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  • 1.
    Abrahamsson, Maria
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, För teknisk-naturvetenskapliga fakulteten gemensamma enheter, Accelerator mass spectrometry group. Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Physical Chemistry.
    Wolpher, Henriette
    Johansson, Olof
    Larsson, Jan
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Physical Chemistry.
    Kritikos, Mikael
    Eriksson, Lars
    Norrby, Per-Ola
    Bergquist, Jonas
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry, Analytical Chemistry.
    Sun, Licheng
    Åkermark, Björn
    Hammarström, Leif
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Physical Chemistry.
    A New Strategy for the Improvement of Photophysical Properties in Ruthenium(II) Polypyridyl Complexes: Synthesis and Photophysical and Electrochemical Characterization of Six Mononuclear Ruthenium(II) Bisterpyridine-Type Complexes2005In: Inorganic Chemistry, ISSN 0020-1669, E-ISSN 1520-510X, Vol. 44, no 9, p. 3215-3225Article in journal (Refereed)
  • 2.
    Ahlgren, Joakim
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry, Analytical Chemistry.
    Tranvik, Lars
    Gogoll, Adolf
    Waldebäck, Monica
    Markides, Karin
    Rydin, Emil
    Depth attenuation of biogenic phosphorus compounds in lake sediment measured by 31P NMR2005In: Environmental Science and Technology, ISSN 0013-936, Vol. 39, no 3, p. 867-872Article in journal (Refereed)
  • 3.
    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.

  • 4.
    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
    Show others...
    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
    Show others...
    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
    Show others...
    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
    Show others...
    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
  • 5.
    Amirkhani, Ardeshir
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry, Analytical Chemistry.
    Heldin, Eva
    Markides, Karin E.
    Bergquist, Jonas
    Quantitation of tryptophan, kynurenine and kynurenic acid in human plasma by capillary liquid chromatography - electrospray2002In: Journal of Chromatography B, Vol. 780, no 2, p. 381-387Article in journal (Refereed)
  • 6.
    Amirkhani, Ardeshir
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry, Analytical Chemistry.
    Rajda, Cecilia
    Arvidsson, Björn
    Bencsik, Krisztina
    Boda, Krisztina
    Seres, Erika
    Markides, Karin E.
    Vecsei, Laszlo
    Bergquist, Jonas
    Beta-interferon effects the tryptophan metabolism in the plasma of multiple sclerosis patientsManuscript (Other academic)
  • 7.
    Amirkhani, Ardeshir
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry, Analytical Chemistry.
    Rajda, Cecilia
    Arvidsson, Björn
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry, Analytical Chemistry.
    Bencsik, Krisztina
    Boda, Krisztina
    Seres, Erika
    Markides, Karin E.
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry, Analytical Chemistry.
    Vecsei, Laszlo
    Bergquist, Jonas
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry, Analytical Chemistry.
    Interferon-beta affects the tryptophan metabolism in multiple sclerosis patients2005In: European Journal of Neurology, ISSN 1351-5101, E-ISSN 1468-1331, Vol. 12, no 8, p. 625-631Article in journal (Refereed)
    Abstract [en]

    Tryptophan and its metabolites are of great interest in understanding the pathogenesis of multiple sclerosis (MS). The total levels of tryptophan and its metabolites, kynurenine and kynurenic acid were determined in plasma by capillary liquid chromatography electrospray ionisation tandem mass spectrometry. This is the first report of the plasma levels of these analytes in healthy controls and relapsing-remitting MS patients receiving long-term and acute interferon-beta (IFN-beta) treatment. Twenty-four hours post-administration increased kynurenine levels (first IFN MS versus healthy, P = 0.042) and kynurenine/tryptophan ratio (K/T; first IFN MS versus healthy, P =0.027; first IFN MS versus long-term IFN MS, P = 0.036) were found. The long-term IFN MS group had higher K/T ratios at 4 and 12 h post-administration (P = 0.015 and 0.009, respectively). The increase of K/T ratio in the first IFN MS group indicate an induction of the enzyme indolamine-2,3-dioxygenase (IDO), as reported earlier in experimental allergic encephalomyelitis. As IDO is participating in both inflammatory and neurodegenerative processes, further knowledge of its involvement in the pathogenesis of MS is of great importance.

