uu.seUppsala University Publications
Change search
Refine search result
1 - 30 of 30
CiteExportLink to result list
Permanent link
Cite
Citation style
  • apa
  • ieee
  • modern-language-association
  • vancouver
  • Other style
More styles
Language
  • de-DE
  • en-GB
  • en-US
  • fi-FI
  • nn-NO
  • nn-NB
  • sv-SE
  • Other locale
More languages
Output format
  • html
  • text
  • asciidoc
  • rtf
Rows per page
  • 5
  • 10
  • 20
  • 50
  • 100
  • 250
Sort
  • Standard (Relevance)
  • Author A-Ö
  • Author Ö-A
  • Title A-Ö
  • Title Ö-A
  • Publication type A-Ö
  • Publication type Ö-A
  • Issued (Oldest first)
  • Issued (Newest first)
  • Created (Oldest first)
  • Created (Newest first)
  • Last updated (Oldest first)
  • Last updated (Newest first)
  • Disputation date (earliest first)
  • Disputation date (latest first)
  • Standard (Relevance)
  • Author A-Ö
  • Author Ö-A
  • Title A-Ö
  • Title Ö-A
  • Publication type A-Ö
  • Publication type Ö-A
  • Issued (Oldest first)
  • Issued (Newest first)
  • Created (Oldest first)
  • Created (Newest first)
  • Last updated (Oldest first)
  • Last updated (Newest first)
  • Disputation date (earliest first)
  • Disputation date (latest first)
Select
The maximal number of hits you can export is 250. When you want to export more records please use the 'Create feeds' function.
  • 1.
    Bökman, C.Fredrik
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry. Analytisk kemi.
    Zettersten, Camilla
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry. Analytisk kemi.
    Sjöberg, Per J.R.
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry. Analytisk kemi.
    Nyholm, Leif
    A Setup for the Coupling of a Thin-Layer Electrochemical Flow Cell to Electrospray Mass Spectrometry2004In: Analytical Chemistry, Vol. 76, no 7, p. 2017-2024Article in journal (Refereed)
    Abstract [en]

    A novel setup for the coupling of commercially available thin-layer cell to electrospray mass spectrometry (ESI-MS) which allows the elctrochemical reactions at the counter electrode to be straightforwardly separated from the flow into the mass spectrometer has been developed. In this way interferences from reaction products formed at the counter electrode can be minimized. This reduces the risk of changes in the mass spectra as a result of electrochemical reactions in the solution. The described setup also enables the working electrode to be positioned close to the electrospray (ESI) emitter without the need for a grounding point or a long transfer line between the electrochemical cell and the electrospray emitter. By decoupling the electrochemical reactions in the flow cell and those in the electrospray emitter, improved facilities for studies of electrochemical reactions are obtained through a better control of the potential of the working electrode. The setup has been used to study the oxidation of a drug (Olsalazine), which previously has been found to involve chemical follow-up reactions. It is also demonstrated that uncharged thiols can be detected in ESI-MS after spontaneous adsorption on a gold working electrode, followed by oxidative desorption to yield sulfinates or sulfonates. This adsorption and potential-controlled desorption has been used for the preconcentration of micromolar concentrations of 1-hexanethiol as well as for desalting of solutions containing micromolar concentrations of thiols. The results indicate that the present on-line coupling of an electrochemical cell to ESI-MS provides promising possibilities for sample preconcentration, matrix exchange (including desalting), and ionization of neutral compounds, such as thiols.

