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Sample preconcentration in open micro channels
KTH, School of Chemical Science and Engineering (CHE).
2011 (English)Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesisAlternative title
Förkoncentrering i öppna mikrokanaler (Swedish)
Abstract [en]

Preconcentration is necessary in order to be able to detect analytes in low-concentration samples, when there are only limited amounts of sample available, and/or when detection limits are not sufficiently low.

A preconcentration platform has been under development in the Division of Analytical Chemistry at KTH. The sample preconcentration is performed using electromigration of analytes in open channels on a microchip. An advantage of this system is the possibility of coupling it to other techniques as part of a larger analysis scheme.

In previous research it has been concluded that the electrochemistry of this system is complex, and that water electrolysis results in formation of a pH gradient in the micro channel.

The nature of the pH gradient has been studied in this work; firstly in a closed system of approximately the same dimensions as the micro channel, to eliminate the additional parameter of fast evaporation from the open channel. It could be shown that the position of a preconcentrated protein in the closed capillary was affected by the pH gradient. The position depends on the initial solution pH and the preconcentration time.

Next, these experiments were transferred to the microchip and preconcentration in an open channel was studied. Through continuously adding sample to the channel, the solvent evaporation from the open channel could be used in preconcentrating the analyte. Continuous supply of sample did not eliminate the pH gradient but reduced it to some extent.

Finally, matrix-assisted laser desorption/ionization (MALDI) analysis with the open channel as a detection window was performed. Cytochrome c was preconcentrated through continuously supplying low-concentration sample and promising results were obtained. The position of the preconcentrated zone was in agreement with and could be explained by previous observations.


Place, publisher, year, edition, pages
Keyword [en]
Preconcentration, silicon chip, open channels, pH gradients, matrix assisted laser desorption/ionization
National Category
Analytical Chemistry
URN: urn:nbn:se:kth:diva-33275OAI: diva2:414032
Subject / course
Analytical Chemistry
Educational program
Master of Science in Engineering - Chemical Science and Engineering
Physics, Chemistry, Mathematics
Available from: 2011-05-02 Created: 2011-05-02 Last updated: 2011-06-22

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