sampling- and preparation technique. In general, significantly increased extraction efficiency was obtained for all studied peptides. To be able to control the small sample volumes and to minimize the loss of neuropeptides because of unwanted adsorption onto surfaces, the subsequent analysis steps were miniaturized to a micro total analysis system (µ-TAS), which allowed sample pre-treatment, injection, separation, manipulation and detection.

    In order to incorporate these analysis functions to a microchip, a novel microfabrication protocol was developed. This method facilitated three-dimensional structures to be fabricated without the need of clean room facilities.

    The sample pre-treatment step was carried out by solid phase extraction from beads packed in the microchip. Femtomole levels of neuropeptides were detected from samples possessing the same properties as microdialysates. The developed injection system made it possible to conduct injections from a liquid chromatographic separation into a capillary electrophoresis channel, which facilitated for advanced multidimensional separations. An electrochemical sample manipulation system was also developed. In the last part, different electrospray emitter tip designs made directly from the edge of the microchip substrate were developed and evaluated. The emitters were proven to be comparable with conventional, capillary based emitters in stability, durability and dynamic flow range. Although additional developments remain, the analysis steps described in this thesis open a door to an integrated, on-line µ-TAS for neuropeptides analysis in complex biological samples.

    List of papers
    1. A feasibility study of solid supported enhanced microdialysis
    Open this publication in new window or tab >>A feasibility study of solid supported enhanced microdialysis
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    2004 (English)In: Analytical Chemistry, ISSN 0003-2700, E-ISSN 1520-6882, Vol. 76, no 6, p. 1678-1682Article in journal (Refereed) Published
    Abstract [en]

    For the first time, a solid supported enhanced microdialysis methodology for analysis of neuropeptides is described. The microdialysis samples were, in this study, subsequently collected in fractions, dissolved from the solid particles, dried, and resolved in a formic acid buffer in order to make them suitable for capillary liquid chromatography-mass spectrometry. Different microdialysis flow profiles were evaluated where air-gapped continuous flow was considered most suitable for the solid supported microdialysis mode. Six endogenous neuropeptides were initially used to investigate the feasibility of this enhanced microdialysis methodology. The improved relative recovery obtained from the solid supported enhanced microdialysis was varying from no effect to 10 times higher as compared to ordinary microdialysis. The most efficient enrichment was obtained for luteinizing hormone releasing hormone, which was the largest but also the most hydrophilic of the peptides. In contrast, no significant difference in recovery was observed for Leu-enkephalin being the smallest and the most hydrophobic peptide tested. These results indicate an increased flux and selective uptake of hydrophilic peptides across the membrane and enrichment on the particles in solid supported microdialysis.

    National Category
    Natural Sciences
    Identifiers
    urn:nbn:se:uu:diva-93181 (URN)10.1021/ac035305l (DOI)15018567 (PubMedID)
    Available from: 2005-05-10 Created: 2005-05-10 Last updated: 2017-12-14Bibliographically approved
    2. Poly(dimethylsiloxane)-Based Microchip for Two-Dimensional Solid-Phase Extraction-Capillary Electrophoresis with an Integrated Electrospray Emitter Tip
    Open this publication in new window or tab >>Poly(dimethylsiloxane)-Based Microchip for Two-Dimensional Solid-Phase Extraction-Capillary Electrophoresis with an Integrated Electrospray Emitter Tip
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    2005 (English)In: Analytical Chemistry, ISSN 0003-2700, E-ISSN 1520-6882, Vol. 77, no 16, p. 5356-5363Article in journal (Refereed) Published
    Abstract [en]

    A microchip in poly(dimethylsiloxane) (PDMS) for in-line solid-phase extraction-capillary electrophoresis-electrospray ionization-time-of-flight mass spectrometry (SPE-CE-ESI-TOF-MS) has been developed and evaluated. The chip was fabricated in a novel one-step procedure where mixed PDMS was cast over steel wires in a mold. The removed wires defined 50-um cylindrical channels. Fused-silica capillaries were inserted into the structure in a tight fit connection. The inner walls of the inserted fused-silica capillaries and the PDMS microchip channels were modified with a positively charged polymer, PolyE-323. The chip was fabricated in a two-level cross design. The channel at the lower level was packed with 5-um hyper-cross-linked polystyrene beads acting as a SPE medium used for desalting. The upper level channel acted as a CE channel and ended in an integrated emitter tip coated with conducting graphite powder to facilitate the electrical contact for sheathless ESI. An overpressure continuously provided fresh CE electrolyte independently of the flows in the different levels. Further studies were carried out in order to investigate the electrophoretic and flow rate properties of the chip. Finally, six-peptide mixtures, in different concentrations, dissolved in physiological salt solution was injected, desalted, separated, and sprayed into the mass spectrometer for analysis with a limit of detection in femtomole levels.

    National Category
    Chemical Sciences
    Identifiers
    urn:nbn:se:uu:diva-74074 (URN)10.1021/ac050495g (DOI)16097780 (PubMedID)
    Available from: 2005-08-26 Created: 2005-08-26 Last updated: 2017-12-14Bibliographically approved
    3. A simplified multidimensional approach for analysis of complex biological samples: on-line LC-CE-MS
    Open this publication in new window or tab >>A simplified multidimensional approach for analysis of complex biological samples: on-line LC-CE-MS
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    2006 (English)In: The Analyst, ISSN 0003-2654, E-ISSN 1364-5528, Vol. 131, no 7, p. 791-798Article in journal (Refereed) Published
    Abstract [en]

    Information on protein expression, disease biomarkers or surrogate markers and genetic disorders can nowadays be achieved from analysis of complex biological samples by liquid separation coupled to mass spectrometric (MS) detection. This paper describes fast multidimensional separation by on-line liquid chromatography (LC) and capillary electrophoresis (CE), followed by electrospray ionization (ESI) Fourier transform ion cyclotron resonance (FTICR) MS detection. This detector provides ultrahigh resolution of the detected ions, mass accuracy at the ppm-level and high sensitivity. Most of the challenge of this system lies in the development of a new interface for the on-line coupling of LC to CE. The interface developed in poly(dimethylsiloxane) provides a RSD for injection repeatability of <3.5% and surface control for unspecific binding by deactivation with a cationic polymer, PolyE-323. We have evaluated the interface, as well as the overall system, with respect to robustness and deconvolution ability. Sequence coverage for bovine serum albumin (BSA) of 93% showed a high recovery of sample in the different transfer steps through the system. The detection limit for identification is 277 ng mL−1 (or 280 nM) on average for peptides. In the future, we expect LC-CE-MS to be a novel strategy for elucidating the chemistry of biological matrices.

    National Category
    Analytical Chemistry
    Identifiers
    urn:nbn:se:uu:diva-80932 (URN)10.1039/b601660j (DOI)
    Available from: 2006-06-29 Created: 2006-06-29 Last updated: 2017-12-14Bibliographically approved
    4. On-line coupling of a microelectrode array equipped poly(dimethylsiloxane) microchip with an integrated graphite electrospray tip to electrospray mass spectrometry
    Open this publication in new window or tab >>On-line coupling of a microelectrode array equipped poly(dimethylsiloxane) microchip with an integrated graphite electrospray tip to electrospray mass spectrometry
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    In: Article in journal (Refereed) Submitted
    Identifiers
    urn:nbn:se:uu:diva-93184 (URN)
    Available from: 2005-05-10 Created: 2005-05-10 Last updated: 2011-03-21
    5. Sheathless electrospray from polymer microchips
    Open this publication in new window or tab >>Sheathless electrospray from polymer microchips
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    2003 In: Analytical Chemistry, Vol. 75, no 15, p. 3934-3940Article in journal (Refereed) Published
    Identifiers
    urn:nbn:se:uu:diva-93185 (URN)
    Available from: 2005-05-10 Created: 2005-05-10 Last updated: 2011-03-21
    6. Capillary electrophoresis coupled to mass spectrometry from a polymer modified poly(dimethylsiloxane) microchip with an integrated graphite electrospray tip
    Open this publication in new window or tab >>Capillary electrophoresis coupled to mass spectrometry from a polymer modified poly(dimethylsiloxane) microchip with an integrated graphite electrospray tip
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    2005 (English)In: The Analyst, ISSN 0003-2654, E-ISSN 1364-5528, Vol. 130, no 2, p. 193-199Article in journal (Refereed) Published
    Abstract [en]

    Hybrid capillary-poly(dimethysiloxane) (PDMS) microchips with integrated electrospray ionization (ESI) tips were directly fabricated by casting PDMS in a mould. The shapes of the emitter tips were drilled into the mould, which produced highly reproducible three-dimensional tips. Due to the fabrication method of the microfluidic devices, no sealing was necessary and it was possible to produce a perfect channel modified by PolyE-323, an aliphatic polyamine coating agent. A variety of different coating procedures were also evaluated for the outside of the emitter tip. Dusting graphite on a thin unpolymerised PDMS layer followed by polymerisation was proven to be the most suitable procedure. The emitter tips showed excellent electrochemical properties and durabilities. The coating of the emitter was eventually passivated, but not lost, and could be regenerated by electrochemical means. The excellent electrochemical stability was further confirmed in long term electrospray experiments, in which the emitter sprayed continuously for more than 180 h. The PolyE-323 was found suitable for systems that integrate rigid fused silica and soft PDMS technology, since it simply could be applied successfully to both materials. The spray stability was confirmed from the recording of a total ion chromatogram in which the electrospray current exhibited a relative standard deviation of 3.9% for a 30 min run. CE-ESI-MS separations of peptides were carried out within 2 min using the hybrid PDMS chip resulting in similar efficiencies as for fused silica capillaries of the same length and thus with no measurable band broadening effects, originating from the PDMS emitter.

