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Efforts to improve detection sensitivity for capillary electrophoresis coupled to atmospheric pressure photoionization mass spectrometry.
Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Physical and Analytical Chemistry.
Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Physical and Analytical Chemistry.
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2010 (English)In: Rapid Communications in Mass Spectrometry, ISSN 0951-4198, E-ISSN 1097-0231, Vol. 24, no 9, 1260-1264 p.Article in journal (Refereed) Published
Abstract [en]

Electrospray ionization performs best with volatile buffers. However, generally the best separation performance for capillary electrophoresis (CE) is achieved with non-volatile buffers. Hyphenation of CE with mass spectrometry (MS) utilizing atmospheric pressure photoionization (APPI) enables use of a wider range of separation buffers without compromising detection sensitivity. As APPI is considered to be mass flow sensitive, the use of a larger inner diameter separation capillary (75 microm) allows larger volumes to be injected, without decreased separation performance, thus providing improved sensitivity (approx. a factor of 10), compared to the use of a 25 microm capillary. However, nebulizing gas flow and position of capillary tip in the sprayer have to be carefully optimized to prevent excessive band broadening. Further improvement in sensitivity (approx. a factor of 2) was obtained by decreasing the distance between the sprayer and ionization region, indicating that a specially designed CE/APPI-MS interface for low flow rates will be favourable.

Place, publisher, year, edition, pages
John Wiley & Sons Ltd , 2010. Vol. 24, no 9, 1260-1264 p.
National Category
Analytical Chemistry
Research subject
Analytical Chemistry
Identifiers
URN: urn:nbn:se:uu:diva-122426DOI: 10.1002/rcm.4510ISI: 000277352700006PubMedID: 20391596OAI: oai:DiVA.org:uu-122426DiVA: diva2:310080
Available from: 2010-04-12 Created: 2010-04-12 Last updated: 2013-01-02Bibliographically approved
In thesis
1. Nanoparticles in capillary electrophoresis: what are the benefits?
Open this publication in new window or tab >>Nanoparticles in capillary electrophoresis: what are the benefits?
2011 (English)Licentiate thesis, comprehensive summary (Other academic)
Abstract [en]

Capillary electrophoresis is a technique that separate compounds based on charge and size. During the last two decades capillary electrophoresis (CE) and mass spectrometry (MS) has gained in interest, become more robust to use and able to separate neutral analytes. The separation of neutral analytes was first achieved with packed columns, but several disadvantages can be obtained with a stationary phase and the method of packing capillaries. Therefore, pseudostationary phases became a good alternative. The risk of clogging, memory effects and lower efficiency could be minimized with pseudophases. However, since mass spectrometry has become the most important analytical detector, and play a key role in the search for biomarkers in clinical applications, it is important that CE can successfully be combined with MS. To obtain this hyphenation several types of interfaces for the vital ion source exist. In paper I an atmospheric pressure photoionization interface was investigated in order to accomplish an improved detection sensitivity. The knowledge attained with this type of interface could then be transferred to the one used in paper II, the electrospray ionization interface (ESI), where the use of a MS friendly nanoparticle based pseudostationary phase was investigated. Both studies showed that it is still possible to improve the separation technique and modify the ion source in order to improve the detection sensitivity for capillary electrophoresis hyphenated with mass spectrometry.

Place, publisher, year, edition, pages
Uppsala: Institutionen för fysikalisk och analytisk kemi, Uppsala universitet, 2011
National Category
Chemical Sciences
Identifiers
urn:nbn:se:uu:diva-147008 (URN)
Supervisors
Available from: 2011-02-24 Created: 2011-02-23 Last updated: 2011-03-16Bibliographically approved
2. Interfacing Complementary Separation Techniques with Mass Spectrometry Utilizing Electrophoresis, Nanoparticles, and Functionalized Magnetic Beads
Open this publication in new window or tab >>Interfacing Complementary Separation Techniques with Mass Spectrometry Utilizing Electrophoresis, Nanoparticles, and Functionalized Magnetic Beads
2012 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

Capillary electrophoresis (CE) has during the last two decades become more robust and been able to separate neutral analytes without compromising the downstream detection. An interesting aspect in CE compared to more commonly used high-performance liquid chromatography is the orthogonal separation mechanism provided by CE. Compounds are separated based on charge and size with extremely high separation efficiencies. However, since mass spectrometry (MS) has become one of the most important analytical detectors and play a key role for pharmaceutical- and in clinical applications it is of major importance that the two techniques successfully can be combined without any compromises. Improvements in existing ion sources must be made in order to fully take advantage of the potential in capillary electrophoresis and mass spectrometry. One way is to miniaturize the ion source (paper I) in order to make it more compatible with the smaller liquid volumes and lower flow rates in CE. Despite these improvements challenges such as low sample concentrations, non-separated peaks, unspecific losses, and poor ionization still remain, and are addressed in this doctoral thesis.

Separation of neutral analytes has previously been achieved with packed columns but with several disadvantages. Therefore, MS-compatible pseudostationary phases in the form of nanoparticles (paper II) are an interesting alternative with its minimized risk of clogging, reduced memory effects and better separation efficiencies. Particles or beads have also shown to be of importance when reducing the dynamic range in complex samples. By creating functionalized magnetic beads (paper III), complex samples such as human plasma can be fractionated in the manner that low molecular weight proteins are selectively enriched. Despite fractionation and enrichment of analytes of interest (paper IV) the ionization suppression could lead to biased sensitivity, increased baseline, retention variations and chromatographic distortion. Therefore the separation, as well as the ionization, is of major importance. For instance, in order to separate and detect monoclonal antibodies, which are an upcoming class of biotherapeutic drugs, the choice of capillary temperature and sheath liquid composition must be considered due to its major influence on charge state, peak intensity and memory effects (paper V).

Place, publisher, year, edition, pages
Uppsala: Acta Universitatis Upsaliensis, 2012. 63 p.
Series
Digital Comprehensive Summaries of Uppsala Dissertations from the Faculty of Science and Technology, ISSN 1651-6214 ; 993
National Category
Analytical Chemistry
Identifiers
urn:nbn:se:uu:diva-183666 (URN)978-91-554-8529-0 (ISBN)
Public defence
2012-12-14, B42, Husargatan 3, Uppsala, 10:15 (English)
Opponent
Supervisors
Available from: 2012-11-22 Created: 2012-10-31 Last updated: 2013-02-11Bibliographically approved

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Malmström, DavidSjöberg, Per J. R.

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