  • 8.
    Amirkhani, Ardeshir
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry, Analytical Chemistry.
    Wetterhall, Magnus
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry, Analytical Chemistry.
    Nilsson, Stefan
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry, Analytical Chemistry.
    Danielsson, Rolf
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry, Analytical Chemistry.
    Bergquist, Jonas
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry, Analytical Chemistry.
    Comparison between different sheathless electrospray emitter configurations regarding the performance of nanoscale liquid chromatography time-of-flight mass spectrometry analysis2004In: Journal of Chromatography A, ISSN 0021-9673, E-ISSN 1873-3778, Vol. 1033, no 2, p. 257-266Article in journal (Refereed)
    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.

  • 9.
    Andersson, Marit
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry, Analytical Chemistry.
    Olin, Åke
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry, Analytical Chemistry.
    A modified standard addition method in X-ray fluorescence spectrometry1993In: Talanta: The International Journal of Pure and Applied Analytical Chemistry, ISSN 0039-9140, E-ISSN 1873-3573, Vol. 40, no 5, p. 669-674Article in journal (Refereed)
    Abstract [en]

    A modified standard addition method for single element determination by X-ray fluorescence spectrometry has been studied. The attenuation properties of the standard added samples are kept constant by adding decreasing amounts of an attenuation modifier along with increasing amounts of a standard. In this way the standard addition curve will be a straight line in cases where the ordinary standard addition curve is non-linear, and linear regression can be used to evaluate the concentration of the analyte. Standard additions of oxides of a number of elements, with and without modifier, have been made to cellulose powder or a mixture of aluminium oxide and polyethylene as matrices in order to test the method. The method has been applied to the determination of zinc in fly-ash from a steel work and of iron in cement. The fly-ash contained about 5% of zinc and the cement samples between 2 and 5% of Fe(2)O(3). The results were compared with those obtained by ICP-AES after decomposition of samples in lithium tetraborate or lithium metaborate and dissolution of the melt in 10%(v/v) nitric acid. The results agreed within 2%, relative, for fly-ash and within 3-6%, relative, for cement samples.

  • 10.
    Andersson, Marit
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry, Analytical Chemistry.
    Olin, Åke
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry, Analytical Chemistry.
    Determination of lead in household refuse fly-ash by X-ray fluorescence spectrometry and a modified standard-addition technique1991In: Talanta: The International Journal of Pure and Applied Analytical Chemistry, ISSN 0039-9140, E-ISSN 1873-3573, Vol. 38, no 4, p. 385-390Article in journal (Refereed)
    Abstract [en]

    Lead in fly-ash from a garbage incinerator has been determined by X-ray fluorescence spectrometry (XRFS) and a modified standard-addition method. To keep the attenuation properties of the spiked samples constant, decreasing amounts of an attenuation modifier [mercury (II) acetate] were added together with increasing amounts of the standard (lead nitrate). Linearity between fluorescence intensity and amount of lead was thus obtained, so the amount of lead in the sample could be evaluated by linear regression. The amount of modifier needed could be calculated from a simple expression. The method was validated by comparison with the results obtained by applying atomic-absorption spectrometry (AAS) to solutions made by leaching the fly-ash with strong acid. For 8 fly-ash samples, containing between 0.8 and 1.35% lead, the largest absolute difference between the two sets of results was 0.03%. Theoretical calculations based on a simplified version of the Sherman equation were performed to confirm the linearity of the modified standard-addition curves.

  • 11.
    Andersson, Örjan
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry, Analytical Chemistry.
    Two Modified 2,3-Diamino-naphthalenes for Spectro-fluorimetric Determination of Selenium in Biological Samples1995Licentiate thesis, monograph (Other academic)
  • 12.
    Bergens, Arne
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry, Analytical Chemistry.
    Determination of Aromatic Amines and Nitro Compounds by Voltammetry and Amperometric Detection in Liquid Chromatography1991Licentiate thesis, monograph (Other academic)
  • 13.
    Berglöf, Tomas
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry, Analytical Chemistry.
    Supercritical Fluid Extraction (SFE) in Environmental Analysis1996Licentiate thesis, monograph (Other academic)
  • 14.
    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
    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
    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
    Show others...
    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
    Show others...
    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
    Show others...
    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
  • 15.
    Bergström, Sara K.
    et al.
    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.
    Lavén, Martin
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry, Analytical Chemistry.
    Velikyan, Irina
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry, Organic Chemistry.
    Långström, Bengt
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry, Organic Chemistry.
    Markides, Karin E.
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry, Analytical Chemistry.
    Polyamine deactivation of integrated poly(dimethylsiloxane) structures investigated by radionuclide imaging and capillary electrophoresis experiments2005In: Analytical Chemistry, ISSN 0003-2700, E-ISSN 1520-6882, Vol. 77, no 3, p. 938-942Article in journal (Refereed)
    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.

