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Poly(dimethylsiloxane)-Based Microchip for Two-Dimensional Solid-Phase Extraction-Capillary Electrophoresis with an Integrated Electrospray Emitter Tip
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 Medicine and Pharmacy, Faculty of Pharmacy, Department of Pharmaceutical Biosciences, MMS, Medical Mass Spectrometry.
Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry, Analytical Chemistry.
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2005 (English)In: Analytical Chemistry, ISSN 0003-2700, E-ISSN 1520-6882, Vol. 77, no 16, 5356-5363 p.Article 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.

Place, publisher, year, edition, pages
2005. Vol. 77, no 16, 5356-5363 p.
National Category
Chemical Sciences
Identifiers
URN: urn:nbn:se:uu:diva-74074DOI: 10.1021/ac050495gPubMedID: 16097780OAI: oai:DiVA.org:uu-74074DiVA: diva2:101985
Available from: 2005-08-26 Created: 2005-08-26 Last updated: 2017-12-14Bibliographically approved
In thesis
1. Microscale Tools for Sample Preparation, Separation and Detection of Neuropeptides
Open this publication in new window or tab >>Microscale Tools for Sample Preparation, Separation and Detection of Neuropeptides
2005 (English)Doctoral thesis, comprehensive summary (Other academic)
Alternative title[sv]
Mikroskaliga verktyg för provpreparering, separation och detektion av neuropeptider
Abstract [en]

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

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

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

Place, publisher, year, edition, pages
Uppsala: Kemiska institutionen, 2005. 62 p.
Series
Digital Comprehensive Summaries of Uppsala Dissertations from the Faculty of Science and Technology, ISSN 1651-6214 ; 64
Keyword
Analytical chemistry, Neuropeptides, Microchip, Enhanced microdialysis, Poly(dimethylsiloxane) (PDMS), Electrospray ionization (ESI), Multidimensional separation, Electrochemical manipulation, Mass spectrometry (MS), Capillary electrophoresis (CE), Microdevice, Microfabrication, Micro total analysis system (μ-TAS), Analytisk kemi
National Category
Analytical Chemistry
Identifiers
urn:nbn:se:uu:diva-5838 (URN)91-554-6279-0 (ISBN)
Public defence
2005-06-03, Room B42, BMC, Uppsala, 10:15
Opponent
Supervisors
Available from: 2005-05-10 Created: 2005-05-10 Last updated: 2011-12-08Bibliographically approved
2. 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

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Dahlin, Andreas P.Bergström, Sara K.Andrén, Per E.Bergquist, Jonas

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