    National Category
    Analytical Chemistry Inorganic Chemistry
    Identifiers
    urn:nbn:se:uu:diva-93084 (URN)10.1039/b414592e (DOI)15665973 (PubMedID)
    Available from: 2005-05-03 Created: 2005-05-03 Last updated: 2017-12-14Bibliographically approved
    7. Sample pretreatment on a microchip with an integrated electrospray emitter
    Open this publication in new window or tab >>Sample pretreatment on a microchip with an integrated electrospray emitter
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    2006 (English)In: Electrophoresis, ISSN 0173-0835, E-ISSN 1522-2683, Vol. 27, no 11, p. 2075-2082Article in journal (Refereed) Published
    Keyword
    Electrospray emitter, Microchip, PDMS, Sample pretreatment
    National Category
    Chemical Sciences Engineering and Technology
    Identifiers
    urn:nbn:se:uu:diva-95129 (URN)10.1002/elps.200500763 (DOI)
    Available from: 2006-11-17 Created: 2006-11-17 Last updated: 2017-12-14Bibliographically approved
  • 18.
    Danielsson, R.
    et al.
    Uppsala University, Teknisk-naturvetenskapliga vetenskapsområdet, Chemistry, Department of Chemistry.
    Bylund, D.
    Markides, K.E.
    Matched filtering with background suppression for improved quality of base peak chromatograms and mass spectra in liquid chromatography - mass spectrometry2002In: Analytica Chimica Acta, no 454, p. 167-184Article in journal (Refereed)
  • 19.
    Ericsson, D.
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry.
    Bergquist, J.
    Ultrasensitive MALDI-TOF MS with picoliter volume sample handling2002In: Mass spectrometry and Hyphenated Techniques in Neuropeptide Research, John Wiley & Sons, N.Y. , 2002, Vol. Chapter 9, p. 235-255Chapter in book (Refereed)
  • 20.
    Ericsson, D.
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry.
    Ekström, S.Nilsson, J.Bergquist, JonasUppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry, Analytical Chemistry.Marko-Varga, G.Laurell, T.
    Dispenser-aided nanodigestion for rapid protein identification in MALDI-TOF nanovial arrays2001Conference proceedings (editor) (Other academic)
  • 21.
    Fernandez, F.
    et al.
    Uppsala University, Teknisk-naturvetenskapliga vetenskapsområdet, Chemistry, Department of Chemistry.
    Vadillo, J.
    Kimmel, J.
    Wetterhall, M.
    Hadamar transform time-of-flight mass spectrometry: A high-speed detector for capillary-format separations2002In: Anal. Chem., no 74, p. 1611-1617Article in journal (Refereed)
  • 22.
    Frank, A.
    et al.
    Uppsala University, Teknisk-naturvetenskapliga vetenskapsområdet, Chemistry, Department of Chemistry.
    Wibom, R.
    Danielsson, R.
    Myocardial cytomchrom c oxidase activity in Swedish moose (Alces alces L.) affected by molybdenosis2002In: Science of theTotal Environment, no 290, p. 121-129Article in journal (Refereed)
  • 23.
    Färnert Lindber, A.
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry.
    Gil, J
    Sweberg, A
    Bergqvist, G
    Thapar, Y
    Lindegårdh, M M
    Berezcky, N
    Björkman, S
    Evidence of Plasmodium falciparum malaria resistant to atovaquone and proguanil hydrochloride: case reports2003In: BMJ, no 326, p. 628-629Article in journal (Refereed)
  • 24. Hong, M
    et al.
    Sudor, J
    Stefansson, M
    Uppsala University, Teknisk-naturvetenskapliga vetenskapsområdet, Chemistry, Department of Chemistry.
    Novotny, M V
    High-resolution studies on hyaluronic acid mixtures through capillary gel electrophoresis1998In: Analytical Chemistry, ISSN 1520-6882, Vol. 70, p. 568-573Article in journal (Refereed)
  • 25.
    Isaac, G.
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry.
    Bylund, D.
    Månsson, J-E.
    Markides, K.E.
    Bergquist, J.
    Analysis of phosphatidylcholine and sphingomyelin molecular species from brain extracts using capillary liquid chromatography electrospray ionization mass spectrometry2003In: J. of Neuroscience Methods, no 128, p. 111-119Article in journal (Refereed)
  • 26.
    Isaac, Giorgis
    Uppsala University, Teknisk-naturvetenskapliga vetenskapsområdet, Chemistry, Department of Chemistry, Analytical Chemistry.
    Development of Enhanced Analytical Methodology for Lipid Analysis from Sampling to Detection: A Targeted Lipidomics Approach2005Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    This thesis covers a wide range of analytical method development for lipid analysis in complex biological samples; from sample preparation using pressurized fluid extraction (PFE) and separation with reversed phase capillary liquid chromatography (RP-LC) to detection by electrospray ionization mass spectrometry (ESI/MS) and tandem MS.

    The requirements for fast, reliable and selective extraction methods with minimal usage of solvents have accelerated the development of new extraction techniques. PFE is one of the new automated, fast and efficient liquid extraction techniques which use elevated temperature and pressure with standard liquid solvents. In this thesis the reliability and efficiency of the PFE technique was investigated for the extraction of total lipid content from cod, herring muscle and human brain tissue as well as for pesticides from fatty foodstuffs. Improved or comparable efficiencies were achieved with reduced time and solvent consumption as compared to traditional methods.

    A RP-LC coupled online to ESI/MS for the analysis of phosphatidylcholine (PC) and sphingomyelin (SM) molecular species was developed and used for the analysis of brain lipids from eight groups of mice treated with vehicle and various neuroleptics. The effect of postnatal iron administration in lipid composition and behavior was investigated. Whether or not these effects could be altered by subchronic administration of the neuroleptics (clozapine and haloperidol) were examined. The results support the hypothesis that an association between psychiatric disorders, behavior abnormalities and lipid membrane constitution in the brain exists.

    Finally, a tandem MS precursor ion scan was used to analyze the developmental profile of brain sulfatide accumulation in arylsulfatase A (ASA) deficient (ASA -/-) as compared to wild type control (ASA +/+) mice. The ASA -/- mice were developed as a model of the monogenic disease metachromatic leukodystrophy with an established deficiency of the lysosomal enzyme ASA. The results showed that an alteration in the composition of sulfatide molecular species was observed between the ASA -/- and ASA +/+ mice.

    This thesis shows that modern analytical methods can provide new insights in the extraction and analysis of lipids from complex biological samples.

    List of papers
    1. Total Lipid Extraction of Homogenized and Intact Lean Fish Muscles Using Pressurized Fluid Extraction and Batch Extraction Technique
    Open this publication in new window or tab >>Total Lipid Extraction of Homogenized and Intact Lean Fish Muscles Using Pressurized Fluid Extraction and Batch Extraction Technique
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    2005 (English)In: Journal of Agricultural and Food Chemistry, ISSN 0021-8561, E-ISSN 1520-5118, Vol. 53, no 14, p. 5506-5512Article in journal (Refereed) Published
    Abstract [en]

    The reliability and efficiency of pressurized fluid extraction (PFE) technique for the extraction of total lipid content from cod and the effect of sample treatment on the extraction efficiency have been evaluated. The results were compared with two liquid-liquid extraction methods, traditional and modified methods according to Jensen. Optimum conditions were found to be with 2-propanol/n-hexane (65:35, v/v) as a first and n-hexane/diethyl ether (90:10, v/v) as a second solvent, 115 oC, and 10 min of static time. PFE extracts were cleaned up using the same procedure as in the methods according to Jensen. When total lipid yields obtained from homogenized cod muscle using PFE were compared yields obtained with original and modified Jensen methods, PFE gave significantly higher yields, ~10% higher (t test, P < 0.05). Infrared and NMR spectroscopy suggested that the additional material that inflates the gravimetric results is rather homogeneus and is primarily consists of phospholipid with headgroups of inositidic and/or glycosidic nature. The comparative study demonstrated that PFE is an alternative suitable technique to extract total lipid content from homogenized cod (lean fish) and herring (fat fish) muscle showing a precision comparable to that obtained with the traditional and modified Jensen methods. Despite the necessary cleanup step, PFE showed important advantages in the solvent consumption was cut by ~50% and automated extraction was possible.