  • 16.
    Bergström, Sara K
    et al.
    Uppsala University, Teknisk-naturvetenskapliga vetenskapsområdet, Chemistry, Department of Chemistry, Analytical Chemistry.
    Goiny, Michel
    Danielsson, Rolf
    Ungerstedt, Urban
    Andersson, Marit
    Markides, Karin E
    Screening of microdialysates using on-line desalting and mass spectrometric detectionIn: J. Chromatogr. AArticle in journal (Refereed)
  • 17.
    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.

  • 18.
    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.

  • 19.
    Bergström, Sara K
    et al.
    Uppsala University, Teknisk-naturvetenskapliga vetenskapsområdet, Chemistry, Department of Chemistry, Analytical Chemistry.
    Samskog, Jenny
    Markides, Karin 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., ISSN 0003-2700, Vol. 75, no 20, p. 5461-5467Article in journal (Refereed)
  • 20.
    Bhaskaran, Nimesh
    et al.
    Karolinska University Hospital.
    Iwahana, Hiroyuki
    Karolinska University Hospital.
    Bergquist, Jonas
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry, Analytical Chemistry.
    Hellman, Ulf
    Uppsala University, Disciplinary Domain of Medicine and Pharmacy, Medicinska och farmaceutiska vetenskapsområdet, centrumbildningar mm, Ludwig Institute for Cancer Research.
    Souchelnytskyi, Serhiy
    Karolinska University Hospital.
    Novel post-translational modifications of Smad2 identified by mass spectrometry2008In: Central European Journal of Biology, ISSN 1895-104X, E-ISSN 1644-3632, Vol. 3, no 4, p. 359-370Article in journal (Refereed)
    Abstract [en]

    Smad2 is a crucial component of transforming growth factor-b (TGFb) signaling, and is involved in the regulation of cell proliferation,death and differentiation. Phosphorylation, ubiquitylation and acetylation of Smad2 have been found to regulate its activity. We usedmass spectrometry to search for novel post-translational modifications (PTMs) of Smad2. Peptide mass fingerprinting (PMF) indicatedthat Smad2 can be acetylated, methylated, citrullinated, phosphorylated and palmitoylated. Sequencing of selected peptides validatedmethylation at Gly122 and hydroxylation at Trp18 of Smad2. We also observed a novel, so far unidentified modification at Tyr128 andTyr151. Our observations open for further exploration of biological importance of the detected PTMs.

  • 21. Bylund, Dan
    et al.
    Samskog, Jenny
    Uppsala University, Teknisk-naturvetenskapliga vetenskapsområdet, Chemistry, Department of Chemistry, Analytical Chemistry.
    Jacobsson, Sven P
    Markides, Karin E
    Classification of lactate dehydrogenase of different origin by liquid chromatography-mass spectrometry and multivariate analysis2003In: J Am Soc Mass Spectrom, Vol. 14, no 2, p. 236-240Article in journal (Refereed)
  • 22.
    Bäckström, Daniel
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry, Analytical Chemistry.
    Allard, Erik
    Danielsson, Rolf
    Sjöberg, Per
    Bergquist, Jonas
    Comparing CE-MS fingerprints of urine samples, obtained after intake of coffee, tea or waterManuscript (Other academic)
  • 23.
    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.