  • 2.
    Eilers, Gerriet
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry.
    Zettersten, Camilla
    Nyholm, Leif
    Hammarström, Leif
    Lomoth, Reiner
    Ligand exchange upon oxidation of a dinuclear Mn complex - Detection of structural changes by FT-IR spectroscopy and ESI-MS.2005In: Dalton Transactions, ISSN 1477-9226, E-ISSN 1477-9234, no 6, p. 1033-1041Article in journal (Refereed)
  • 3.
    Klett, Oliver
    et al.
    Uppsala University, Teknisk-naturvetenskapliga vetenskapsområdet, Chemistry, Department of Chemistry.
    Björefors, Fredrik
    Nyholm, Leif
    Elimination of High Voltage Field Effects in End Column Electrochemical Detection in Capillary Electrophoresis by use of On-Chip Microband Electrodes2001In: Analytical Chemistry, Vol. 73, no 8, p. 1909-1915Article in journal (Refereed)
  • 4.
    Klett, Oliver
    et al.
    Uppsala University, Teknisk-naturvetenskapliga vetenskapsområdet, Chemistry, Department of Chemistry.
    Nischang, Ivo
    Nyholm, Leif
    III. Deviceless Decoupled Electrochemical Detection of Catecholamines in Capillary Electrophoresis using Gold Microband Array Electrodes2002In: Electrophoresis, Vol. 23, p. 3678-3682Article in journal (Refereed)
  • 5.
    Klett, Oliver
    et al.
    Uppsala University, Teknisk-naturvetenskapliga vetenskapsområdet, Chemistry, Department of Chemistry.
    Nyholm, Leif
    Separation High Voltage-Field Driven On-Chip Amperometric Detection in Capillary Electrophoresis2003In: Analytical Chemistry, Vol. 74, no 6, p. 1245-1250Article in journal (Refereed)
  • 6.
    Liljegren, G
    et al.
    Uppsala University, Teknisk-naturvetenskapliga vetenskapsområdet, Chemistry, Department of Chemistry. Department of Materials Chemistry, Inorganic Chemistry.
    Nyholm, Leif
    Department of Materials Chemistry, Inorganic Chemistry. oorganisk kemi.
    Electrochemically Controlled Solid Phase Microextraction and Preconcentration using Polypyrrole Coated Microarray Electrodes in a Flow System2003In: presented at the 26th International Symposium on Capillary Chromatography & Electrophoresis, Las Vegas, USA, May 18-22, 2003, 2003Conference paper (Refereed)
  • 7.
    Liljegren, Gustav
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry.
    Dahlin, Andreas P.
    Zettersten, Camilla
    Bergquist, Jonas
    Nyholm, Leif
    On-line coupling of a microelectrode array equipped poly(dimethylsiloxane) microchip with an integrated graphite electrospray emitter to electrospray ionisation mass spectrometryManuscript (Other academic)
  • 8. Liljegren, Gustav
    et al.
    Dahlin, Andreas P.
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry.
    Zettersten, Camilla
    Bergquist, Jonas
    Nyholm, Leif
    On-line coupling of a microelectrode array equipped poly(dimethylsiloxane) microchip with an integrated graphite electrospray tip to electrospray mass spectrometryIn: Article in journal (Refereed)
  • 9.
    Liljegren, Gustav
    et al.
    Uppsala University, Teknisk-naturvetenskapliga vetenskapsområdet, Chemistry, Department of Chemistry. Department of Materials Chemistry, Inorganic Chemistry. Analytisk kemi.
    Dahlin, Andreas
    Uppsala University, Teknisk-naturvetenskapliga vetenskapsområdet, Chemistry, Department of Chemistry. Department of Materials Chemistry, Inorganic Chemistry. Analytisk kemi.
    Zettersten, Camilla
    Uppsala University, Teknisk-naturvetenskapliga vetenskapsområdet, Chemistry, Department of Chemistry. Department of Materials Chemistry, Inorganic Chemistry. Analytisk kemi.
    Bergquist, Jonas
    Uppsala University, Teknisk-naturvetenskapliga vetenskapsområdet, Chemistry, Department of Chemistry. Department of Materials Chemistry, Inorganic Chemistry. Analytisk kemi.
    Nyholm, Leif
    Department of Materials Chemistry, Inorganic Chemistry. Oorganisk kemi.
    On-line coupling of a microelectrode array equipped poly(dimethylsiloxane) microchip with an integrated graphite electrospray emitter for electrospray ionisation mass spectrometry2005In: Lab on a Chip, no 5, p. 1008-1016Article in journal (Refereed)
    Abstract [en]

    A novel method for the manufacturing of microchips for on-chip combinations of electrochemistry (EC) and sheathless electrospray ionisation mass spectrometry (ESI-MS) is described. The technique, which does not require access to clean-room facilities, is based on the incorporation of an array of gold microcoil electrodes into a poly(dimethylsiloxane) (PDMS) microflow channel equipped with an integrated graphite based sheathless ESI emitter. Electrochemical measurements, which were employed to determine the electroactive area of the electrodes and to test the microchips, show that the manufacturing process was reproducible and that the important interelectrode distance in the electrochemical cell could to be adequately controlled. The EC-ESI-MS device was evaluated based on the ESI-MS detection of the oxidation products of dopamine. The results demonstrate that the present on-chip approach enables full potentiostatic control of the electrochemical cell and the attainment of very short transfer times between the electrochemical cell and the electrospray emitter. The transfer times were 0.6 and 1.2 s for flow rates of 1.0 and 0.5 uL min-1, respectively, while the electrochemical conversion efficiency of the electrochemical cell was found to be 30% at a flow rate of 0.5 uL min-1. To decouple the electrochemical cell from the ESI-MS high voltage and to increase the user-friendliness, the on-line electrochemistry-ESI-MS experiments were performed using a wireless Bluetooth battery-powered instrument with the chip floating at the potential induced by the ESI high voltage. The described on-chip EC-ESI-MS device can be used for fundamental electrochemical investigations as well as for applications based on the use of electrochemically controlled sample pretreatment, preconcentration and ionisation steps prior to ESI-MS.