    Keyword
    Lean fish, phospholipids, pressurized fluid extraction, PFE, total lipid content
    National Category
    Natural Sciences
    Identifiers
    urn:nbn:se:uu:diva-93095 (URN)10.1021/jf0501286 (DOI)15998106 (PubMedID)
    Available from: 2005-04-29 Created: 2005-04-29 Last updated: 2017-12-14Bibliographically approved
    2. Pressurized Fluid Extraction (PFE) as an Alternative General Method for the Determination of Pesticide Residues in Rape Seed
    Open this publication in new window or tab >>Pressurized Fluid Extraction (PFE) as an Alternative General Method for the Determination of Pesticide Residues in Rape Seed
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    2002 In: The Analyst, ISSN 0003-2654, Vol. 127, no 4, p. 554-559Article in journal (Refereed) Published
    Identifiers
    urn:nbn:se:uu:diva-93096 (URN)
    Available from: 2005-04-29 Created: 2005-04-29Bibliographically approved
    3. Analysis of Phosphatidylcholine and Sphingomyelin Molecular Species From Brain Extracts Using Capillary Liquid Chromatography Electrospray Ionization Mass Spectrometry
    Open this publication in new window or tab >>Analysis of Phosphatidylcholine and Sphingomyelin Molecular Species From Brain Extracts Using Capillary Liquid Chromatography Electrospray Ionization Mass Spectrometry
    Show others...
    2003 In: Journal of Neuroscience Methods, ISSN 0165-0270, Vol. 128, no 1-2, p. 111-119Article in journal (Refereed) Published
    Identifiers
    urn:nbn:se:uu:diva-93097 (URN)
    Available from: 2005-04-29 Created: 2005-04-29 Last updated: 2011-03-21
    4. Brain Lipid Composition in Postnatal Iron-Induced Motor Behavior Alterations Following Chronic Neuroleptic Administration in Mice
    Open this publication in new window or tab >>Brain Lipid Composition in Postnatal Iron-Induced Motor Behavior Alterations Following Chronic Neuroleptic Administration in Mice
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    In: Neuroscience LettersArticle in journal (Refereed) Submitted
    Identifiers
    urn:nbn:se:uu:diva-93098 (URN)
    Available from: 2005-04-29 Created: 2005-04-29 Last updated: 2011-03-21
    5. Characterization of Brain Sulfatide Molecular Species in Arylsulfatase A Deficient Mice Using Electrospray Ionization Tandem Mass Spectrometry
    Open this publication in new window or tab >>Characterization of Brain Sulfatide Molecular Species in Arylsulfatase A Deficient Mice Using Electrospray Ionization Tandem Mass Spectrometry
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    Manuscript (Other academic)
    Identifiers
    urn:nbn:se:uu:diva-93099 (URN)
    Available from: 2005-04-29 Created: 2005-04-29 Last updated: 2011-03-21
  • 27. Jastrebova, J
    et al.
    Nyholm, L
    Uppsala University, Teknisk-naturvetenskapliga vetenskapsområdet, Chemistry, Department of Chemistry.
    Markides, K
    Uppsala University, Teknisk-naturvetenskapliga vetenskapsområdet, Chemistry, Department of Chemistry.
    Bergqvist, Y
    Uppsala University, Teknisk-naturvetenskapliga vetenskapsområdet, Chemistry, Department of Chemistry.
    On-Line Deoxygenation for Reductive Electrochemical Detection of Artemisinin and Dihydroartemisinin in Liquid Chromatography1998In: The Analyst, ISSN 0003-2654, Vol. 123, p. 313-Article in journal (Refereed)
  • 28.
    Klett, O.
    et al.
    Uppsala University, Teknisk-naturvetenskapliga vetenskapsområdet, Chemistry, Department of Chemistry.
    Nischang, I.
    Nyholm, L.
    Deviceless decoupled electrochemical detection of catecholamines in capillary electrophoresis using gold microband array electrodes2002In: Electrophoresis, no 23, p. 3678-3682Article in journal (Refereed)
  • 29.
    Klett, Oliver
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry.
    Electrochemical Aspects of Miniaturized Analytical Platforms2003Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    This thesis ties some electrochemical aspects of development and fabrication of an analytical system on a microchip together. These aspects develop through the fundamentals of amperometric detection in microsystems and microfabrication via the interaction of electrochemical detection and electrophoretic separation finally to the interfacing of a microsystem to the macro world.

    Paper I deals with amperometric detection in microscale systems and describes the fabrication of the necessary on-chip microelectrodes together with fluidic channels in silicon. It was furthermore studied, if the interelectrode distance of some μm could be used to improve the sensitivity in amperometric detection by employing redox cycling.

    Papers II, III and IV deal with the effect of a high voltage field on amperometric detection. In analytical microdevices typically an electrophoretic separation step (e.g. capillary electrophoresis, CE) precedes the detection. The interference of the CE high voltage with the amperometric detection potential is often considered one of the main hindrances for an effective combination of these techniques. In paper II one reason for the observed disturbing potential shift was elucidated. It was shown that positioning of working electrode and reference electrode on an equipotiental surface eliminates this problem. Paper III reports an application of this technique. In paper IV it could be shown that this approach could further be used to significantly reduce the instrumental requirements for amperometric detection in CE.

    Papers V, VI, VII, finally discuss the interfacing of low volumetric flows that typically occur on microanalytical devices to other techniques. Both, interfacing from liquid to liquid phase (μLC to CE in paper V) and from liquid to gas phase (CE to MS in paper VI and VII) were discussed. Electrochemical methods are used in this context to evaluate the stability and, in paper VI and VII, to increase the understanding of underlying processes of corrosion.

    List of papers
    1. Design of a Chip Based Microanalytical Fluidic System Based on Electrochemical Detection Using Redox Cycling
    Open this publication in new window or tab >>Design of a Chip Based Microanalytical Fluidic System Based on Electrochemical Detection Using Redox Cycling
    Show others...
    1999 In: MEMS-Proceedings of the ASME International Mechanical Engineering, Congress and Exposition, Vol. 1, no 1, p. 511-516Article in journal (Refereed) Published
    Identifiers
    urn:nbn:se:uu:diva-90119 (URN)
    Available from: 2003-03-07 Created: 2003-03-07 Last updated: 2012-06-20
    2. Elimination of High Voltage Field Effects in End Column Electrochemical Detection in Capillary Electrophoresis by use of On-Chip Microband Electrodes
    Open this publication in new window or tab >>Elimination of High Voltage Field Effects in End Column Electrochemical Detection in Capillary Electrophoresis by use of On-Chip Microband Electrodes
    2001 In: Analytical Chemistry, Vol. 73, no 8, p. 1909-1915Article in journal (Refereed) Published
    Identifiers
    urn:nbn:se:uu:diva-90120 (URN)
    Available from: 2003-03-07 Created: 2003-03-07Bibliographically approved
    3. III. Deviceless Decoupled Electrochemical Detection of Catecholamines in Capillary Electrophoresis using Gold Microband Array Electrodes
    Open this publication in new window or tab >>III. Deviceless Decoupled Electrochemical Detection of Catecholamines in Capillary Electrophoresis using Gold Microband Array Electrodes
    2002 In: Electrophoresis, Vol. 23, p. 3678-3682Article in journal (Refereed) Published
    Identifiers
    urn:nbn:se:uu:diva-90121 (URN)
    Available from: 2003-03-07 Created: 2003-03-07Bibliographically approved
    4. Separation High Voltage-Field Driven On-Chip Amperometric Detection in Capillary Electrophoresis
    Open this publication in new window or tab >>Separation High Voltage-Field Driven On-Chip Amperometric Detection in Capillary Electrophoresis
    2003 In: Analytical Chemistry, Vol. 74, no 6, p. 1245-1250Article in journal (Refereed) Published
    Identifiers
    urn:nbn:se:uu:diva-90122 (URN)
    Available from: 2003-03-07 Created: 2003-03-07Bibliographically approved
    5. On-column polymer-imbedded graphite inlet electrode for capillary electrophoresis coupled on-line with flow injection analysis in a poly(dimethylsiloxane) interface
    Open this publication in new window or tab >>On-column polymer-imbedded graphite inlet electrode for capillary electrophoresis coupled on-line with flow injection analysis in a poly(dimethylsiloxane) interface
    Show others...
    2003 (English)In: Electrophoresis, ISSN 0173-0835, E-ISSN 1522-2683, Vol. 24, no 11, p. 1723-1729Article in journal (Refereed) Published
    Abstract [en]