  • 24.
    Bökman, C Fredrik
    et al.
    Clinical Chemistry Laboratory, Falun Central Hospital.
    Bylund, Dan
    Department of Natural Sciences, Mid Sweden University.
    Markides, Karin E
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry, Analytical Chemistry.
    Sjöberg, Per J. R.
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry, Analytical Chemistry.
    Relating chromatographic retention and electrophoretic mobility to the ion distribution within electrosprayed droplets.2006In: Journal of the American Society for Mass Spectrometry, ISSN 1044-0305, E-ISSN 1879-1123, Vol. 17, no 3, p. 318-24Article in journal (Refereed)
    Abstract [en]

    Ions that are observed in a mass spectrum obtained with electrospray mass spectrometry can be assumed to originate preferentially from ions that have a high distribution to the surface of the charged droplets. In this study, a relation between chromatographic retention and electrophoretic mobility to the ion distribution (derived from measured signal intensities in mass spectra and electrospray current) within electrosprayed droplets for a series of tetraalkylammonium ions, ranging from tetramethyl to tetrapentyl, is presented. Chromatographic retention in a reversed-phase system was taken as a measure of the analyte's surface activity, which was found to have a large influence on the ion distribution within electrosprayed droplets. In addition, different transport mechanisms such as electrophoretic migration and diffusion can influence the surface partitioning coefficient. The viscosity of the solvent system is affected by the methanol content and will influence both diffusion and ion mobility. However, as diffusion and ion mobility are proportional to each other, we have, in this study, chosen to focus on the ion mobility parameter. It was found that the influence of ion mobility relative to surface activity on the droplet surface partitioning of analyte ions decreases with increasing methanol content. This effect is most probably coupled to the decrease in droplet size caused by the decreased surface tension at increasing methanol content. The same observation was made upon increasing the ionic strength of the solvent system, which is also known to give rise to a decreased initial droplet size. The observed effect of ionic strength on the droplet surface partitioning of analyte ions could also be explained by the fact that at higher ionic strength, a larger number of ions are initially closer to the droplet surface and, thus, the contribution of ionic transport from the bulk liquid to the liquid/air surface interface (jet and droplet surface), attributable to migration or diffusion will decrease.

  • 25.
    Carlsson, Annika
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry, Analytical Chemistry.
    Spectroscopy and Pattern Recognition as Alternative Methods to Biological Assays1995Licentiate thesis, monograph (Other academic)
  • 26.
    Dahlin, Andreas P.
    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.
    Andrén, Per E.
    Uppsala University, Disciplinary Domain of Medicine and Pharmacy, Faculty of Pharmacy, Department of Pharmaceutical Biosciences, MMS, Medical Mass Spectrometry.
    Markides, Karin E.
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry, Analytical Chemistry.
    Bergquist, Jonas
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry, Analytical Chemistry.
    Poly(dimethylsiloxane)-Based Microchip for Two-Dimensional Solid-Phase Extraction-Capillary Electrophoresis with an Integrated Electrospray Emitter Tip2005In: Analytical Chemistry, ISSN 0003-2700, E-ISSN 1520-6882, Vol. 77, no 16, p. 5356-5363Article in journal (Refereed)
    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.

  • 27.
    Danielsson, Rolf
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry, Analytical Chemistry.
    Bäckström, Daniel
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry, Analytical Chemistry.
    Ullsten, Sara
    Rapid multivariate analysis of LC/GC/CE data (single or multiple channel detection) without prior peak alignment2006In: Chemometrics and Intelligent Laboratory Systems, ISSN 0169-7439, E-ISSN 1873-3239, Vol. 84, no 1-2, p. 33-39Article in journal (Refereed)
    Abstract [en]

    One- or two-dimensional data obtained with LC/GC/CE and single or multiple channel detection (MS, UV/VIS) are often used as 'fingerprints' in order to characterize complex samples. The relation between samples is then explored by multivariate data analysis (PCA, hierarchical clustering), but inevitable more or less random variation in separation conditions obstructs the analysis. Several methods for peak alignment have been developed, with more or less increase of time and efforts for computations. In this work another approach is presented, based on a correlation measure less sensitive for variations in retention/migration time. The merits of the method as a fast initial data exploration tool are demonstrated for a case study of urine profiling with CE/MS.