  • 10.
    Liljegren, Gustav
    et al.
    Uppsala University, Teknisk-naturvetenskapliga vetenskapsområdet, Chemistry, Department of Chemistry.
    Forsgard, Niklas
    Zettersten, Camilla
    Pettersson, Jean
    Svedberg, Malin
    Herranen, Merja
    Nyholm, Leif
    On-line electrochemically controlled solid-phase extraction coupled to electrospray and inductively coupled plasma mass spectrometryManuscript (Other academic)
  • 11. Liljegren, Gustav
    et al.
    Forsgard, Niklas
    Uppsala University, Teknisk-naturvetenskapliga vetenskapsområdet, Chemistry, Department of Chemistry, Analytical Chemistry.
    Zettersten, Camilla
    Pettersson, Jean
    Svedberg, Malin
    Herranen, Merja
    Nyholm, Leif
    On-line electrochemically controlled solid-phase extraction interfaced to electrospray and inductively coupled plasma mass spectrometry2005In: The Analyst, ISSN 0003-2654, Vol. 130, no 10, p. 1358-1368Article in journal (Refereed)
  • 12.
    Liljegren, Gustav
    et al.
    Uppsala University, Teknisk-naturvetenskapliga vetenskapsområdet, Chemistry, Department of Chemistry. Department of Materials Chemistry, Inorganic Chemistry. Analytisk kemi.
    Forsgard, Niklas
    Uppsala University, Teknisk-naturvetenskapliga vetenskapsområdet, Chemistry, Department of Chemistry. Department of Materials Chemistry, Inorganic Chemistry. Analytisk kemi.
    Zettersten, Camilla
    Uppsala University, Teknisk-naturvetenskapliga vetenskapsområdet, Chemistry, Department of Chemistry. Department of Materials Chemistry, Inorganic Chemistry. Analytisk kemi.
    Pettersson, Jean
    Uppsala University, Teknisk-naturvetenskapliga vetenskapsområdet, Chemistry, Department of Chemistry. Department of Materials Chemistry, Inorganic Chemistry. Analytisk kemi.
    Svedberg, Malin
    Herranen, Merja
    Department of Materials Chemistry, Inorganic Chemistry. Oorganisk kemi.
    Nyholm, Leif
    Department of Materials Chemistry, Inorganic Chemistry. Oorganisk kemi.
    On-line electrochemically controlled solid-phase extraction interfaced to electrospray and inductively coupled plasma mass spectrometry2005In: The Analyst, no 130, p. 1358-1368Article in journal (Refereed)
    Abstract [en]

    Electrochemically controlled solid-phase extractions of anions were interfaced on-line to electrospray mass spectrometry (ESI-MS) and inductively coupled plasma mass spectrometry (ICP-MS), using polypyrrole coated electrodes and a thin-layer electrochemical (EC) flow cell. The results indicate that electrochemically controlled solid-phase extraction (EC-SPE) can be used as a versatile potential controlled sample preparation technique for a range of anions and that the properties of the polypyrrole coatings can be modified by altering the electrodeposition conditions. In the present study, the influence of interfering anions (i.e., fluoride and sulfate), and the anion used during the electropolymerisation, on the bromide extraction recovery was investigated for EC-SPE interfaced to ICP-MS. The results of these experiments show that the interference due to the presence of similar concentrations of sulfate can be reduced when using a polypyrrole coating electropolymerised in the presence of bromide ions. Scanning electron microscopy (SEM) and atomic force microscopy (AFM) measurements were also used to study the morphology of the coatings, as well as the variations in the film thickness within the coatings. The effect of different desorption techniques on the bromide preconcentration factor in the ICP-MS on-line flow system was also examined. Stopped-flow desorption was found to give rise to significantly increased preconcentration factors in comparison with desorptions in flowing solutions. While the desorption efficiency depends on the type of desorption electrolyte (the electrolyte in which the desorption takes place), due to the competing influx of cations, the influence of the pH on the switching charge of the polypyrrole coating was found to be small, at constant ionic strength. To study the applicability of the EC-SPE technique with respect to real samples, investigations were also made with tap water samples spiked with different bromide concentrations. The results of these experiments, which were carried out using a modified thin-layer EC flow cell allowing in situ polymerisation of polypyrrole yielding a polymer plug covering the cross section of the channel, demonstrate that 3 uM concentrations of bromide could be detected in the tap water sample. This demonstrates that the extraction technique allows extractions of low concentrations of ions in the presence of significantly higher concentrations of other similar ions. The fact that the extraction and desorption steps are electrochemically controlled makes EC-SPE particularly well suited for inclusion in miniaturised lab-on-a-chip systems.

