uu.seUppsala University Publications
Change search
CiteExportLink to record
Permanent link

Direct 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
On-column polymer-imbedded graphite inlet electrode for capillary electrophoresis coupled on-line with flow injection analysis in a poly(dimethylsiloxane) interface
Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry, Analytical Chemistry.
Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry, Analytical Chemistry.
Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Electronics.
Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry, Analytical Chemistry.
Show others and affiliations
2003 (English)In: Electrophoresis, ISSN 0173-0835, E-ISSN 1522-2683, Vol. 24, no 11, 1723-1729 p.Article 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.

Place, publisher, year, edition, pages
2003. Vol. 24, no 11, 1723-1729 p.
Keyword [en]
Capillary electrophoresis, Flow injection, Hyphenation, On-column electrode, Poly(dimethylsiloxane)
National Category
Chemical Sciences
Identifiers
URN: urn:nbn:se:uu:diva-94267DOI: 10.1002/elps.200305362OAI: oai:DiVA.org:uu-94267DiVA: diva2:168058
Available from: 2006-04-07 Created: 2006-04-07 Last updated: 2011-12-09Bibliographically approved
In thesis
1. Electrochemical Aspects of Miniaturized Analytical Platforms
Open this publication in new window or tab >>Electrochemical Aspects of Miniaturized Analytical Platforms
2003 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

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

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

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

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

Place, publisher, year, edition, pages
Uppsala: Acta Universitatis Upsaliensis, 2003. 42 p.
Series
Comprehensive Summaries of Uppsala Dissertations from the Faculty of Science and Technology, ISSN 1104-232X ; 810
Keyword
Analytical chemistry, electrochemical detection, microanalytical systems, on-chip CE, ESI, Analytisk kemi
National Category
Analytical Chemistry
Research subject
Analytical Chemistry
Identifiers
urn:nbn:se:uu:diva-3297 (URN)91-554-5536-0 (ISBN)
Public defence
2003-03-28, BMC:B41, Uppsala, 10:15
Opponent
Available from: 2003-03-07 Created: 2003-03-07 Last updated: 2011-12-09Bibliographically approved
2. Development of Micro Liquid Separation Techniques using Electrospray Ionisation Mass Spectrometry in the Analysis of Polar Compounds and Proteins/Peptides
Open this publication in new window or tab >>Development of Micro Liquid Separation Techniques using Electrospray Ionisation Mass Spectrometry in the Analysis of Polar Compounds and Proteins/Peptides
2003 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

Electrospray ionisation (ESI) coupled to mass spectrometry (MS) is one of the most important detection techniques for chemical analysis of small drugs as well as large biomolecules in life science today. In this thesis, aspects on improved compatibility between liquid based separation systems and mass spectrometric detection were investigated regarding buffers, sample preparation and analysis of polar compounds as well as peptides and protein digests for enhanced ESI-MS performance.

Capillary electrophoresis (CE) coupled to ESI-MS detection, was evaluated using both a sheath flow interface and a sheathless design. The separation of peptides and small, polar compounds was optimised for both CE-ESI interfaces. The effect of sheath liquid composition was also studied with the aim to improve sensitivity in the ESI-MS detection.

Polar compounds were retained and separated by capillary ion-pair chromatography coupled to ESI-MS detection. Since commonly used ion-pairing reagents are detrimental to the ESI process they were effectively removed before the ionisation by the use of a trapping column after the separation. Alternatively, the ion-pairing reagents were exchanged to volatile constituents.

A method for peptide mapping by liquid chromatography (LC)-ESI-MS was developed for lactate dehydrogenase. The method was further enhanced to involve the proteolysis on-line to the LC-ESI-MS. No manual sample handling was then needed and the total analysis time decreased from 7 to 1.5 hours. The amount of information was also shown to increase in the on-line system.

Finally, the on-line concept was extended to an innovative interface for direct coupling of a pumped liquid flow to an electroosmotically driven flow. This provided a valve-free sample transfer between capillary LC and CE, aiming towards increased peak capacity per unit time for the analysis of complex peptide samples.

Place, publisher, year, edition, pages
Uppsala: Acta Universitatis Upsaliensis, 2003. 46 p.
Series
Comprehensive Summaries of Uppsala Dissertations from the Faculty of Science and Technology, ISSN 1104-232X ; 808
Keyword
Analytical chemistry, Analytisk kemi
National Category
Analytical Chemistry
Research subject
Analytical Chemistry
Identifiers
urn:nbn:se:uu:diva-3304 (URN)91-554-5534-4 (ISBN)
Public defence
2003-03-21, B21, Uppsala University, Uppsala, 10:15
Opponent
Available from: 2003-02-25 Created: 2003-02-25 Last updated: 2011-12-09Bibliographically approved
3. Integrated Micro-Analytical Tools for Life Science
Open this publication in new window or tab >>Integrated Micro-Analytical Tools for Life Science
2005 (English)Doctoral 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.