  • 28.
    Drevin, Ingrid
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry, Analytical Chemistry.
    Determination of Ligand Concentration in Liquid Chromatography Media for Protein Purification1994Licentiate thesis, monograph (Other academic)
  • 29.
    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)
  • 30.
    Ericzon, Christina
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry, Analytical Chemistry.
    Determination of Lead and Selenium and Speciation of Selenium in Different End Products from a Garbage Incinerator1989Licentiate thesis, monograph (Other academic)
  • 31.
    Eriksson, Alf
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry, Analytical Chemistry.
    Carbon Electrodes for Analysis of Organic Compounds with some Applications1992Licentiate thesis, monograph (Other academic)
  • 32. Forngren, Benita H
    et al.
    Samskog, Jenny
    Uppsala University, Teknisk-naturvetenskapliga vetenskapsområdet, Chemistry, Department of Chemistry, Analytical Chemistry.
    Gustavsson, Sven Åke
    Tyrefors, Niklas
    Markides, Karin E
    Långström, Bengt
    Reversed-phase ion-pair chromatography coupled to electrospray ionisation mass spectrometry by on-line removal of the counter-ions1999In: J Chromatogr A, Vol. 854, no 1-2, p. 155-162Article in journal (Refereed)
  • 33.
    Forsgard, Niklas
    et al.
    Uppsala University, Teknisk-naturvetenskapliga vetenskapsområdet, Chemistry, Department of Chemistry, Analytical Chemistry.
    Nilsson, Eva
    Andersson, Marit
    Pettersson, Jean
    Investigation of matrix effects in boron determination using organic solvents as modifiers for liquid chromatography coupled to ICP-MS2006In: Journal of Analytical Atomic Spectrometry, ISSN 0267-9477, Vol. 21, no 3, p. 305 - 310Article in journal (Refereed)
  • 34. Forsgard, Niklas
    et al.
    Nilsson, Eva M
    Uppsala University, Teknisk-naturvetenskapliga vetenskapsområdet, Chemistry, Department of Chemistry, Analytical Chemistry.
    Andersson, Marit
    Markides, Karin E
    Pettersson, Jean
    Matrix effects of organic solvents in the determination of boron containing compounds by ICP-MSManuscript (Other academic)
  • 35. Gustavsson, Sven Åke
    et al.
    Samskog, Jenny
    Uppsala University, Teknisk-naturvetenskapliga vetenskapsområdet, Chemistry, Department of Chemistry, Analytical Chemistry.
    Markides, Karin E
    Långström, Bengt
    Studies of signal suppression in liquid chromatography–electrospray ionization mass spectrometry using volatile ion-pairing reagents2001In: J Chromatogr A, Vol. 937, no 1-2, p. 41-47Article in journal (Refereed)
  • 36. Hagman, Charlotte
    et al.
    Ramström, Margareta
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry, Analytical Chemistry.
    Håkansson, Per
    Bergquist, Jonas
    Quantitative Analysis of Tryptic Protein Mixtures Using Electrospray Ionization Fourier Transform Ion Cyclotron Mass Spectrometry2004In: Journal of Proteome Research, ISSN 1535-3893, Vol. 3, no 3, p. 587-594Article in journal (Refereed)
  • 37.
    Hellberg, Ulf
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry, Analytical Chemistry.
    Kemisk och Funktionell Karaktärisering av Vätske-kromatografimedia för Proteinrening1995Licentiate thesis, monograph (Other academic)
  • 38.
    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
    Show others...
    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
    Show others...
    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
    Show others...
    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
  • 39.
    Isaac, Giorgis
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry, Analytical Chemistry.
    Bylund, Dan
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry, Analytical Chemistry.
    Månsson, Jan-Eric
    Institute of Clinical Neuroscience, Sahlgrenska University Hospital, Göteborg University, Sweden.
    Markides, Karin
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Physical and Analytical Chemistry, Analytical Chemistry.
    Bergquist, Jonas
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Physical and Analytical Chemistry, Analytical Chemistry.
    Analysis of phosphatidylcholine and sphingomyelin molecular species from brain extracts using capillary liquid chromatography electrospray ionization mass spectrometry2003In: Journal of Neuroscience Methods, ISSN 0165-0270, E-ISSN 1872-678X, Vol. 128, no 1-2, p. 111-119Article in journal (Refereed)
    Abstract [en]