  • 13.
    Liljegren, Gustav
    et al.
    Uppsala University, Teknisk-naturvetenskapliga vetenskapsområdet, Chemistry, Department of Chemistry.
    Nyholm, Leif
    Electrochemically controlled solid-phase microextraction and preconcentration using polypyrrole coated microarray electrodes in a flow system2003In: The Analyst, ISSN 0003-2654, Vol. 128, no 3, p. 232-236Article in journal (Refereed)
  • 14.
    Liljegren, Gustav
    et al.
    Uppsala University, Teknisk-naturvetenskapliga vetenskapsområdet, Chemistry, Department of Chemistry.
    Pettersson, Jean
    Markides, Karin E.
    Nyholm, Leif
    Electrochemical solid-phase microextraction of anions and cations using polypyrrole coatings and an integrated three-electrode device2002In: The Analyst, ISSN 0003-2654, Vol. 127, no 5, p. 591-597Article in journal (Refereed)
  • 15.
    Nilsson, Stefan
    et al.
    Uppsala University, Teknisk-naturvetenskapliga vetenskapsområdet, Chemistry, Department of Chemistry.
    Klett, Oliver
    Svedberg, Malin
    Amirkhani, Ardeshir
    Nyholm, Leif
    Gold-coated fused-silica sheathless electrospray emitters based on vapor-deposited titanium adhesion layers2003In: Rapid Communications in Mass Spectrometry, ISSN 0951-4198, Vol. 17, no 14, p. 1535-1540Article in journal (Refereed)
  • 16. Nilsson, Stefan
    et al.
    Klett, Oliver
    Svedberg, Malin
    Amirkhani, Ardeshir
    Uppsala University, Teknisk-naturvetenskapliga vetenskapsområdet, Chemistry, Department of Chemistry, Analytical Chemistry.
    Nyholm, Leif
    Gold-coated fused-silica sheathless electrospray emitters based on vapor-deposited titanium adhesion layers2003In: Rapid Communication Mass Spectrometry, Vol. 17, no 14, p. 1535-1540Article in journal (Refereed)
  • 17. Nilsson, Stefan
    et al.
    Klett, Oliver
    Uppsala University, Teknisk-naturvetenskapliga vetenskapsområdet, Chemistry, Department of Chemistry.
    Svedberg, Malin
    Nyholm, Leif
    Titanium/Gold Coated Fused Silica Sheathless Electrospray Emitters2003In: Rapid communications in Mass Spectrometry, Vol. 17, no 14, p. 1535-1540Article in journal (Refereed)
  • 18.
    Nilsson, Stefan
    et al.
    Uppsala University, Teknisk-naturvetenskapliga vetenskapsområdet, Chemistry, Department of Chemistry.
    Svedberg, Malin
    Pettersson, Jean
    Björefors, Fredrik
    Markides, Karin
    Nyholm, Leif
    Evaluations of the stability of sheathless electrospray ionization mass spectrometry emitters using electrochemical techniques2001In: Analytical Chemistry, ISSN 0003-2700, Vol. 73, no 19, p. 4607-4616Article in journal (Refereed)
  • 19.
    Nilsson, Stefan
    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.
    Bergquist, Jonas
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry, Analytical Chemistry.
    Nyholm, Leif
    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.
    A simple and robust conductive graphite coating for sheathless electrospray emitters used in capillary electrophoresis/mass spectrometry2001In: Rapid Communications in Mass Spectrometry, ISSN 0951-4198, E-ISSN 1097-0231, Vol. 15, no 21, p. 1997-2000Article in journal (Refereed)
    Abstract [en]

    A graphite-polyimide mixture was used as a conductive coating for sheathless electrospray emitters. The coating procedure described is simple and inexpensive compared to previously described methods. An investigation of the stability of the conductive coating carried out by electrochemical methods revealed good performances during oxidative stress. In addition, no decrease in emitter performance was seen during continuous electrospray in the positive electrospray mode for two weeks. Fast capillary electrophoresis with attomole sensitivity demonstrated the excellent performance of the described sheathless interface when used in conjunction with an orthogonal time-of-flight mass spectrometer. The overall simplicity, stability and low cost of this type of sheathless emitter make the described approach highly suitable for any on-column coupling of low flow rate separation techniques to a mass spectrometer.