    A method for coupling an electrophoretic driven separation to a liquid flow, using conventional fused-silica capillaries and a soft polymeric interface is presented. A novel design of the electrode providing high voltage to the electrophoretic separation was also developed. The electrode consisted of a conductive polyimide/graphite imbedded coating immobilized onto the capillary electrophoresis (CE) column inlet. This integrated electrode gave the same separation performance as a commonly used platinum electrode. The on-column electrode also showed good electrochemical stability in chronoamperometric experiments. In addition, with this electrode design, the electrode position relative to the inlet end of the CE column will always be constant and well defined. The on-line flow injection analysis (FIA)-CE system was used with electrospray ionization (ESI)-time of flight (TOF)-mass spectrometry detection. The preparation of the PDMS (poly(dimethylsiloxane)) interface for FIA-CE is described in detail and used for initial tests of the on-column polymer-imbedded graphite inlet electrode. In this interface, a pressure-driven liquid flow, a make up CE electrolyte and a CE column inlet meet in a two-level cross (95 μm ID) in the PDMS structure, enabling independent flow characterization.

    Keyword
    Capillary electrophoresis, Flow injection, Hyphenation, On-column electrode, Poly(dimethylsiloxane)
    National Category
    Chemical Sciences
    Identifiers
    urn:nbn:se:uu:diva-94267 (URN)10.1002/elps.200305362 (DOI)
    Available from: 2006-04-07 Created: 2006-04-07 Last updated: 2017-12-14Bibliographically approved
    6. Titanium/Gold Coated Fused Silica Sheathless Electrospray Emitters
    Open this publication in new window or tab >>Titanium/Gold Coated Fused Silica Sheathless Electrospray Emitters
    2003 In: Rapid communications in Mass Spectrometry, Vol. 17, no 14, p. 1535-1540Article in journal (Refereed) Published
    Identifiers
    urn:nbn:se:uu:diva-90124 (URN)
    Available from: 2003-03-07 Created: 2003-03-07Bibliographically approved
    7. A Comparison of the Electrochemical Stabilities of some Metal, Polymer and Carbon Coated Nanospray Emitters
    Open this publication in new window or tab >>A Comparison of the Electrochemical Stabilities of some Metal, Polymer and Carbon Coated Nanospray Emitters
    2003 In: Analyst, Vol. 128, no 6, p. 728-733Article in journal (Refereed) Published
    Identifiers
    urn:nbn:se:uu:diva-90125 (URN)
    Available from: 2003-03-07 Created: 2003-03-07 Last updated: 2011-03-21
  • 30.
    Koivisto, Pernilla
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry, Analytical Chemistry.
    Bergström, Sara K.
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry, Analytical Chemistry.
    Markides, Karin E.
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry, Analytical Chemistry.
    Determination of the free concentration of ropivacaine in plasma by packed capillary liquid chromatography: A comparison of ultrafiltration and microdialysis as sample preparation methods2001In: Journal of Microcolumn Separations, ISSN 1040-7685, E-ISSN 1520-667X, Vol. 13, no 5, p. 197-201Article in journal (Refereed)
    Abstract [en]

    In this study, ultrafiltration and microdialysis have been compared as sample preparation methods to separate the free fraction of ropivacaine from the protein bound in 150 μL plasma. A liquid chromatographic system with packed capillary columns (0.2 mm internal diameter) was used to enhance sensitivity when analyzing the small sample volumes obtained after the ultrafiltration and the microdialysis. The microdialysis was performed with probes of our own construction, and to save analysis time, the microdialysis sampling was coupled on-line to the liquid chromatographic system. The reduction of back pressure in the microdialysis outlet tube and in the injector was found to be essential. The free fraction obtained with each method was equivalent: both gave a free fraction of 6%.

  • 31.
    Lavén, Martin
    Uppsala University, Teknisk-naturvetenskapliga vetenskapsområdet, Chemistry, Department of Chemistry.
    Liquid Chromatography – Mass Spectrometry Analysis of Short-lived Tracers in Biological Matrices: Exploration of Radiotracer Chemistry as an Analytical Tool2005Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    Liquid chromatography – mass spectrometry (LC-MS) methods were developed for the analysis of positron emission tomography (PET) radiotracers in biological matrices. Additionally, radiotracer chemistry was explored as an analytical tool for supporting LC-MS method development and imaging molecular interactions in miniaturised chemical analysis systems.

    Conventional radiodetection methods can offer high sensitivity in the analysis of radiotracers in biological matrices, although with the short half-life of PET tracers, this mass sensitivity decreases rapidly with time. This limits the time frame for analysis, and may compromise the precision and accuracy of the later measurements. Performing LC-MS analysis of the dominant stable isotope form of the tracer removes such time restrictions.

    An LC-MS/MS method was developed for determination of the tracer flumazenil in human plasma, with high inter-assay precision (RSD < 7%) and accuracy (95 – 104%). The method was applied in a multiple scan PET study where the plasma concentration spanned from 0.07 to 0.21 nM. The method removed the time restrictions associated with radiodetection methods and thus provided the opportunity of analysing a greater number of samples than would have been possible with radioanalysis.

    Furthermore, an LC-MS/MS method was developed that provided an efficient metabolic screening tool of potential PET tracers, whereby the substrates could be collected directly from 11C-labelling batches. This permitted repeated incubation experiments without the need of repeated labelling syntheses. A para-methoxy-benzamide analogue of the radiotracer WAY-100635 was thus identified as a potential tracer with improved metabolic stability. Additionally, a capillary LC-MS method was developed with rapid (0.75 min) and efficient (> 99%) on-line high flow-rate extraction for determination of metabolic stability of PET radiotracers.

    Finally, the concept of radionuclide imaging of miniaturised chemical analysis systems was demonstrated with the direct study of interactions within capillary extraction columns and microchannels moulded in a plastic CD and poly(dimethylsiloxane).

    List of papers
    1. Determination of flumazenil in human plasma by liquid chromatography - electrospray ionisation - tandem mass spectrometry
    Open this publication in new window or tab >>Determination of flumazenil in human plasma by liquid chromatography - electrospray ionisation - tandem mass spectrometry
    Show others...
    2004 In: Journal of Chromatography B, Vol. 808, p. 221-227Article in journal (Refereed) Published
    Identifiers
    urn:nbn:se:uu:diva-92490 (URN)
    Available from: 2005-01-11 Created: 2005-01-11Bibliographically approved
    2. Analysis of microsomal metabolic stability using high-flow-rate extraction coupled to capillary liquid chromatography–mass spectrometry
    Open this publication in new window or tab >>Analysis of microsomal metabolic stability using high-flow-rate extraction coupled to capillary liquid chromatography–mass spectrometry
    2004 In: Journal of Chromatography B, Vol. 806, p. 119-126Article in journal (Refereed) Published
    Identifiers
    urn:nbn:se:uu:diva-92491 (URN)
    Available from: 2005-01-11 Created: 2005-01-11Bibliographically approved
    3. Determination of metabolic stability of positron emission tomography tracers by LC-ESI-MS/MS: an example in WAY-100635 and two analogues
    Open this publication in new window or tab >>Determination of metabolic stability of positron emission tomography tracers by LC-ESI-MS/MS: an example in WAY-100635 and two analogues
    In: Journal of Pharmaceutical and Biomedical AnalysisArticle in journal (Refereed) Submitted
    Identifiers
    urn:nbn:se:uu:diva-92492 (URN)
    Available from: 2005-01-11 Created: 2005-01-11Bibliographically approved
    4. Radionuclide Imaging of Miniaturized Chemical Analysis Systems
    Open this publication in new window or tab >>Radionuclide Imaging of Miniaturized Chemical Analysis Systems
    Show others...
    2004 (English)In: Analytical Chemistry, ISSN 0003-2700, E-ISSN 1520-6882, Vol. 76, no 23, p. 7102-7108Article in journal (Refereed) Published
    Abstract [en]