    One feature of complex lipids is that many subtypes of these molecules exist as a diverse mixture in a biological sample. Qualitative and quantitative analysis of these closely related molecules require sensitive and specific analytical methods to detect intact phospholipids (PL) and sphingomyelin (SM) species and to differentiate between them. Conventional analytical methods require laborious procedures including separation by column, argentation thin-layer chromatography or liquid chromatography (LC) after pre- or post-column derivatization. In the present work, a method based on reversed phase capillary LC coupled on-line to electrospray ionization mass spectrometry (LC/ESI/MS) has been developed to gather tools for lipidomic studies, i.e. the profiling of complex mixtures of lipids in small amounts of various cells and tissues. The LC/MS system used consisted of an LC pump in an isocratic elution, a reversed phase capillary column and a single quadrupole mass spectrometer operated in the positive ion mode. A successful separation of phosphatidylcholine (PC) and SM molecular species was obtained with a minimum detectable quantity (MDQ) in the low fmol range injected on column. The method was applied to human brain extracts. Furthermore, the extraction efficiencies of the traditional Folch method and pressurized fluid extraction (PFE) were compared using the human brain. It was found that the intensity of the PC and SM molecular species extracted by PFE is two times that of Folch.

  • 40.
    Isaac, Giorgis
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry, Analytical Chemistry.
    Bylund, Dan
    Månsson, Jan-Eric
    Markides, Karin E.
    Bergquist, Jonas
    Analysis of Phosphatidylcholine and Sphingomyelin Molecular Species From Brain Extracts Using Capillary Liquid Chromatography Electrospray Ionization Mass Spectrometry2003In: Journal of Neuroscience Methods, ISSN 0165-0270, Vol. 128, no 1-2, p. 111-119Article in journal (Refereed)
  • 41.
    Isaac, Giorgis
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry, Analytical Chemistry.
    Fredriksson, Anders
    Danielsson, Rolf
    Eriksson, Per
    Bergquist, Jonas
    Brain Lipid Composition in Postnatal Iron-Induced Motor Behavior Alterations Following Chronic Neuroleptic Administration in MiceIn: Neuroscience LettersArticle in journal (Refereed)
  • 42.
    Isaac, Giorgis
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry, Analytical Chemistry.
    Månsson, Jan-Eric
    Gieselmann, Volkmar
    Hansson, Elisabeth
    Pernber, Zarah
    Bergquist, Jonas
    Characterization of Brain Sulfatide Molecular Species in Arylsulfatase A Deficient Mice Using Electrospray Ionization Tandem Mass SpectrometryManuscript (Other academic)
  • 43.
    Isaac, Giorgis
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry, Analytical Chemistry.
    Waldebäck, Monica
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry, Analytical Chemistry.
    Eriksson, Ulla
    Odham, Göran
    Markides, Karin E.
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry, Analytical Chemistry.
    Total Lipid Extraction of Homogenized and Intact Lean Fish Muscles Using Pressurized Fluid Extraction and Batch Extraction Technique2005In: Journal of Agricultural and Food Chemistry, ISSN 0021-8561, E-ISSN 1520-5118, Vol. 53, no 14, p. 5506-5512Article in journal (Refereed)
    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.

  • 44. Jansson, Christer
    et al.
    Pihlström, Tuija
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry, Analytical Chemistry.
    Österdahl, Bengt-Göran
    Markides, Karin E
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry, Analytical Chemistry.
    A new multi-residue method for analysis of pesticide residues in fruit and vegetables using liquid chromatography with tandem mass spectrometric detection2004In: Journal of Chromatography A, ISSN 0021-9673, E-ISSN 1873-3778, Vol. 1023, no 1, p. 93-104Article in journal (Refereed)
    Abstract [en]

    A new multi-residue method for determination of pesticide residues in a wide variety of fruit and vegetables, using the National Food Administration (NFA) ethyl acetate extraction and determination by means of LC-MS/MS, is presented. The method includes pesticides normally detected by LC-UV or LC-fluorescence such as benzimidazoles, carbamates, N-methylcarbamates and organophosphorus compounds with an oxidisable sulphide group as well. After extraction with ethyl acetate, the extract is concentrated and an aliquot of the extract is evaporated to dryness and redissolved in methanol before injection on LC-MS/MS. The method has been validated for 57 different pesticides and metabolites. Representative species from different commodity groups were chosen as matrices in order to study the influence from different matrices on recoveries. The fortification levels studied were 0.01-0.5 mg kg(-1). Matrix effects were tested for all matrices by means of standard addition to blank extracts. The matrix effect, expressed as signal in solvent compared to signal in matrix, was in general found to be small. The obtained recoveries are, with a few exceptions, in the range 70-100%. The proposed method is quick and straightforward and no additional clean-up steps are needed. The method can be used for the analysis of all 57 pesticides in one single determination step at 0.01 mg kg(-1).