  • 20.
    Nyholm, Leif
    et al.
    Uppsala University, Teknisk-naturvetenskapliga vetenskapsområdet, Chemistry, Department of Materials Chemistry. oorganisk kemi.
    Zettersten, Camilla
    Department of Chemistry. analytisk kemi.
    Bökman, Fredrik
    Department of Chemistry. analytisk kemi.
    Sjöberg, Per
    Department of Chemistry. analytisk kemi.
    Nilsson, S
    Department of Chemistry. analytisk kemi.
    On the coupling of Electrochemical Cells to Electrospray Ionisation Mass Spectrometry2004In: ESEAC 10th International Conference on Electroanalysis of the European Society for ElectroAnalytical Chemistry, Galway 6-10 June 2004, 2004Conference paper (Other scientific)
  • 21.
    Pettersson Dahlin, Andreas
    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.
    Liljegren, Gustav
    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
    Uppsala University, Disciplinary Domain of Medicine and Pharmacy, Faculty of Pharmacy, Department of Pharmaceutical Biosciences.
    Nyholm, Leif
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Materials Chemistry, Materials 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.
    Capillary electrophoresis coupled to mass spectrometry from a polymer modified poly(dimethylsiloxane) microchip with an integrated graphite electrospray tip2005In: The Analyst, ISSN 0003-2654, E-ISSN 1364-5528, Vol. 130, no 2, p. 193-199Article in journal (Refereed)
    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.

  • 22. Richard, Åse
    et al.
    Klett, Oliver
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry.
    Strandman, Carola
    Bäcklund, Ylva
    Nyholm, Leif
    Design of a Chip Based Microanalytical Fluidic System Based on Electrochemical Detection Using Redox Cycling1999In: MEMS-Proceedings of the ASME International Mechanical Engineering, Congress and Exposition, Vol. 1, no 1, p. 511-516Article in journal (Refereed)
  • 23. Svedberg, Malin
    et al.
    Pettersson, Andreas
    Nilsson, Stefan
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry.
    Bergquist, Jonas
    Nyholm, Leif
    Nikolajeff, Fredrik
    Markides, Karin
    Sheathless electrospray from polymer microchips2003In: Analytical Chemistry, ISSN 0003-2700, Vol. 75, no 15, p. 3934-3940Article in journal (Refereed)
  • 24.
    Svedberg, Malin
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry.
    Pettersson, Andreas
    Nilsson, Stefan
    Nyholm, Leif
    Nikolajeff, Fredrik
    Bergquist, Jonas
    Markides, Karin E.
    Sheathless electrospray from polymer microchips2003In: Analytical Chemistry, Vol. 75, no 15, p. 3934-3940Article in journal (Refereed)
  • 25.
    Thorslund, Sara
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences.
    Bergström, S
    Johanesson, N
    Pettersson, A
    Liljegren, G
    Magnusson, K
    Uppsala University, Disciplinary Domain of Medicine and Pharmacy, Faculty of Pharmacy, Department of Pharmaceutical Biosciences.
    Hallberg, M
    Uppsala University, Disciplinary Domain of Medicine and Pharmacy, Faculty of Pharmacy, Department of Pharmaceutical Biosciences.
    Klett, Oliver
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences.
    Bergquist,, Jonas
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry, Analytical Chemistry.
    Nyholm, Leif
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Materials Chemistry.
    Markides, Karin
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Materials Chemistry, Inorganic Chemistry. Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Materials Science.
    Nyberg, F
    Uppsala University, Disciplinary Domain of Medicine and Pharmacy, Faculty of Pharmacy, Department of Pharmaceutical Biosciences. Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Materials Chemistry, Inorganic Chemistry. Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Materials Science.
    Nikolajeff, Fredrik
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences.
    Essential components in an integrated platform for on-site screening of anabolic androgenic steroids in biological samples2004In: Micro Total Analysis Systems 2004: Vol 1 / [ed] Laurell T; Nilsson J; Jensen K; Harrison DJ; Kutter JP, 2004Conference paper (Refereed)
    Abstract [en]

    In this abstract new results concerning the introduction of a biological sample into a mu TAS, the avoidance of unspecific absorbance in the mu TAS and the interfacing to off-chip detection (e.g. Mass spectrometry, MS) for verification are presented.