Place, publisher, year, edition, pages
Uppsala: Acta Universitatis Upsaliensis, 2005. 57 p.
Series
Digital Comprehensive Summaries of Uppsala Dissertations from the Faculty of Science and Technology, ISSN 1651-6214 ; 112
Keyword
Analytical chemistry, Microdialysis, Multidimensional separation, Liquid chromatography (LC), Capillary electrophoresis (CE), Electrospray ionisation (ESI), Mass spectrometry (MS), Microchip device, Free drug concentration, Screening of microdialysates, Pattern recognition, Analytisk kemi
National Category
Analytical Chemistry
Identifiers
urn:nbn:se:uu:diva-6049 (URN)91-554-6383-5 (ISBN)
Public defence
2005-11-25, B42, BMC, Husargatan 3, Uppsala, 10:15
Opponent
Supervisors
Available from: 2005-10-28 Created: 2005-10-28 Last updated: 2011-12-09Bibliographically approved
4. Microfluidic Devices for Manipulation and Detection of Beads and Biomolecules
Open this publication in new window or tab >>Microfluidic Devices for Manipulation and Detection of Beads and Biomolecules
2006 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

This thesis summarises work towards a Lab-on-Chip (LOC). The request for faster and more efficient chemical and biological analysis is the motivation behind the development of the LOC-concept.

Microfluidic devices tend to become increasingly complex in order to include, e.g. sample delivery, manipulation, and detection, in one chip. The urge for smart and simple design of robust and low-cost microdevices is addressed and discussed.

Design, fabrication and characterization of such microdevices have been demonstrated using low-cost polymer and glass microfabrication methods. The manufacturing is feasible, to a large extent, to perform outside the clean-room, and has subsequently been the chosen technique for most of the work. Issues of bonding reliability are solved by using polymer adhesive tapes.

A planar electrocapture device with LOC-compatibility is demonstrated where beads are immobilised and released in a flowing stream. Retention of nanoparticles by means of electric field-flow fractionation using transparent indium tin oxide electrodes is presented. Moreover, a cast PDMS 4-way crossing is enabling a combination of liquid chromatography and capillary electrophoresis to enhance separation efficiency. Sample transport issues and a new flow-cell design in a quartz crystal microbalance bioanalyzer are also investigated. Fast bacteria counting by impedance measurements, much requested by the pharmaceutical industry for biomass monitoring, is carried out successfully.

In conclusion, knowledge in micro system technology to build microdevices have been utilised to manipulate and characterise beads and cells, taking one step further towards viable Lab-on-Chip instruments.

Place, publisher, year, edition, pages
Uppsala: Acta Universitatis Upsaliensis, 2006. 43 p.
Series
Digital Comprehensive Summaries of Uppsala Dissertations from the Faculty of Science and Technology, ISSN 1651-6214 ; 166
Keyword
Engineering physics, sensor, micro, dielectrophoresis, impedance, electrode, beads, cell, flow, bacteria, microfabrication, biosensor, electrocapture, microfluidic, planar, Lab on chip, µTAS, micro total analysis system, QCM, dispersion, field-flow fractionation, ITO, design, fabrication, Teknisk fysik
National Category
Engineering and Technology
Identifiers
urn:nbn:se:uu:diva-6746 (URN)91-554-6523-4 (ISBN)
Public defence
2006-04-28, Siegbahnsalen, Ångströmlaboratoriet, Lägerhyddsvägen1, Uppsala, 10:00 (English)
Opponent
Supervisors
Available from: 2006-04-07 Created: 2006-04-07 Last updated: 2011-12-09Bibliographically approved

Open Access in DiVA

No full text

Other links

Publisher's full text

Authority records BETA

Bergström, Sara K.Wetterhall, Magnus

Search in DiVA

By author/editor
Bergström, Sara K.Wetterhall, Magnus
By organisation
Analytical ChemistrySolid State Electronics
In the same journal
Electrophoresis
Chemical Sciences

Search outside of DiVA

GoogleGoogle Scholar

doi
urn-nbn

Altmetric score

doi
urn-nbn
Total: 1327 hits
CiteExportLink to record
Permanent link

Direct 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