    We propose radionuclide imaging as a valuable tool for the study of molecular interactions in miniaturized systems for chemical analysis. Sensitive and quantitative imaging can be performed with compounds labeled with short-lived positron-emitting radionuclides, such as C-11 and Ga-68, within selected parts of the system. Radionuclide imaging is not restricted to transparent materials since the relatively energetic positrons can penetrate high optical density materials. Experimentally, a radiotracer is introduced into the object of study, which is subsequently placed on a phosphor storage plate. After exposure, the plate is scanned with a laser and a digital, quantitative image can be reconstituted. To demonstrate the concept, three types of microstructures suited for integration in chemical analysis systems were imaged with C-11- and Ga-68-labeled tracers. The influence of factors such as geometry of the object and type of radionuclide on resolution and sensitivity was investigated. The resolution ranged from 0.9 to 2.7 mm (fwhm). Measuring low amounts of radioactivity in the three structures, 2-20 Bq could be detected, which corresponded to 2.3-500 amol or 2.4-110 pM tracer. The imaging approach was applied to study analyte concentration and sample dilution effects on the performance of a capillary extraction column integrated in an automated LC-ESI-MS system. The utility of the technique was further illustrated by imaging of microchannels in a zeonor plastic compact disk and in a poly(dimethylsiloxane) material for the study of nonspecific peptide adsorption.

    National Category
    Analytical Chemistry
    Identifiers
    urn:nbn:se:uu:diva-92493 (URN)10.1021/ac040070e (DOI)
    Available from: 2005-01-11 Created: 2005-01-11 Last updated: 2017-12-14Bibliographically approved
    5. Imaging of peptide adsorption to microfluidic channels in a plastic compact disc using a positron emitting radionuclide
    Open this publication in new window or tab >>Imaging of peptide adsorption to microfluidic channels in a plastic compact disc using a positron emitting radionuclide
    Show others...
    In: Lab on a ChipArticle in journal (Refereed) Submitted
    Identifiers
    urn:nbn:se:uu:diva-92494 (URN)
    Available from: 2005-01-11 Created: 2005-01-11 Last updated: 2014-03-03Bibliographically approved
  • 32.
    Lavén, Martin
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry, Analytical Chemistry.
    Wallenborg, Susanne
    Velikyan, Irina
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry, Organic Chemistry.
    Bergström, Sara
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry, Analytical Chemistry.
    Djodjic, Majda
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry, Analytical Chemistry.
    Ljung, Jenny
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry, Analytical Chemistry.
    Berglund, Oskar
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry, Analytical Chemistry.
    Edenwall, Niklas
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry, Analytical Chemistry.
    Markides, Karin E.
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry, Analytical Chemistry.
    Långström, Bengt
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry, Organic Chemistry.
    Radionuclide Imaging of Miniaturized Chemical Analysis Systems2004In: Analytical Chemistry, ISSN 0003-2700, E-ISSN 1520-6882, Vol. 76, no 23, p. 7102-7108Article in journal (Refereed)
    Abstract [en]

    We propose radionuclide imaging as a valuable tool for the study of molecular interactions in miniaturized systems for chemical analysis. Sensitive and quantitative imaging can be performed with compounds labeled with short-lived positron-emitting radionuclides, such as C-11 and Ga-68, within selected parts of the system. Radionuclide imaging is not restricted to transparent materials since the relatively energetic positrons can penetrate high optical density materials. Experimentally, a radiotracer is introduced into the object of study, which is subsequently placed on a phosphor storage plate. After exposure, the plate is scanned with a laser and a digital, quantitative image can be reconstituted. To demonstrate the concept, three types of microstructures suited for integration in chemical analysis systems were imaged with C-11- and Ga-68-labeled tracers. The influence of factors such as geometry of the object and type of radionuclide on resolution and sensitivity was investigated. The resolution ranged from 0.9 to 2.7 mm (fwhm). Measuring low amounts of radioactivity in the three structures, 2-20 Bq could be detected, which corresponded to 2.3-500 amol or 2.4-110 pM tracer. The imaging approach was applied to study analyte concentration and sample dilution effects on the performance of a capillary extraction column integrated in an automated LC-ESI-MS system. The utility of the technique was further illustrated by imaging of microchannels in a zeonor plastic compact disk and in a poly(dimethylsiloxane) material for the study of nonspecific peptide adsorption.

  • 33.
    Liljegren, G.
    et al.
    Uppsala University, Teknisk-naturvetenskapliga vetenskapsområdet, Chemistry, Department of Chemistry.
    Pettersson, J.
    Markides, K.E.
    Nyholm, L.
    Electrochemical solid-phase microextraction of anions and cations using polypyrrole coatings and an integrated three-electrode device2002In: The Analyst, no 127, p. 591-597Article in journal (Refereed)
  • 34.
    Liljegren, Gustav
    Uppsala University, Teknisk-naturvetenskapliga vetenskapsområdet, Chemistry, Department of Chemistry.
    Development and Investigations of Novel Sample Preparation Techniques: Electrochemical Extraction and Evaluation of Miniaturized Analytical Devices Coupled to Mass Spectrometry2005Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    Different sample preparation steps prior to a detection method are often essential in analytical chemistry. In this thesis, both static extractions and on-line coupled solid-phase extractions have been studied in combination with different detection techniques. Aspects of performing sample preparations in miniaturized analytical devices and the development of poly(dimethylsiloxane) (PDMS) microchips are discussed. Polypyrrole was also evaluated as an electrochemically controllable stationary phase for solid-phase microextraction (SPME) and solid-phase extraction (SPE).

    The first part of this thesis describes the extraction of an organic compound from a very complex solid matrix utilizing the pressurized-fluid extraction (PFE) technique. The presented results show that PFE is easily optimized and enables rapid extractions and extracts relatively free from interferences.

    An integrated three-electrode device, which enabled electrochemical (EC) SPME under potential control, was developed. With this device, both anions and cations could be extracted employing two types of polypyrrole films. Planar micro band electrodes positioned at the end of a capillary were also used to electrochemically extract and detect anions in a miniaturized flow system. Different analyte concentrations and preconcentration times were examined, and good linear correlations were found between the extraction time and the detection response. The on-line coupling of a thin layer EC cell, with a polypyrrole coated working electrode, to different mass spectrometric (MS) techniques is also described and evaluated. The results show that EC-SPE, employing polypyrrole as stationary phase, can be used as a preconcentration step prior to detection.

    In addition, this thesis describes the development and on-line coupling of a microelectrode array equipped PDMS microchip with an integrated graphite electrospray emitter to electrospray ionization (ESI) MS. The system enabled short transfer times and an EC conversion efficiency of 30% at a flow rate of 0.5 μL/min. The on-line EC/ESI-MS experiments were significantly simplified using a wireless Bluetooth battery-powered EC instrument.

    List of papers
    1. Pressurized-fluid extraction of chlorinated paraffins from the biodegradable fraction of source-separated household waste
    Open this publication in new window or tab >>Pressurized-fluid extraction of chlorinated paraffins from the biodegradable fraction of source-separated household waste
    Show others...
    2001 In: Fresenius Journal of Analytical Chemistry, ISSN 0937-0633, Vol. 370, no 7, p. 913-918Article in journal (Refereed) Published
    Identifiers
    urn:nbn:se:uu:diva-93081 (URN)
    Available from: 2005-05-03 Created: 2005-05-03Bibliographically approved
    2. Electrochemical solid-phase microextraction of anions and cations using polypyrrole coatings and an integrated three-electrode device
    Open this publication in new window or tab >>Electrochemical solid-phase microextraction of anions and cations using polypyrrole coatings and an integrated three-electrode device
    2002 In: The Analyst, ISSN 0003-2654, Vol. 127, no 5, p. 591-597Article in journal (Refereed) Published
    Identifiers
    urn:nbn:se:uu:diva-93082 (URN)
    Available from: 2005-05-03 Created: 2005-05-03Bibliographically approved
    3. Electrochemically controlled solid-phase microextraction and preconcentration using polypyrrole coated microarray electrodes in a flow system
    Open this publication in new window or tab >>Electrochemically controlled solid-phase microextraction and preconcentration using polypyrrole coated microarray electrodes in a flow system
    2003 In: The Analyst, ISSN 0003-2654, Vol. 128, no 3, p. 232-236Article in journal (Refereed) Published
    Identifiers
    urn:nbn:se:uu:diva-93083 (URN)
    Available from: 2005-05-03 Created: 2005-05-03Bibliographically approved
    4. Capillary electrophoresis coupled to mass spectrometry from a polymer modified poly(dimethylsiloxane) microchip with an integrated graphite electrospray tip
    Open this publication in new window or tab >>Capillary electrophoresis coupled to mass spectrometry from a polymer modified poly(dimethylsiloxane) microchip with an integrated graphite electrospray tip
    Show others...
    2005 (English)In: The Analyst, ISSN 0003-2654, E-ISSN 1364-5528, Vol. 130, no 2, p. 193-199Article in journal (Refereed) Published
    Abstract [en]