  • 26.
    Törnkvist, Anna
    et al.
    Uppsala University, Teknisk-naturvetenskapliga vetenskapsområdet, Chemistry, Department of Chemistry, Analytical Chemistry.
    Markides, Karin E.
    Nyholm, Leif
    Chromatographic behavior of oxidized porous graphitic carbon columnsManuscript (Other academic)
  • 27.
    Törnkvist, Anna
    et al.
    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.
    Amirkhani, Ardeshir
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry, Analytical Chemistry.
    Nyholm, Lena
    Nyholm, Leif
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry, Analytical Chemistry.
    Interference of the electrospray voltage on chromatographic separations using porous graphitic carbon columns2004In: Journal of Mass Spectrometry, ISSN 1076-5174, E-ISSN 1096-9888, Vol. 39, no 2, p. 216-222Article in journal (Refereed)
    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.

  • 28.
    Wetterhall, Magnus
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry.
    Klett, Oliver
    Markides, Karin E.
    Nyholm, Leif
    Bergquist, Jonas
    A comparison of the electrochemical stabilities of metal, polymer and graphite coated nanospray emitters2003In: The Analyst, ISSN 0003-2654, Vol. 128, no 6, p. 728-733Article in journal (Refereed)
  • 29. Wetterhall, Magnus
    et al.
    Klett, Oliver
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry.
    Nyholm, Leif
    Bergquist, Jonas
    A Comparison of the Electrochemical Stabilities of some Metal, Polymer and Carbon Coated Nanospray Emitters2003In: Analyst, Vol. 128, no 6, p. 728-733Article in journal (Refereed)
  • 30.
    Zettersten, Camilla
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry, Analytical Chemistry.
    Lomoth, Reiner
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Physical Chemistry.
    Hammarström, Leif
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Physical Chemistry.
    Sjöberg, Per
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry, Analytical Chemistry.
    Nyholm, Leif
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Materials Chemistry.
    The influence of the thin-layer flow cell design on the mass spectra when coupling electrochemistry to electrospray ionisation mass spectrometry2006In: Journal of Electroanalytical Chemistry, ISSN 0022-0728, E-ISSN 1873-2569, Vol. 590, no 1, p. 90-99Article in journal (Refereed)
    Abstract [en]

    The influence of the flow cell configuration on the mass spectra obtained when coupling an electrochemical thin-layer flow cell to electrospray mass spectrometry (ESI-MS) has been investigated. It is shown that interferences due to the electrochemical reaction on the counter electrode and/or the absence of 100% conversion efficiency can alter the mass spectra when conventional thin-layer flow cells are used in conjunction with ESI-MS. The effects, which affect the intensities and distribution of the peaks in the mass spectra, can result in the inability to detect products formed at the working electrode. Comparisons of mass spectra, generated after the electrochemical oxidation of a dinuclear Mn complex (where bpmp = 2,6-bis[bis(2-pyridylmethyl) amino]methyl-4-methylphenol) using two different thin-layer flow cells clearly show that the potential dependence and appearance of the mass spectra depend on the flow cell configuration used. The use of a modified thin-layer flow cell, in which the counter electrode had been separated from the working electrode, gave rise to significantly increased intensities for the oxidised MnIII,IV state of the complex. With the conventional unmodified cell, the corresponding complex was only seen for considerably higher oxidation potentials. The different results can be explained by the reduced risk of redox cycling and interferences due to species generated at the counter electrode with the modified cell. As interferences due to the counter electrode reactions likewise may be expected with many coulometric flow cells, the electrochemical cell design clearly needs to be considered when using electrochemistry coupled to ESI-MS to study electrochemical reactions.

1 - 30 of 30
CiteExportLink to result list
Permanent link
Cite
Citation style
  • apa
  • ieee
  • modern-language-association
  • vancouver
  • Other style
More styles
Language
  • de-DE
  • en-GB
  • en-US
  • fi-FI
  • nn-NO
  • nn-NB
  • sv-SE
  • Other locale
More languages
Output format
  • html
  • text
  • asciidoc
  • rtf