  • 45.
    Jastrebova, Jalena
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry, Analytical Chemistry.
    Determination of Mefloquine Enantiomers and their Main Metabolite in Biological Fluids1996Licentiate thesis, monograph (Other academic)
  • 46.
    Johannesson, Nina
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry, Analytical Chemistry.
    Wetterhall, Magnus
    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.
    Bergquist, Jonas
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry, Analytical Chemistry.
    Monomer surface modifications for rapid peptide analysis by capillary electrphoresis and capillary electrochromatography coupled to electrospray ionization mass spectrometry2004In: Electrophoresis, ISSN 0173-0835, E-ISSN 1522-2683, Vol. 25, no 6, p. 809-816Article in journal (Refereed)
    Abstract [en]

    In this study, positively charged alkylaminosilyl monomers were used to modify the inner surface of fused silica capillaries, which subsequently were employed in capillary electrophoresis (CE) and capillary electrochromatography (CEC). The obtained surfaces yield a reversed electroosmotic flow (EOF) and have varying carbon chain lengths, that interact with the analytes and give chromatographic retention. The coating procedure is very simple and fast. The performance of the modified capillaries was evaluated regarding pH influence on EOF and chromatographic interactions. The experiments were conducted with UV and mass spectrometry (MS) and applied to the separation of various neuropeptides. The derivatized surfaces showed a linear (R2 ∼0.99) pH dependence with isoelectric points (pI) at 8.6–8.8. Rapid separations of peptide standards and a protein digest with efficiencies as high as 5×105 plates/m were performed.

  • 47. Johansson, Olof
    et al.
    Wolpher, Henriette
    Borgström, Magnus
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Physical Chemistry.
    Hammarström, L.eif
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Physical Chemistry.
    Bergquist, Jonas
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry, Analytical Chemistry.
    Sun, Licheng
    Åkermark, Björn
    Intramolecular charge separation in a hydrogen bonded tyrosine-ruthenium(II)-naphthalene diimide triad2004In: Chemical Communications, ISSN 1359-7345, E-ISSN 1364-548X, no 2, p. 194-195Article in journal (Refereed)
    Abstract [en]

    Long-lived charge-separated states in the ns to [micro sign]s range were observed upon laser flash excitation of a donor-chromophore-acceptor triad based on tris(bipyridine) ruthenium(ii) as photo-sensitizer, naphthalene diimide as acceptor, and a hydrogen bonded phenol as donor.

  • 48.
    Koivisto, P.
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry, Analytical Chemistry.
    Törnkvist, Anna
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry, Analytical Chemistry.
    Heldin, E.
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry, Analytical Chemistry.
    Markides, K. E.
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry, Analytical Chemistry.
    Separation of L-DOPA and four metabolites in plasma using a porous graphitic carbon column in capillary liquid chromatography2002In: Chromatographia, ISSN 0009-5893, E-ISSN 1612-1112, Vol. 55, no 1-2, p. 39-42Article in journal (Refereed)
    Abstract [en]

    Porous graphitic carbon has been successfully used for the separation of L-DOPA and four metabolites (dopamine, 3,4-dihydroxy-phenyl-acetic acid, homovanillic acid and 3-O-methyl-L-DOPA) and with a volatile mobile phase of relatively high percentage organic modifier (methanol-ammonium formate pH 2.9, 60∶40, v/v). The substances were analysed in plasma. Ultrafiltration was used to remove the proteins from the sample and a coupled column system to enrich and perform on-line sample clean up. Both precolumn and separation column of i. d. 0.2 mm were packed with porous graphitic carbon.

  • 49.
    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%.

  • 50. Kollander, Barbro
    et al.
    Forsgard, Niklas
    Uppsala University, Teknisk-naturvetenskapliga vetenskapsområdet, Chemistry, Department of Chemistry, Analytical Chemistry.
    Andersson, Marit
    Pettersson, Jean
    Analysis of non-dissolved organic materials by ICP-AES and ICP-TOF-MSManuscript (Other academic)
123 1 - 50 of 131
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