    Hybrid capillary-poly(dimethysiloxane) (PDMS) microchips with integrated electrospray ionization (ESI) tips were directly fabricated by casting PDMS in a mould. The shapes of the emitter tips were drilled into the mould, which produced highly reproducible three-dimensional tips. Due to the fabrication method of the microfluidic devices, no sealing was necessary and it was possible to produce a perfect channel modified by PolyE-323, an aliphatic polyamine coating agent. A variety of different coating procedures were also evaluated for the outside of the emitter tip. Dusting graphite on a thin unpolymerised PDMS layer followed by polymerisation was proven to be the most suitable procedure. The emitter tips showed excellent electrochemical properties and durabilities. The coating of the emitter was eventually passivated, but not lost, and could be regenerated by electrochemical means. The excellent electrochemical stability was further confirmed in long term electrospray experiments, in which the emitter sprayed continuously for more than 180 h. The PolyE-323 was found suitable for systems that integrate rigid fused silica and soft PDMS technology, since it simply could be applied successfully to both materials. The spray stability was confirmed from the recording of a total ion chromatogram in which the electrospray current exhibited a relative standard deviation of 3.9% for a 30 min run. CE-ESI-MS separations of peptides were carried out within 2 min using the hybrid PDMS chip resulting in similar efficiencies as for fused silica capillaries of the same length and thus with no measurable band broadening effects, originating from the PDMS emitter.

    National Category
    Analytical Chemistry Inorganic Chemistry
    Identifiers
    urn:nbn:se:uu:diva-93084 (URN)10.1039/b414592e (DOI)15665973 (PubMedID)
    Available from: 2005-05-03 Created: 2005-05-03 Last updated: 2017-12-14Bibliographically approved
    5. On-line electrochemically controlled solid-phase extraction coupled to electrospray and inductively coupled plasma mass spectrometry
    Open this publication in new window or tab >>On-line electrochemically controlled solid-phase extraction coupled to electrospray and inductively coupled plasma mass spectrometry
    Show others...
    Manuscript (Other academic)
    Identifiers
    urn:nbn:se:uu:diva-93085 (URN)
    Available from: 2005-05-03 Created: 2005-05-03 Last updated: 2010-01-13Bibliographically approved
    6. On-line coupling of a microelectrode array equipped poly(dimethylsiloxane) microchip with an integrated graphite electrospray emitter to electrospray ionisation mass spectrometry
    Open this publication in new window or tab >>On-line coupling of a microelectrode array equipped poly(dimethylsiloxane) microchip with an integrated graphite electrospray emitter to electrospray ionisation mass spectrometry
    Show others...
    Manuscript (Other academic)
    Identifiers
    urn:nbn:se:uu:diva-93086 (URN)
    Available from: 2005-05-03 Created: 2005-05-03 Last updated: 2011-03-21
  • 35.
    Lindblom, Torbjörn
    Uppsala University, Teknisk-naturvetenskapliga vetenskapsområdet, Chemistry, Department of Chemistry, Analytical Chemistry.
    Reactions in the System Nitro-cellulose/ Diphenylamine with Special Reference to the Formation of a Stabilizing Product Bonded to Nitro-cellulose2004Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    The methods HPLC, microcalorimetry and FTIR together with chemometry, provide good analytical tools to follow the degradation of nitro-cellulose.

    The degradation products formed from diphenylamine (DPA) during storage can be followed with HPLC. FTIR, together with chemometry, also gives the precision needed for safety control of propellants.

    Nitro-cellulose (NC) containing DPA obtained a green colour already after 1 day storage at 70°C. About 10% of the stabilizer, and its derivatives, added were not extractable giving an extended time to autocatalysis. This time could be extended up to 70 days at 70°C for an extracted sample compared to about 3 days for non-stabilized NC. This was not shown before.

    Aged and extracted NC samples contained a non-extractable nitro compound. The most likely compound is 2,4´-dinitroDPA, probably bonded to NC via the amine nitrogen. The bonding to NC occurs after the formation of NNODPA. This is something not described before.

    Using another batch of nitro-cellulose to find out if a chemical bonding occurs gave inconclusive results as a blue NC was formed. Low molecular NC with high stability was obtained. A chemical bonding probably occurs when using NNODPA as a stabilizer, indicating NNODPA plays a key role.

    The use of FTIR/chemometry is a promising method to use when studying small chemical changes. The described methodology should be used to find out more about the compound(s) being bonded to NC.

    List of papers
    1. Comparison and evaluation of modern analytical methods used for stability testing of a single base propellant
    Open this publication in new window or tab >>Comparison and evaluation of modern analytical methods used for stability testing of a single base propellant
    1985 In: Symposium on Chemical Problems Connected with the Stability of Explosives, ISSN 0348-7180, Vol. 7, p. 247-269Article in journal (Refereed) Published
    Identifiers
    urn:nbn:se:uu:diva-91331 (URN)
    Available from: 2004-03-31 Created: 2004-03-31Bibliographically approved
    2. Irreversible absorption of diphenylamine onto a straight phase and a reversed phase HPLC-column
    Open this publication in new window or tab >>Irreversible absorption of diphenylamine onto a straight phase and a reversed phase HPLC-column
    1992 In: Symposium on Chemical Problems Connected with the Stability of Explosives, ISSN 0348-7180, Vol. 9, p. 205-213Article in journal (Refereed) Published
    Identifiers
    urn:nbn:se:uu:diva-91332 (URN)
    Available from: 2004-03-31 Created: 2004-03-31Bibliographically approved
    3. Degradation of Nitro-cellulose. Some Microcalorimetric Studies
    Open this publication in new window or tab >>Degradation of Nitro-cellulose. Some Microcalorimetric Studies
    1992 In: Symposium on Chemical Problems Connected with the Stability of Explosives, ISSN 0348-7180, Vol. 9, p. 69-75Article in journal (Refereed) Published
    Identifiers
    urn:nbn:se:uu:diva-91333 (URN)
    Available from: 2004-03-31 Created: 2004-03-31Bibliographically approved
    4. Quantitative determination of stabiliser in a single base propellant by chemometric analysis of Fourier transform infrared spectra
    Open this publication in new window or tab >>Quantitative determination of stabiliser in a single base propellant by chemometric analysis of Fourier transform infrared spectra
    1995 In: Chemometrics and intelligent laboratory systems, ISSN 0169-7439, Vol. 29, p. 243-254Article in journal (Refereed) Published
    Identifiers
    urn:nbn:se:uu:diva-91334 (URN)
    Available from: 2004-03-31 Created: 2004-03-31Bibliographically approved
    5. Reactions in stabilizer and between stabilizer and nitro-cellulose
    Open this publication in new window or tab >>Reactions in stabilizer and between stabilizer and nitro-cellulose
    2002 In: Propellants, Explosives, Pyrotechnics, ISSN 0721-3115, Vol. 27, no 4, p. 197-208Article in journal (Refereed) Published
    Identifiers
    urn:nbn:se:uu:diva-91335 (URN)
    Available from: 2004-03-31 Created: 2004-03-31Bibliographically approved
  • 36. Lindegårdh, N.
    et al.
    Ashton, M.
    Bergqvist, Y.
    Uppsala University, Teknisk-naturvetenskapliga vetenskapsområdet, Chemistry, Department of Chemistry.
    Automated Solid-Phase Extraction Method for the Determination of Piperaquine in Plasma by Peak Compression Liquid Chromatography2003In: J. of Chromatographic Science, no 40, p. 44-49Article in journal (Refereed)
  • 37.
    Lindegårdh, N.
    et al.
    Uppsala University, Teknisk-naturvetenskapliga vetenskapsområdet, Chemistry, Department of Chemistry.
    Forslund, M.
    Green, M.D.
    Kaneko, A.
    Bergqvist, Y.
    Automated Solid-Phase Extraction for Determination of Amodiaquine, Chloroquine and Metabolites in Capillary Blood on Sampling Paper by Liquid Chromatography2002In: Chromatographia, no 55, p. 5-12Article in journal (Refereed)
  • 38.
    Lindegårdh, Niklas
    Uppsala University, Teknisk-naturvetenskapliga vetenskapsområdet, Chemistry, Department of Chemistry, Analytical Chemistry.
    Development of Field-adapted Analytical Methods for the Determination of New Antimalarial Drugs in Biological Fluids2003Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    This thesis deals with the development of analytical methods for the determination of new antimalarial drugs in biological fluids. The goal was to develop methods that facilitate clinical studies performed in the field, such as capillary blood sampling onto sampling paper.

    Methods for the determination of atovaquone (ATQ) in plasma, whole blood and capillary blood applied onto sampling paper were developed and validated.

    Automated solid-phase extraction (SPE) and liquid chromatography (LC) with UV absorbance detection was used to quantify ATQ. Venous blood contained higher levels of ATQ than capillary blood after a single dose of Malarone (ATQ + proguanil).

    Ion-pairing LC was used to separate amodiaquine (AQ), chloroquine (CQ) and their metabolites on a CN-column. A method for quantification of AQ, CQ and their metabolites in capillary blood applied onto sampling paper was developed and validated. Perchloric acid and acetonitrile were used to facilitate the extraction of the analytes from the sampling paper. The liquid extract was further cleaned by SPE.

    Methods for the determination of piperaquine (PQ) in plasma and whole blood using SPE and LC were developed and validated. Addition of trichloroacetic acid (TCA) to the samples prior to injection into the LC-system significantly enhanced the efficiency for the PQ peak. Serum and whole blood contained higher levels (about 300 nM) of PQ than plasma (about 200 nM) after a single oral dose of 340 mg PQ. This indicates that PQ may be taken up in the leucocytes and thrombocytes.

    List of papers
    1. Automated solid-phase extraction method for the determination of atovaquone in plasma and whole blood by rapid high-performance liquid chromatography
    Open this publication in new window or tab >>Automated solid-phase extraction method for the determination of atovaquone in plasma and whole blood by rapid high-performance liquid chromatography
    2000 In: Journal of chromatography B, Vol. 744, p. 9-17Article in journal (Refereed) Published
    Identifiers
    urn:nbn:se:uu:diva-90188 (URN)
    Available from: 2003-04-24 Created: 2003-04-24Bibliographically approved
    2. Automated solid-phase extraction method for the determination of atovaquone in capillary blood applied onto sampling paper by rapid high-performance liquid chromatography
    Open this publication in new window or tab >>Automated solid-phase extraction method for the determination of atovaquone in capillary blood applied onto sampling paper by rapid high-performance liquid chromatography
    2001 In: Journal of chromatography B, Vol. 758, p. 137-144Article in journal (Refereed) Published
    Identifiers
    urn:nbn:se:uu:diva-90189 (URN)
    Available from: 2003-04-24 Created: 2003-04-24Bibliographically approved
    3. Automated solid-phase extraction method for the determination of amodiaquine, chloroquine and their metabolites in capillary blood applied onto sampling paper by high-performance liquid chromatography
    Open this publication in new window or tab >>Automated solid-phase extraction method for the determination of amodiaquine, chloroquine and their metabolites in capillary blood applied onto sampling paper by high-performance liquid chromatography
    Show others...
    2002 In: Chromatographia, Vol. 55, p. 5-12Article in journal (Refereed) Published
    Identifiers
    urn:nbn:se:uu:diva-90190 (URN)
    Available from: 2003-04-24 Created: 2003-04-24Bibliographically approved
    4. Automated solid-phase extraction method for the determination of piperaquine in plasma by peak compression liquid chromatography
    Open this publication in new window or tab >>Automated solid-phase extraction method for the determination of piperaquine in plasma by peak compression liquid chromatography
    2003 In: Journal of chromatographic science, Vol. 41, no 1, p. 44-49Article in journal (Refereed) Published
    Identifiers
    urn:nbn:se:uu:diva-90191 (URN)
    Available from: 2003-04-24 Created: 2003-04-24Bibliographically approved
    5. Automated solid-phase extraction method for the determination of piperaquine in whole blood by rapid liquid chromatography
    Open this publication in new window or tab >>Automated solid-phase extraction method for the determination of piperaquine in whole blood by rapid liquid chromatography
    2003 (English)In: Therapeutic Drug Monitoring, ISSN 0163-4356, E-ISSN 1536-3694, Vol. 25, no 5, p. 544-551Article in journal (Refereed) Published
    Abstract [en]

    A bioanalytic method for the determination of piperaquine in whole blood by solid-phase extraction and rapid liquid chromatography has been developed and validated. Whole blood was hemolyzed with deionized water, and an internal standard was added to the samples before they were loaded onto a PRS cation-exchange solid-phase extraction column. Piperaquine and internal standard were analyzed by liquid chromatography on a Chromolith Performance (100 x 4.6 mm) column with mobile phase acetonitrile:phosphate buffer, I = 0.1, pH 2.5 (8:92, vol/vol), flow rate 4 mL x min-1, and UV detection at 345 nm. The intraassay precision for whole blood was 3.2% at 3.00 microM and 12.3% at 0.100 microM. The interassay precision for whole blood was 1.8% at 3.00 microM and 5.2% at 0.100 microM. The lower limit of quantification and the limit of detection were 0.050 microM and 0.010 microM, respectively.

    National Category
    Natural Sciences
    Identifiers
    urn:nbn:se:uu:diva-90192 (URN)14508376 (PubMedID)
    Available from: 2003-04-24 Created: 2003-04-24 Last updated: 2017-12-14Bibliographically approved
    6. Time-dependent pharmacokinetics and drug metabolism of atovaquone plus proguanil (Malarone) when taken as chemoprophylaxis
    Open this publication in new window or tab >>Time-dependent pharmacokinetics and drug metabolism of atovaquone plus proguanil (Malarone) when taken as chemoprophylaxis
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    2002 In: European journal of clinical pharmacology, Vol. 58, p. 19-27Article in journal (Refereed) Published
    Identifiers
    urn:nbn:se:uu:diva-90193 (URN)
    Available from: 2003-04-24 Created: 2003-04-24Bibliographically approved
  • 39.
    Moberg, M.
    et al.
    Uppsala University, Teknisk-naturvetenskapliga vetenskapsområdet, Chemistry, Department of Chemistry.
    Holmström, S.J.M.
    Lundström, U.S.
    Markides, K.E.
    Novel approach to the determination of structurally similar hydroxamate siderophores by column-switching capillary liquid chromatography coupled to mass spectrometry2003In: J. of Chromatography A, no 1020, p. 91-97Article in journal (Refereed)
  • 40.
    Nilsson, Eva
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry, Analytical Chemistry.
    Coupled Liquid Separation and Spectrometric Detection of Organic Compounds Containing Hetero-atoms2004Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    This thesis exemplifies the strength in the combination of inductively coupled plasma (ICP) spectrometry and electrospray ionization tandem mass spectrometry ESI-MS/MS as detection techniques for liquid chromatography (LC) in the search for and investigation of compounds that bind or can bind hetero-atoms. Furthermore, some aspects involved in the coupling of LC and ICP spectrometry and quantification without identical standards have been studied.

    The importance of using a separation step in combination with ICP spectrometry was shown for urine and blood plasma samples from patients treated with boron neutron capture therapy. In addition to the carrier molecule used in the therapy, one major and a few possible minor metabolites were found in the urine samples. One fragment mass of the major metabolite was obtained with LC-ESI-MS/MS. Liquid chromatography coupled to ICP-MS was also shown to be a valuable tool for fingerprinting metal-binding compounds in complex matrices, such as siderophores (iron-complexing compounds) in soil. The presence of at least two siderophores in a field soil solution sample could be revealed by LC-ICP-MS. Their identities could thereafter be determined by LC-ESI-MS/MS.

    The non-UV-absorbing o-carboranylalanine could be quantified in relation to its degradation products by LC-ICP-AES, which provided information about the mechanism behind the degradation. Moreover, LC-ICP spectrometry was shown to provide an accurate quantification of biomolecules (bias < 10 %) when evaluated from external calibration graphs based on inorganic elemental standards.

    Finally, the causes of the large decrease in boron signal seen when adding acetonitrile to the LC mobile phase in LC-ICP-MS was investigated in some detail. Space charge effects might explain a large part of the depression from carbon species on the boron signal.

    List of papers
    1. Determination of boron containing compounds in urine and blood plasma from boron neutron capture therapy patients: The importance of using coupled techniques
    Open this publication in new window or tab >>Determination of boron containing compounds in urine and blood plasma from boron neutron capture therapy patients: The importance of using coupled techniques
    2002 In: Anal. Chem., Vol. 74, no 20, p. 5358-5363Article in journal (Refereed) Published
    Identifiers
    urn:nbn:se:uu:diva-91312 (URN)
    Available from: 2004-01-30 Created: 2004-01-30Bibliographically approved
    2. Fingerprinting metal-containing biomolecules after reductive displacement of iron by gallium and subsequent column-switched LC-ICPMS analysis applied on siderophores
    Open this publication in new window or tab >>Fingerprinting metal-containing biomolecules after reductive displacement of iron by gallium and subsequent column-switched LC-ICPMS analysis applied on siderophores
    Show others...
    2004 (English)In: Analytical Chemistry, ISSN 0003-2700, E-ISSN 1520-6882, Vol. 76, no 9, p. 2618-2622Article in journal (Refereed) Published
    Abstract [en]

    Column-switching liquid chromatography followed by low-resolution ICPMS was evaluated as a tool for speciation analysis of metal-containing biomolecules. The strategy was applied on siderophores, strong iron chelators of low molecular weight (M(w) < 1500). Prior to the LC-ICPMS analysis, reductive displacement of iron by gallium was performed using ascorbate as the reducing agent to increase the sensitivity. Different experimental conditions during the exchange reaction were tested using ferrichrysin and ferrichrome for evaluation. A reaction time of 30 min and a pH of 3.9 gave an exchange yield of 27 and 83% for ferrichrysin and ferrichrome, respectively. A gradient elution profile was also developed to separate gallium-chelated siderophores on a PGC column. Detection limits for standard solutions of ferrichrysin and ferrichrome in the low-nanomolar range were obtained by monitoring the gallium-69 isotope. The combined use of LC-ICPMS and LC-ESI-MS/MS was also evaluated as a tool to identify unknown metal complexes, here siderophores, in field soil solution samples.

    National Category
    Chemical Sciences
    Identifiers
    urn:nbn:se:uu:diva-94665 (URN)10.1021/ac0355000 (DOI)15117206 (PubMedID)
    Available from: 2006-08-30 Created: 2006-08-30 Last updated: 2017-12-14Bibliographically approved
    3. A kinetic study of the self-degradation of o-carboranylalanine to nido-carboranylalanine in solution
    Open this publication in new window or tab >>A kinetic study of the self-degradation of o-carboranylalanine to nido-carboranylalanine in solution
    Show others...
    1999 In: Acta Chem. Scand., Vol. 53, no 9, p. 731-736Article in journal (Refereed) Published
    Identifiers
    urn:nbn:se:uu:diva-91314 (URN)
    Available from: 2004-01-30 Created: 2004-01-30Bibliographically approved
    4. The use of inorganic elemental standards in the quantification of proteins and biomolecular compounds by inductively coupled plasma spectrometry
    Open this publication in new window or tab >>The use of inorganic elemental standards in the quantification of proteins and biomolecular compounds by inductively coupled plasma spectrometry
    2002 In: J. Anal. At. Spectrom, Vol. 17, no 5, p. 491-496Article in journal (Refereed) Published
    Identifiers
    urn:nbn:se:uu:diva-91315 (URN)
    Available from: 2004-01-30 Created: 2004-01-30Bibliographically approved
    5. Matrix effects of organic solvents in the determination of boron containing compounds by ICP-MS
    Open this publication in new window or tab >>Matrix effects of organic solvents in the determination of boron containing compounds by ICP-MS
    Show others...
    Manuscript (Other academic)
    Identifiers
    urn:nbn:se:uu:diva-91316 (URN)
    Available from: 2004-01-30 Created: 2004-01-30 Last updated: 2010-01-13Bibliographically approved
  • 41.
    Nilsson, S
    et al.
    Uppsala University, Teknisk-naturvetenskapliga vetenskapsområdet, Chemistry, Department of Chemistry.
    Klett, O
    Uppsala University, Teknisk-naturvetenskapliga vetenskapsområdet, Technology, Department of Engineering Sciences.
    Svedberg, M
    Amirkhani, A
    Nyholm, L
    Gold-coated fused-silica sheathless electrospray emitters based on vapor-deposited titanium adhesion layers2003In: Rapid communications in mass spectrometry, Vol. 17, p. 1535-1540Article in journal (Refereed)
  • 42.
    Nilsson, Stefan
    Uppsala University, Teknisk-naturvetenskapliga vetenskapsområdet, Chemistry, Department of Chemistry.
    Development of Sheathless Electrospray Mass Spectrometry and Investigations of Associated Electrochemical Processes – A Fairy Tale2004Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    In microscale separations, such as capillary electrophoresis and -liquid chromatography, the liquid flow rates are in the order of nanoliters per second. If such flow rates are to be interfaced with a mass spectrometer (MS) using electrospray (ES) ionization, without loss of separation efficiency, each fraction of the analyte zone must remain undisturbed by the high voltage contact necessary for ES. One design that accomplishes this is the pure sheathless approach, where a thin, vapor deposited metal film covers the outside of the electrospray emitter tip.

    This thesis describes the development of such sheathless emitters. The lifetimes of polymer embedded gold (“fairy dust”) or graphite (“black dust”) emitters were shown to by far exceed those of previously used conductive films. In addition, the production of emitters with these coatings was substantially simplified. The increase in durability was found to be due to enhanced resistance towards the electrochemical processes associated with ES. In analogy, the reasons for the limited durability of previously used methods were correlated with their tendency to oxidize, or be mechanically removed, during electrochemical reactions.

    Electrochemical processes associated with the electrospray potential were also found to seriously disturb analyses in which porous graphitic carbon was used as the separation medium. A proper choice of grounding point locations eliminated these disturbances.

    At last, the differences regarding analytical performance of several sheathless interface configurations, used in capillary liquid chromatography, were examined. The best performance was obtained when a pure sheathless emitter with a conductive layer of polyimide and graphite was coupled to the LC column through a Teflon sleeve.

    List of papers
    1. Metallized sheathless electrospray emitters for use in capillary electrophoresis orthogonal time-of-flight mass spectrometry
    Open this publication in new window or tab >>Metallized sheathless electrospray emitters for use in capillary electrophoresis orthogonal time-of-flight mass spectrometry
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    1999 In: Rapid Communications in Mass Spectrometry, ISSN 0951-4198, Vol. 13, no 11, p. 994-1002Article in journal (Refereed) Published
    Identifiers
    urn:nbn:se:uu:diva-91879 (URN)
    Available from: 2004-05-25 Created: 2004-05-25Bibliographically approved
    2. A design for low-flow sheathless electrospray emitters
    Open this publication in new window or tab >>A design for low-flow sheathless electrospray emitters
    1999 In: Analytical Chemistry, ISSN 0003-2700, Vol. 71, no 19, p. 4115-4118Article in journal (Refereed) Published
    Identifiers
    urn:nbn:se:uu:diva-91880 (URN)
    Available from: 2004-05-25 Created: 2004-05-25Bibliographically approved
    3. MS detection for microseparation techniques
    Open this publication in new window or tab >>MS detection for microseparation techniques
    1999 In: Chimia, ISSN 0009-4293, Vol. 53, no 10, p. 506-510Article in journal (Refereed) Published
    Identifiers
    urn:nbn:se:uu:diva-91881 (URN)
    Available from: 2004-05-25 Created: 2004-05-25Bibliographically approved
    4. On-column conductive coating for thermolabile columns used in capillary zone electrophoresis sheathless electrospray ionization mass spectrometry
    Open this publication in new window or tab >>On-column conductive coating for thermolabile columns used in capillary zone electrophoresis sheathless electrospray ionization mass spectrometry
    2000 In: Rapid Communications in Mass Spectrometry, ISSN 0951-4198, Vol. 14, no 1, p. 6-11Article in journal (Refereed) Published
    Identifiers
    urn:nbn:se:uu:diva-91882 (URN)
    Available from: 2004-05-25 Created: 2004-05-25Bibliographically approved
    5. Sheathless electrospray from polymer microchips
    Open this publication in new window or tab >>Sheathless electrospray from polymer microchips
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    2003 In: Analytical Chemistry, ISSN 0003-2700, Vol. 75, no 15, p. 3934-3940Article in journal (Refereed) Published
    Identifiers
    urn:nbn:se:uu:diva-91883 (URN)
    Available from: 2004-05-25 Created: 2004-05-25 Last updated: 2011-03-21
    6. A simple and robust conductive graphite coating for sheathless electrospray emitters used in capillary electrophoresis/mass spectrometry
    Open this publication in new window or tab >>A simple and robust conductive graphite coating for sheathless electrospray emitters used in capillary electrophoresis/mass spectrometry